Tag Archives: rain

Messy Winter Storm Monday Night Into Tuesday

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Hello everyone!

This evening’s update will focus on an impactful and messy winter storm forecast to move through the area Monday night into Tuesday. It will bring with it copious amounts of all precip types with significant snow in the far north, sleet and freezing rain for most, and heavy rain along the shorelines.

12Z 3km NAM Showing Light Flurries Tomorrow Night. Credit: Weatherbell
12Z 3km NAM Showing Light Flurries Tomorrow Night. Credit: Weatherbell

The event will technically begin tomorrow during the afternoon as shifting winds aloft bring some light moisture into the area. The greatest chance for precip will be across southern areas where some ocean moisture will become entrained in the NE winds and also in the mountains where some upsloping will aid in precip development. Precip will fall as sprinkles of the liquid variety along the southern coast, flurries in the mountains, and pockets of sleet/freezing rain across interior SW NH. No accumulation is expected but some slick spots are possible here or there.

18Z NAM Vertical Slice Compilation Tomorrow Evening. Image Credit: Accuweather
18Z NAM Vertical Slice Compilation Tomorrow Evening. Image Credit: Accuweather

Shown to the left is a series of maps that holds the key to this forecast. The model and time are kept the same with each map displaying a forecast for a different slice of the atmosphere. The top forecast is for about 25,000 feet followed by 10,000, 5,000, 2500, and 0 feet. The feature of interest is a back door cold front moving SW across the area tomorrow evening. Notice how it slopes backward over the cold airmass with the most forward progress of the cold wedge at the surface and the least progress aloft. This sets up a situation where you have a deep cold intrusion at the surface (and a high pressure system over Quebec to lock it in) and an environment only marginally cold aloft. This sets up a situation where warm air can easily flood in aloft but will have a hard time making headway at the surface. This is why we’re in for more freezing rain/sleet than snow for most of the area. The best chance for sizeable snowfall accumulation will be the far NW mountains. The poleward slope of the cold frontal surface illustrated above means that we’ll have an excellent isentropic overrunning surface as warm air is forced to glide up and over the low-level cold dome.

18Z NAM NB-VA Cross Section Showing A Well Defined Poleward Sloping Cold Frontal Surface. Image Credit: Accuweather
18Z NAM NB-VA Cross Section Showing A Well Defined Poleward Sloping Cold Frontal Surface. Image Credit: Accuweather

Here’s a cross section showing another view of the same phenomenon we discussed above. Because of the discrepancy between airmasses, this boundary acts similarly to a material surface along which air will rise. This sets up the arrival of precip Monday evening, initially as snow due to the deep cold air. You can see the warm nose moving in from the SW on the cross-section, it’s the little kink to the right in the purple (0C) line. That’s the warm air riding up and over our cold front. The image is valid 1 AM Monday morning. Also notice the low-level moisture on the cold side of the front. This is why we’ll see some light flurries/sprinkles/drizzle Sunday night and Monday morning.

Now that we’ve established that we’re looking at an elevated warm layer and a near surface cold layer, let’s look at a sounding (vertical profile of the atmosphere at a single point) to determine if we’re looking at inches of sleet or a damaging ice storm.

12Z NAM Sounding For Lewiston At 7AM Tuesday
12Z NAM Sounding For Lewiston At 7AM Tuesday

Thankfully for the power grid, the cold layer near the surface looks deep enough to allow for sleet to be the dominant precip type. While the deep warm layer will melt snowflakes, the deep cold layer near the surface will allow for those raindrops to refreeze into ice pellets rather than freeze on contact with the ground. That’s not to say that some folks won’t see ice accumulation but it likely won’t be heavy enough to cause power outage issues. Don’t worry though, we have winds for that job along the coast. For more on how warm/cold layers impact precip type, check out one of my recent UpPortland columns where I explain various forms hydrometeors make their way to the ground.

NAEFS Ensemble U-Vector Anomaly Tuesday Morning Showing Anomalously Strong East Winds At 850mb. Image Credit: NWS/NOAA
NAEFS Ensemble U-Vector Anomaly Tuesday Morning Showing Anomalously Strong East Winds At 850mb. Image Credit: NWS/NOAA

Here’s a look at the mid level winds which will be very strong out of the east/south east. The map to the left shows the anomaly in the u vector which is the east/west component of the wind. The highly negative u vector means the easterly component of the wind will be exceptionally strong. This will help not only to bring warm air into the region aloft, but it will also help introduce the threat for gusty winds out of the east along the midcoast early Tuesday morning.

18Z NAM Showing Strong Winds For The Midcoast And Southern Shorelines Tuesday Morning. Image Credit: Weatherbell
18Z NAM Showing Strong Winds For The Midcoast And Southern Shorelines Tuesday Morning. Image Credit: Weatherbell

Winds will be an issue along the midcoast and any other shoreline towns that happen to make it into the maritime airmass E of the coastal front. Wind gusts of 40-45mph are likely for a time Tuesday morning as low pressure approaches. On the western side of the coastal front, look for cold but lighter N/NE breezes to keep cold air locked in place at the surface resulting in slippery travel and messy precip types.

12Z NAM Showing Gusty Winds Just Above The Surface In Rockland Tuesday Morning
12Z NAM Showing Gusty Winds Just Above The Surface In Rockland Tuesday Morning

Here’s another view of the wind potential as shown by a vertical cross-section through time above Rockland. Notice the strong low-level jet just off the surface. Any winds below the yellow line are ‘eligible’ to be mixed down to the surface via momentum transfer and as a result, there is fairly high confidence in 40-45mph gusts along the midcoast Tuesday morning. For more on momentum transfer, check out one of my UpPortland columns from a while back where I explain it.

Tide Forecast For Portland Through Wednesday Morning. Image Credit: NWS/NOAA
Tide Forecast For Portland Through Wednesday Morning. Image Credit: NWS/NOAA

All those easterly winds over the Gulf of Maine will push water up along the coast. While thankfully we’re not experiencing astronomically high tides, some splashover is possible as shown by the black total water level forecast above the first red line which is mean higher high water level. The specifics of that value are complicated but you should know the little yellow line (storm surge) will be between 1 and 2 feet and will push water high enough for some minor coastal flooding though no major impacts are expected.

Precip Type Forecast For Monday Night Through Tuesday
Precip Type Forecast For Monday Night Through Tuesday

Here are my thoughts on precip type. Rain will be confined to the midcoast/shorelines and most of the area will see sleet for most of the event after an initial thump of snow. During that initial thump, 2-4″ can be expected for most. An additional few inches up in the northern mountains will likely bring totals to the 4-8″ range in the blue zone on the map above.

18Z GFS Showing Another Round Of Light Precip Wednesday Evening. Image Credit: Weatherbell
18Z GFS Showing Another Round Of Light Precip Wednesday Evening. Image Credit: Weatherbell

Precip moves out Tuesday evening and we’ll be left with a relatively mild airmass and dry weather for about 24 hours before another system approaches from the west. This one will be much weaker and is likely to bring just a brief period of snow/mix to the mountains with rain showers in the south. Little to no accumulation is forecast but some slick spots will once again be likely. Behind this system, colder air will begin working back into the region as winter’s comeback begins.

More tomorrow after I enjoy some turns up at Sunday River. As a result, tomorrow’s update may be a little later in the evening but will contain all the latest analysis.

-Jack

Showers Bring Heavy Rain Tonight Before Cooler And Drier Conditions Early Week

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Hello everyone!

A cold front is incoming this evening and will cross the area tonight and early tomorrow morning. Showers will accompany this front with heavy rain and possibly a rumble or two in the far south. No severe weather is expected, just heavy rain. Rain will be heaviest in the north where up to an inch is expected. It will be lightest in the south where some areas may only pick up a quarter inch. Rain races NE Monday morning with clearing skies and gusty NW winds Monday during the day. Those NW winds will bring much cooler and much drier air in for Tuesday and Wednesday. An approaching front will bring SW winds and warmer air for late week with showers possible by the upcoming weekend. Just as a reminder, current information on tropical weather is now on the new tropical weather page.

4:00 PM Observations Verifying Today's Forecast
4:00 PM Observations Verifying Today’s Forecast

Today’s forecast worked out pretty well and the only glaring error was that there was more sunshine than expected. So far I haven’t received any complaints about that! Clouds are still slowly filtering in from the west while the Midcoast got their predicted marine fog. Temps look good with the only glaring error being lower temps (60’s) along the midcoast where the fog hasn’t let up. I have doubts about the 88 degree reading in Concord as no other station in that area is above the low 80’s but if that is actually accurate, that would be the other mistake as far as temps go. Overall, I’m pretty pleased with today’s forecast.

8 AM Upper Air Observations Showing The Overall Pattern. Image Credit: Meteocentre
8 AM Upper Air Observations Showing The Overall Pattern. Image Credit: Meteocentre

A deep trough is located over the Great Lakes this evening with an associated surface low near the SE corner of Hudson Bay. Ahead of the trough, strong blocking ridging exists over the Canadian Maritimes. In between, SW flow is bringing warm moist air northward. Strong NW flow behind the trough and attendant front will bring cool, dry air sourced from Northern Canada before SW winds ahead of the digging trough in the Pacific NW bring warmer air for the upcoming weekend.

HRRR With An Idea Of What The Radar Might Look Like Early Tomorrow Morning. Image Credit: Weatherbell
HRRR With An Idea Of What The Radar Might Look Like Early Tomorrow Morning. Image Credit: Weatherbell

In terms of what to expect tonight, showers are just now moving into far Western VT which means that western NH will start to see drops in 2-3 hours. It won’t be until well after dark that western Maine starts to see the rain move in. The rain will be associated with a single N/S band containing heavy rain and possibly a rumble or two in the far south. The band will be wider and heavier in northern areas resulting in higher totals there. The HRRR map above illustrates the setup well. The map is valid at 4:00 tomorrow morning. Rain will move out of Portland by 6 AM and out of the midcoast by 8. Clearing will follow.

12Z GFS Showing Gusty NW Winds Tomorrow. Image Credit: Weatherbell
12Z GFS Showing Gusty NW Winds Tomorrow. Image Credit: Weatherbell

Behind the front, gusty NW winds are forecast to develop. Winds could gust over 30mph at times as cooler and drier air works into the region. Look for these winds to quickly downslope the coast to sunny skies while upsloping may postpone sunshine for the mountains. Eventually, the air will become so dry that even with upsloping, the mountains will become sunny by afternoon. Dew points are forecast to drop to near 40 by tomorrow night. As winds settle down tomorrow night, temps will fall too. By Tuesday morning, the first fall like chills will be felt with temps bottoming out right around 40 in the north and 50 in the south with very dry air.

12Z GFS Showing Warm SW Winds Ahead Of An Approaching Front Late Next Week. Image Credit: Weatherbell
12Z GFS Showing Warm SW Winds Ahead Of An Approaching Front Late This Week. Image Credit: Weatherbell

Not ready for fall? Not to worry. By late in the week a front will be approaching from the NW and ahead of it SW winds will bring in slowly increasing warmth as well as humidity. While conditions won’t be stifling, the word sticky will once again come to mind by the upcoming weekend. As far as precip goes, the front won’t have a lot of dynamics associated with it and so scattered showers/storms are likely the most we’ll get from that front. After that, dry and warm conditions are likely to kick off next week.

Be sure to check out the new tropical weather page to keep tabs on the Atlantic disturbances 90L and 99L without the hype you may see on social media. The official NHC forecast, my forecast, and links to all the tropical weather information you need to take your own look at the tropics is all there. Check it out!

-Jack

First Fall Like Front Of The Season To Bring Heavy Rains Sunday Night

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Hello everyone!

It’s beginning to look a lot like fall in terms of the weather pattern. A strong upper level disturbance is digging south into the northern Plains states and ahead of it seasonably strong low pressure will develop driving a fairly strong cold front into the area Sunday night into Monday morning. During this time, showers and a few storms are likely to drop some beneficial rains. Cool, dry, awesomely comfortable air will settle in as strong high pressure builds overhead for Tuesday through Thursday. After Thursday, the high moves offshore and an approaching front will bring more warm air into the region before more showers and storms at some point next weekend.

3:00 PM Observations Verifying Today's Forecast
3:00 PM Observations Verifying Today’s Forecast

Today’s forecast worked out well with dry conditions, sunny skies, and light NW breezes. A sea breeze has developed along the coast bringing slightly cooler temps there. Temps are currently ranging from the mid 70’s north to the mid/upper 80’s south which is right in line with the forecast. This is one of those straightforward days where not a whole lot can/did go wrong in terms of the forecast. Days like this are a rarity in Maine!

Current WV Satellite Showing The Upper Air Players On The Field This Afternoon. Image Credit: Weatherbell
Current WV Satellite Showing The Upper Air Players On The Field This Afternoon. Image Credit: COD

The upper air setup looks a lot like fall with a deep trough beginning to evolve to our west. This trough will continue to strengthen and begin to tilt negatively as it moves east. Ahead of the trough, a ridge will build, slowing the eastern progress of the trough. This ridge does not look as strong as once modeled and thus the front is likely to keep moving a little faster than it looked a couple of days ago. Regardless of speed, a line of tropical downpours is likely ahead of the front. The heaviest rain will be over northern areas where better upper level dynamics are likely.

12Z GFS Showing Tropical Moisture Streaming North And Dry Canadian Air Streaming South Sunday Night. Image Credit: Weatherbell
12Z GFS Showing Tropical Moisture Streaming North And Dry Canadian Air Streaming South Sunday Night. Image Credit: Weatherbell

The weather for the next several days can be seen in this map of moisture from the GFS. Increasing clouds and moisture ahead of the front tomorrow and to a larger degree Sunday will result in lower temps but dew points will be on the rise leading to more humidity. That humidity will fuel tropical downpours along the front before dry Canadian air sweeps south bringing comfortable humidity back. How do dew points in the 40’s sound? Yeah, that’s happening Tuesday and Wednesday.

12Z GFS Showing A Warming Trend Heading Into Next Weekend. Image Credit: Weatherbell
12Z GFS Showing A Warming Trend Heading Into Next Weekend. Image Credit: Weatherbell

The significant heat relief will be short lived as SW breezes bring warmer and more humid conditions into the region late next week. A frontal boundary will sag south during this time crossing the area at some point this weekend with more showers and storms possible. The timing of this remains uncertain. While temps and dew points will be higher than Tuesday and Wednesday, they still don’t look oppressive. The true dog days of summer may be numbered.

2PM NHC Tropical Weather Outlook. Credit: NHC
2PM NHC Tropical Weather Outlook. Credit: NHC

I want to end with a quick note on the tropics. There is a cluster of thunderstorms over the open ocean roughly half way between the Caribbean and Africa. Some computer model guidance has indicated that this cluster will evolve into a tropical storm that could threaten the US. It is important to note that this tropical storm that some models predict hasn’t formed yet. This means that the models are having a hard time figuring out what it is right now (models don’t often “see” thunderstorms as they actually are because thunderstorms are almost always too small for the model’s grid points). The pattern is favorable for this cluster of storms to develop gradually and the NHC has given it a 50% chance to develop in the next 5 days.

Computer Model Spaghetti Plot Showing Considerable Uncertainty In Track After A Couple Days. Image Credit: Weatherbell
Computer Model Spaghetti Plot Showing Considerable Uncertainty In Track After A Couple Days. Image Credit: Weatherbell

This does not mean that the computer model maps showing a large hurricane over *insert US city here* have any merit. If you are taking a vacation to Puerto Rico, Barbados, or any of the other eastern Caribbean islands in the next week, keep an eye on this system. Otherwise, this is not something to worry about. Should that change as the system moves west, I’ll be sure to let you know. Please don’t fall for model hype that can be found on social media. As always, continue to keep tabs on the forecast through the official NWS channels such as the National Hurricane Center and the local NWS office in Gray.

More info tomorrow.

-Jack

Rain Heavy At Times Tonight

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Hello everyone!

Showers are moving in this evening and will continue to do so through the overnight hours. Rain will be heavy at times and steadiest in the northern part of the mountains. The rest of the area will see more scattered heavy rain with thunder and gusty winds possible in the stronger cells. Showers and storms sweep east tomorrow morning with clearing in the afternoon. A few showers are possible Thursday with the passage of a cold front but otherwise the end of the week and the weekend look warm and dry. Another threat for heavy rain arrives early next week with significant heat relief likely following for the rest of next week.

4:30 PM Observations Verifying Today's Forecast. Credit: EDD
4:30 PM Observations Verifying Today’s Forecast. Credit: EDD

Today’s forecast was fairly good. Morning sun slowly faded behind increasing clouds and showers began encroaching from the west this afternoon. Temps stayed mainly in the 70’s as forecast with only a few low 80’s in far southern NH. The showers arrived a hair earlier than forecast and continue to do so this evening but the margin of error there was fairly small. Again, there is no such thing as a perfect forecast but today’s was fairly solid.

4PM Surface Observations Showing The Surface Setup For Tonight. Image Credit: SPC Mesoscale Analysis
4PM Surface Observations Showing The Surface Setup For Tonight. Image Credit: SPC Mesoanalysis

A round of rain ahead of a warm front is moving NE through the area currently. The warm front will lift north before stalling right around Portland tonight. Meanwhile, low pressure will track through the mountains during the same overnight timeframe before pushing a cold front south early tomorrow morning. This is the surface setup and is shown with the 4PM surface analysis map from the SPC mesoanalysis page. The biggest forecast challenge for tonight will be pinpointing exactly where that warm front sets up. North of it, steady heavy rains will put a noticeable dent in the drought. South of it, heavy rains will be hit or miss in a more convective format with some towns getting a much needed drink and others staying more or less completely dry.

4PM Middle Atmosphere (850mb) Analysis Showing A Plume Of Moisture Headed Our Way. Image Credit: SPC Mesoanalysis
4PM Middle Atmosphere (850mb) Analysis Showing A Plume Of Moisture Headed Our Way. Credit: SPC Mesoanalysis

Aloft, a disturbance over the Eastern Great Lakes will move rapidly NE tonight. SW winds ahead of this disturbance will pump a warm moist airmass into the region. This airmass will feature more Precipitable Water values in excess of 2″ which will support very heavy rain. Pictured is the 850mb moisture field (RH) and vectors showing where that moisture is going (arrows). Notice all the arrows pointing in our direction. This shows that the moisture is headed our way overnight tonight.

HRRR Showing One Idea As To How Things Play Out Tonight. Credit: Weatherbell
HRRR Showing One Idea As To How Things Play Out Tonight. Credit: Weatherbell

So what does this all mean for the forecast tonight into tomorrow morning? The HRRR model does a fairly good job summing it up. Rain will continue to overspread the region from SW to NE this evening and will become heavy at times. The heaviest rain will be concentrated over northern areas with the cutoff somewhere between Portland and Lewiston. North of that cutoff point, steady rain, heavy at times, can be expected with storm totals of 1-2″. Some areas have a shot at seeing up to 3″ if they can manage to sit under a downpour for a while. South of that cutoff, heavy rain will be more scattered with those same 1-2″ amounts falling only where the heaviest downpours track. Those that don’t see individual storms track overhead are likely to miss out on any substantial rain. Most areas in this southern region will see between a tenth and a third of an inch of rain with some spots under the heaviest downpours seeing amounts closer to an inch or two.

Some of the downpours over southern areas could feature thunder and gusty winds as some marginal instability tries to work in aloft. This will not be a widespread severe event but some gusty winds are possible especially across SW NH. The bigger severe threat is to our SW over SNE and NY but we will get some of those storms in a much weakened state. Be aware and have a plan if a warning is issued for your area but otherwise, this won’t be a significant event. Showers and storms sweep NE tomorrow morning with just a few showers left along the coast by sunrise.

12Z GFS Showing A Weak Cold Front Passing Overhead Thursday
12Z GFS Showing A Weak Cold Front Passing Overhead Thursday

The rest of Wednesday will be mostly dry with just an isolated pop up shower here or there. Temps will be warm but not hot and dew points will be sticky but not oppressive. Another cold front will approach the area Thursday which will bring the chance for some more showers and possibly a storm or two. Notice the two low pressure systems back to the west on this map valid Thursday afternoon. Those will slowly work east during the weekend and will end up near us by Monday with a slow moving cold front in tow.

This Morning's Surface Analysis Showing All The Players For This Week's Weather. Image Credit: Meteocentre
This Morning’s Surface Analysis Showing All The Players For This Week’s Weather. Image Credit: Meteocentre

Next week’s rain threat will be centered around Monday. The upper level pattern will shift by then and the seeds of that shift are being sown today. The thick black line is tonight’s disturbance. Thursday’s disturbance is the red line. The lines for the next heavy rainfall threat are the blue one in the top left over NW Canada, the green one south of Bermuda, and the pink one over the Rockies. The blue disturbance will drop south in the coming days and carve out a deep trough. The pink ridge will move offshore by Monday and will end up evolving into a large block off of Nova Scotia. The southerly flow around this block and ahead of the Canadian disturbance will drag tropical moisture provided by the green disturbance northward. There is no reason to change from last night’s forecast anything except the timing. The amplified pattern means that the forward (eastward) progress of each feature will be slowed. Last night, it looked like the heavy rain threat was primarily Sunday into Monday, now guidance indicates it’s more of a Monday/Tuesday affair. Based on the pattern and guidance trends, don’t be surprised if this ends up being more of a middle of next week event. It is still far too early for specifics but if you have plans around this time, keep updated with latest forecasts both from me as well as the NWS and local media.

The deep trough over the Central US that will be providing the focus for this rain threat looks to move east by late next week with more substantial heat relief. How long will that last? It’s anyone’s guess at this point but that should become clearer as we get closer. There is plenty of weather to figure out between now and then.

-Jack

More Beneficial Rain This Week

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Hello everyone!

After a weekend of on and off storms and heavy rain, we finally got a break from the heat, humidity, and storms today. Enjoy the drier air while it lasts because it won’t last long. Warm, sticky air will again flood the region tomorrow as a warm front tries to drive north. After heavy rain for many tomorrow evening, rain will become lighter and more scattered for the rest of this week with more dry hours than wet. That changes by this upcoming weekend when a deep trough to our west will bring more tropical moisture and accordingly more heavy rain.

5:00 PM Observations Verifying Today's Forecast
5:00 PM Observations Verifying Today’s Forecast

Today’s forecast worked out fairly well with the exception of cloud cover. In typical upslope/downslope situations, the clouds would reside over the mountains while the sun would be over the southern part of the area. Today, however, warm air advection aloft brought clouds to the south while the atmosphere dried out so much (and was still so warm aloft) that no widespread clouds were observed over northern areas. The cloud cover aside, everyone stayed dry as forecast and forecast temps panned out well with mid/upper 70’s north and low to mid 80’s south. Overall, not a disaster, but as always, it could’ve been better.

12Z GFS Showing The Upper Level Setup Tomorrow Evening
12Z GFS Showing The Upper Level Setup Tomorrow Evening

Tomorrow will feature the return of tropical moisture to the area as a disturbance passes through Northern VT and into Northern ME. A low pressure system will move right through the middle of the area tomorrow as well. This means that SW winds aloft and at the surface will again bring tropical moisture to the area. Tomorrow’s forecast will be basically split up into three parts, the delineation between them being location. The first part will be fairly heavy, fairly steady rain across the north.

12Z GFS Showing Tropical Moisture To Fuel Heavy Rains Tomorrow. Credit: Weatherbell
12Z GFS Showing Tropical Moisture To Fuel Heavy Rains Tomorrow. Credit: Weatherbell

Tropical moisture will once again be present across the region by tomorrow afternoon and evening and Precipitable Water values will be running near or over 2″ which is about as loaded as it gets here in Maine in terms of tropical moisture. Low pressure will pass right through the middle of the area leaving the northern part of the area to the north and eventually north west of the low. This is where steady precip is most likely, The tropical moisture will encounter some residual low level cool air leftover from today’s airmass and rise, cool, and condense, causing rain. Areas mainly north of route 2 could see 1-3″ of rain from this event.

12Z 4km NAM Showing One Idea As To How The Storm Could Play Out Tomorrow. Image Credit: Weatherbell
12Z 4km NAM Showing One Idea As To How The Storm Could Play Out Tomorrow. Image Credit: Weatherbell

The middle part of the area, north of a Portland/Hanover NH line, but south of route 2, will see more scattered showers and possibly a storm or two. This is the area through which the low itself will track which means that it will be missing both the instability from the warm sector south of the low, and the forcing for steady rain north of the low. This area will see the least amount of precip overall because it is neither here nor there so to speak. The precip for this middle stripe will range from a quarter to a half inch and will come from showers and storms that form farther south tracking NE.

12Z GFS Showing More Than Enough Shear For Severe Potential Tomorrow. Credit: Accuweather
12Z GFS Showing More Than Enough Shear For Severe Potential Tomorrow. Credit: Accuweather

Southern areas, south of that Portland/Hanover NH line, will see showers and storms with torrential rains and also with some limited severe potential. The nearby low, strong upper level disturbance, and warm front/cold front combo will provide the trigger. Strong shear associated with the developing low (pictured above) will provide the organizer, but the big question will, as per the norm here in Maine, be instability which, right now, looks limited at best. Due to the lack of instability and the presence of an inversion aloft which will help keep strong winds high in the sky, the severe threat looks limited. That being said, the SPC has this southern area in a marginal risk for severe weather and a stray strong wind gust can’t be ruled out. This severe threat will be least small overnight Tuesday into early Wednesday morning. Some scattered showers and possibly a stray storm is possible Wednesday morning before afternoon drying and clearing. Southern areas will see rainfall amounts vary widely depending on exactly where storms set up going into the evening hours. Some places could see over 1-2″ if storms train over a specific location while it is possible others struggle to see even a quarter of an inch of rain. There is no way of knowing exactly where storms will set up this far in advance.

Highs Tuesday look to remain cooler as clouds and showers overspread the area from west to east. Look for temps largely in the 70’s with a few low 80’s possible in SW NH.

Thursday and Friday at least look warm but not hot with some scattered showers in the afternoon but no organized rain. By the beginning of next weekend, however, a deep trough will be present over the Central US with deep S/SE flow from the tropics over our area out ahead of it.

12Z GFS Showing The Pattern For Our Next Rain Threat This Coming Weekend
12Z GFS Showing The Pattern For Our Next Rain Threat This Coming Weekend

There are several important factors for next weekend’s rainfall potential. The pattern looks a lot like last winter’s with a big trough just to our west flanked by large blocking ridges. Warm S/SE flow ahead of the trough looks to bring another threat for heavy rain, just like it did so many times last winter. At this point, all that seems clear is that another heavy rain threat exists and must be watched between 6 and 8 days from now. The pattern supports it as does all available guidance that I’ve seen. Specifics are still uncertain at this point but they will become less so as the week goes on. I’ll have more updates as those details become clearer.

Following that heavy rain threat, more significant heat relief seems likely as we look to move into the third and fourth weeks of August.

One last note, this Wednesday (8/17) at 6:30 PM, I will be giving a presentation at the Freeport Community Library where I will discuss me and my background, some of the quirks of Maine weather, how to be a better informed consumer of weather information, and finally what you can do to help meteorologists make better forecasts. For more details, click on over to the FB event page that the folks at the Freeport Library created. I hope to see you there!

-Jack

Heavy Rain Possible This Weekend Following Oppressive Heat Tomorrow

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Hello everyone

Current Conditions This Afternoon (4:30 PM) Verifying Today's Forecast
Current Conditions This Afternoon (4:30 PM) Verifying Today’s Forecast

This morning’s showers are now well offshore as an upper level disturbance rotates eastward. Looking at the forecast verification, temps worked out fairly well with widespread 70’s under cloudy skies. Some 80’s were reported in SW NH as expected. I didn’t think clouds would clear out enough in the far north for 80’s but by the looks of obs across SE Quebec, some warmer temps likely found their way into those areas. This morning’s showers evolved as forecast but so far no storms have been reported in NE areas though some leftover convection from Quebec could still find its way in later this evening. Overall, today was a pretty good forecast.

4km NAM Showing Oppressive Dew Points Tomorrow. Image Credit: Weatherbell
4km NAM Showing Oppressive Dew Points Tomorrow. Image Credit: Weatherbell

Tomorrow will begin a two-day sufferfest as we sit to the south of a frontal boundary. Look for highs to climb into the low to mid 90’s for most SW areas with upper 80’s elsewhere. SW winds will keep any sea breeze attempts at bay. Humidity will be the big story with dew points rising into the low 70’s for most with some upper 60’s north and east. The heat and humidity will combine to offer up heat index values near or over 100. Heat advisories are up for SW NH and York County ME due to this dangerous heat.

12Z 4km NAM Showing Widely Scattered Showers Possible Tomorrow. Image Credit: Weatherbell
12Z 4km NAM Showing Widely Scattered Showers Possible Tomorrow. Image Credit: Weatherbell

While there is no organized trigger for showers or storms tomorrow, there will be plenty of moisture around and as a result, even the differences in heating of the mountains could be enough to trigger a spot shower or two tomorrow afternoon. Again, this does not look widespread by any means but don’t be surprised to see a few drops if you’re out and about in the mountains. Most of the area looks to bake under the hot sun with no relief from clouds or precip.

12Z 4km NAM Showing More Dangerous Heat Friday. Image Credit: Weatherbell
12Z 4km NAM Showing More Dangerous Heat Friday. Image Credit: Weatherbell

More dangerous heat is on tap for Friday as we continue to sit south of the front. Temps are likely to be only slightly cooler than Thursday but dew points are likely to soar even higher. Temps in the low to mid 90’s combined with dew points in the 70’s will result in heat indexes exceeding 100 for much of the SW portion of the area. This is astronomical for Northern New England and nothing to take lightly. Be sure to take proper precautions such as hydration and limiting outside activity during the hottest part of the day. By evening, storms will be rumbling into the area from the NW and will begin to bring relief along with heavy rain, gusty winds, and frequent lightning.

12Z GFS Showing Sufficient Shear For Severe Storms Friday. Image Credit: Accuweather
12Z GFS Showing Sufficient Shear For Severe Storms Friday. Image Credit: Accuweather

The hot temps and oppressive humidity will result in a very unstable atmosphere Friday. Remember the three severe weather ingredients? We will have plenty of fuel. The approaching cold front will be our trigger and indications are that there will be more than enough shear to organize storms. This means that there is a threat for severe storms tomorrow with gusty winds being the main threat. This threat is greatest in the mountains where the front will be closer during peak daytime heating.

Current Water Vapor Satellite Showing All The Players For The Weekend Rain Event. Image Credit: COD Nexlab
Current Water Vapor Satellite Showing All The Players For The Weekend Rain Event. Image Credit: COD Nexlab

The pattern change I’ve been talking about for almost a week is finally here. A strong area of high pressure is setting up over the Western Atlantic as a trough is digging into the Western US. The SW flow on the periphery of the high and on the eastern side of the trough is directing a pool of tropical moisture associated with the tropical disturbance over Florida our way. Meanwhile, a powerful storm over Hudson Bay is pushing a cold front SE. Energy will eject from the Western trough and move east combining with the front and the moisture to bring rounds of showers and storms beginning Friday evening and wrapping up Monday.

12Z GFS Showing The Pattern For The Weekend
12Z GFS Showing The Pattern For The Weekend

I show the GFS 500mb vorticity (energy) and SLP map as it gives a general overview of what the pattern will be like from Friday evening through Monday morning. A front will be stalled overhead with several disturbances aloft and waves of low pressure at the surface promoting heavy rainfall. A final upper level disturbance and associated surface low will move east Monday bringing a final round of heavy rain. The exact location of this rain is still a bit up in the air. Some guidance suggests it will be right over us while some suggest we only see the far northern fringes of it. Those details should come into more clarity as that part of the event draws closer.

12Z GFS Showing The Moisture Plume Being Forced Offshore Monday
12Z GFS Showing The Moisture Plume Being Forced Offshore Monday

The front will continue to provide the focus for showers Sunday before the whole Western trough swings through with one final round of heavy rain Sunday night into Monday morning. This round is the most uncertain as there are some indications that it will primarily impact Southern New England leaving us dry. After this round passes out to sea, either via us or SNE, drier air looks to move in for the beginning of next week.

12Z GFS With This Week's Overview
12Z GFS With This Week’s Overview

The trend for this week will be a stifling start tomorrow and Friday before clouds and showers bring gradual cooling through the beginning of next week. Rounds of showers and storms could be heavy at times with flash flooding possible. Each round of rain will remove some moisture from the atmosphere so that by the beginning of next week we are left with a fairly dry and comfortable airmass. The pattern supports more rain by the middle or latter part of next week but there are no significant signals for a specific event yet.

I will have another update tomorrow morning. As a reminder, I will be gone from Friday afternoon through Sunday afternoon. I will post Friday morning but not again until Monday morning (there is the low potential I will return in time for a post Sunday evening but alas that depends on the weather). During this time, please revert to your primary source for weather information, such as the NWS or local media.

-Jack

 

 

Thunderstorms And Heavy Rain As We Head Into The Weekend

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Hello everyone!

We have two interesting weather systems coming our way in the next few days. The first will be a cold front dropping south out of Canada tomorrow afternoon. It will bring with it the threat for showers and storms tomorrow afternoon and into the evening. No severe weather is expected. That front will lose steam and stall somewhere just to our south Friday morning at which point a wave of low pressure will try to develop and move NE along the front. Where that low tracks and how strong it is will determine the outcome of our second weather event and how much beneficial rain we receive. Quieter weather is expected to follow that event with mild temps and sunny skies expected into next week.

Thursday Storms

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12Z GFS Showing Some Instability Present Tomorrow Afternoon. Image Credit: Weatherbell

Let’s do a quick rundown of the three ingredients needed for strong/severe storms. Doing this will explain why some storms are likely but also why severe storms are not. Instability is a go as temps soar into the 80’s and low 90’s while dew points climb as well, into the upper 60’s to low 70’s. Nothing incredible, but certainly enough for some booms.

12Z NAM And GFS Both Showing Upper Level Energy And A Surface Cold Front To Trigger Storms.
12Z NAM And GFS Both Showing Upper Level Energy And A Surface Cold Front To Trigger Storms.

How about a trigger? An upper level disturbance will be pinwheeling around the base of an upper low over Eastern Canada tomorrow. Meanwhile, a surface cold front will be sagging south across the region tomorrow. Both of these are shown in the image above with the left two panels representing one model forecast and the left two representing another. While there are some differences, the general idea remains the same. The general idea is that there will be enough of a trigger to get at least a few storms going. The big question then becomes, will they become organized enough to produce severe weather?

12Z NAM Showing Very Little Shear To Organize Storms. Image Credit: Accuweather
12Z NAM Showing Very Little Shear To Organize Storms. Image Credit: Accuweather

The short answer to that question is no. While guidance indicates some marginal shear, perhaps enough to trigger an isolated severe storm, there is not enough shear to support widespread severe weather. This means that you can expect your typical garden variety thunderstorms tomorrow with heavy rain, frequent lightning, and possibly some gusty winds. Remember, storms don’t have to be severe to be dangerous. Lightning can strike up to 15 miles from a storm and is just as dangerous as strong winds or large hail. When thunder roars, go indoors.

12Z 4kNAM Showing Scattered Storms Tomorrow Afternoon. Image Credit: Weatherbell
12Z 4kNAM Showing Scattered Storms Tomorrow Afternoon. Image Credit: Weatherbell

Putting that all together, here’s the big picture for tomorrow afternoon/evening. Scattered storms look to develop in the early afternoon over the mountains and will slowly move SE through the afternoon and into the evening hours before reaching the coast in a weakened state later in the evening. Storms are most likely in the mountains and least likely along the coast and especially along the midcoast.

Friday Rain

12Z GFS Showing The Setup Leading To Possible Rain Friday. Image Credit: Weatherbell
12Z GFS Showing The Setup Leading To Possible Rain Friday. Image Credit: Weatherbell

Tomorrow’s cold front will stall just off the coast Friday morning and a low pressure area will develop along its southern end over the Mid Atlantic states. The GFS shows this situation well with the map shown depicting conditions at 8:00 Friday morning. Scattered showers are possible during this time but steady rain, if it happens, is likely to occur Friday afternoon/evening. There is still quite a bit of uncertainty in the forecast for Friday as guidance offers several different possibilities. There are two scenarios, the dry scenario, and the wet scenario. I break each down below along with which I think is more likely.

A Comparison Of The 12Z NAM (Right Panels, Wet Solution) And The 12Z GFS (Left Panels, Dry Solution).
A Comparison Of The 12Z NAM (Right Panels, Wet Solution) And The 12Z GFS (Left Panels, Dry Solution). Click To Enlarge.

The NAM and GFS models from this afternoon present the two more extreme solutions: almost no rain on the GFS and tons of rain on the NAM. The map above is data-rich and small, so click it to enlarge it so you can see all the details, if you want. The main difference between the models revolves around the amount of upper level energy in the atmosphere and where that energy is located. The NAM has way more energy (lots of red, top right panel) while the GFS has very little (thin stripe of red, top left panel). Also of note is the location of the kicker disturbance. The software I use to get the data for these graphics makes any boundaries very hard to see so I highlighted New England as well as the Quebec/Ontario border to show the differences in location of the kicker disturbance. Notice that the NAM has it farther west, closer to the border while the GFS has it well east of the border. Keep in mind these maps are valid at the same time. By keeping the kicker farther west, the NAM allows for more moisture to stream northward and also gives the low more time to strengthen, bringing more rain. The GFS on the other hand hurries the kicker along, pushing the storm and the moisture offshore quickly.

12Z NAM (Right) vs 12Z GFS (Left) Both Showing Available Moisture (PWAT)
12Z NAM (Right) vs 12Z GFS (Left) Both Showing Available Moisture (PWAT)

The difference in moisture can be seen in the Precipitable Water maps which show how much moisture is available. Notice how the blue (super moisture laden air) is much more abundant and closer to the coast on the NAM (right) compared to the GFS (left). Also notice that on both models, SE MA gets in on the action. Heavy rain is likely there but rain chances become more uncertain as you head NW. Notice also how the mountains are in fairly dry air (brown/yellow). Very little rain is expected there. The battleground so to speak will be those areas in between the SE MA coast and the ME/NH mountains.

Current (12Z Today) Upper Air (500mb) Analysis. Image Credit: Meteocentre
Current (12Z Today) Upper Air (500mb) Analysis. Image Credit: Meteocentre

What do I think will happen? Right now I am leaning towards the GFS’s scenario because the larger scale pattern supports it. This morning’s upper air map shows this well. Winds in the upper atmosphere are overwhelmingly west-east over North America with only shallow ridges and troughs. This “zonal” pattern does not lend itself to troughs digging and amplifying which is what the NAM depicts. Right now, the WNW flow around the heat dome over the SW US looks likely to simply shove the fledgling low off the coast, leaving us with just a few showers or perhaps a brief period of steady rain. SE MA is likely to see the steadiest and heaviest rain with showers making their way all the way up to the base of the mountains. The mountains are likely to stay mostly dry as they are simply too far removed from the deep moisture to our SE. I’ll have more on this tomorrow along with updates on the thunderstorm threat.

Quieter weather is expected through much of next week.

-Jack

Cool And Unsettled This Week

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Hello everyone!

As one light snow event races off towards Newfoundland, another waits on our doorstep for tomorrow. Following light snow tomorrow, temps stay cool into Wednesday before warming up ahead of a more significant storm Thursday into Friday. This one should be mainly rain but quite a lot of it is expected. That storm departs Friday night leaving afternoon showers and thunderstorms around for the weekend as we sit under an upper low.

Overview: This Week’s Weather At A Glance

12Z GFS Giving An Overview Of The Week Ahead.
12Z GFS Giving An Overview Of The Week Ahead.

Here’s this week’s weather at a glance for those who just want the short version. I hate to say it, but there are no long term warm ups in the forecast and even the mid/late week warm spell will struggle to top out above 50F. April in Maine is cruel. Details on our two incoming storms are below.

The Setup: Tomorrow’s Snow

12Z RGEM Showing The Setup Tomorrow Morning With Light Snow. Image Credit: Weatherbell
12Z RGEM Showing The Setup Tomorrow Morning With Light Snow. Image Credit: Weatherbell

Low pressure is currently diving SE across the Great Lakes and will be making its way to SNE by tomorrow morning. It will be too far south for significant impacts here in ME but points south could see several inches. Snow will move in around daybreak and move out in the evening. It will be light and accumulations will be similarly unobtrusive. Because this system is much weaker than the one today, no crazy winds are expected.

Tomorrow’s Snow: Weak Upper Support Means Weak Storm

Afternoon Upper Air Analysis Showing Little Support For Tomorrow's Storm. Image Credit: SPC Mesoanalysis
Afternoon Upper Air Analysis Showing Little Support For Tomorrow’s Storm. Image Credit: SPC Mesoanalysis

The reason this storm will remain weak and to the south is that above 15,000 or so feet, the storm doesn’t exist. In the image to the right you can see the upper level footprint of our storm today with very strong winds and a big dip. Tomorrow’s storm? It’s circled in red. If you can see any significant storm there, let me know because I’m having a hard time. The lack of significant upper level support means this one won’t have a chance to intensify or turn NE when it reaches the coast. The net result? Very little snow for ME and NH.

The Setup: Late Week Heavy Rain

12Z GFS Showing The Upper Air Setup For The Late Week Rain. Image Credit: Accuweather
12Z GFS Showing The Upper Air Setup For The Late Week Rain. Image Credit: Accuweather

Our next storm arrives late week with heavy rain likely. Notice the NW/SE orientation of the longwave features. This means that the trough to our west will be feeding tropical air northward into our area on strong S/SE winds. Those S/SE winds also mean that storms will be more likely to move up the coast when they develop as the individual shortwaves rounding the base of the trough. The end result? Heavy rain is likely at some point between Thursday and Friday. Exactly when and exactly how much rain falls has yet to be determined.

Late Week Heavy Rain: The Tropical Connection

12Z GFS Showing The Tropical Connection Available Late Week
12Z GFS Showing The Tropical Connection Available Late Week

When the rain does come, it will bring with it air straight from the tropics as the 12Z GFS PWAT map shows. This helps to establish fairly high confidence we will see heavy rain at some point late this week. The greatest threat for heavy rain will be Thursday night but it could fall any time Thursday or Friday. Guidance is indicating fairly significant rain could fall with amounts likely in the 1-3″ range. This could cause some rapid stream rises so be aware of that potential. Despite that, no widespread flooding issues are expected.

Next Weekend: The Return Of The Cold

12Z GFS Showing An Upper Low Lingering Over The Area Next Weekend. Image Credit: Accuweather
12Z GFS Showing An Upper Low Lingering Over The Area Next Weekend. Image Credit: Accuweather

Looking ahead to next weekend, the upper level low that brought the heavy rain Thursday/Friday will park over our area bringing cool and unsettled conditions. Expect temps to again drop back towards freezing with rain/snow showers possible. No accumulations or organized storm systems are on the horizon but showers driven by daytime heating will likely become a fact of life heading into the second week of April.

I’ll have more updates through the week.

-Jack

From Winter To Spring This Week

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Hello everyone!

The weather over the coming week will be a period of transition from the bitter winds and snows of winter to the warm winds and heavy rains of spring. After you finish complaining about the wintry start to the week, remember that parts of MA and CT are seeing 3-6″ of snow driven by 60-70 mph winds and accompanied by crashing thunder. We’re being cheated out of a fascinating event.

The Setup: This Evening

Evening Water Vapor Satellite Showing The Development Of A Strong And Dynamic Clipper Tonight/Tomorrow Morning. Image Credit: COD
Evening Water Vapor Satellite Showing The Development Of A Strong And Dynamic Clipper Tonight/Tomorrow Morning. Image Credit: COD

An extremely potent disturbance is currently blasting SE across the Eastern Great Lakes. The impressive couplet of strong rising/sinking air indicates this is an extremely strong disturbance. Arctic air is already pouring in behind this storm with winds across the Midwest gusting over 50mph this afternoon. This whole system is moving east quite quickly and will be in New England tomorrow morning. Also going on this evening is the development of an offshore wave embedded in the subtropical moisture feed. This will drag the moisture offshore which is why the arctic disturbance won’t bring us a blockbuster storm.

Light Snow: Tomorrow Morning

12Z RGEM Showing The Setup Tomorrow Morning. We're On The Edge Of This One. Image Credit: Weatherbell
12Z RGEM Showing The Setup Tomorrow Morning. We’re On The Edge Of This One. Image Credit: Weatherbell

The RGEM model is showing what the storm will look like when it’s over our area tomorrow at 8 AM. Most southern areas will see at least a few flakes and York County could see a couple inches. Most just get a dusting if that. The mountains look to remain completely dry. The bulk of this one will be in Southern New England where the higher elevations of eastern CT and MA will see up to 6″ of snow, hurricane force wind gusts, and thundersnow. For those areas, this will be a pretty crazy storm. For everyone, the storm moves quite quickly and is gone by tomorrow afternoon.

High Winds: Tomorrow All Day

12Z GFS Showing Wind Potential Tomorrow.
12Z GFS Showing Wind Potential Tomorrow.

One impact that the mountains and the coast alike will feel will be the winds. Winds under the yellow line are eligible to take a hike to the surface. It is hard to see here but the GFS does have a 50kt contour in the blue circled area Sunday morning for Portland. A good rule of thumb I learned from CBS 13 meteorologist Charlie Lopresti is to take whatever the model puts out for knots in the mixing layer and forecast the same value in mph. That would give us 50mph wind gusts tomorrow morning which seems reasonable based on the strength of the storm. The NWS has issued a Wind Advisory for tomorrow and scattered power outages are certainly possible. Winds subside tomorrow evening.

Bitter Cold: Tomorrow Through Tuesday

18Z NAM Showing Temps Barely Getting To Freezing Monday. Image Credit: Weatherbell
18Z NAM Showing Temps Barely Getting To Freezing Monday. Image Credit: Weatherbell

The core of the Arctic airmass moves overhead Monday and the chill will definitely be felt across the area. Temps look to barely get to freezing (if that) even under the powerful April sun. Despite the bitter cold temps, winds will subside and thus temps may even feel warmer when compared to the bitter winds of Sunday. Temps won’t be going very far up on Tuesday either and it’s not until Thursday that temps get even back to normal which is around 50.

The Setup: Tomorrow Evening

12Z GFS Showing The Upper Level Setup Monday Night Ahead Of Our Next Snow Event. Image Credit: Accuweather
12Z GFS Showing The Upper Level Setup Monday Night Ahead Of Our Next Snow Event. Image Credit: Accuweather

By tomorrow night, our next clipper will be approaching from the west bringing another chance for snow. This is the upper air pattern for the wee hours of Monday morning showing an unfavorable setup for snow. The two disturbances are separate and fairly weak. However, the trough is tilting slightly negative (NW to SE) at the last minute. This is why I think we at least see a little snow out of this storm. The seeds for the return of Spring can be seen across MT. That storm arrives Thursday into Friday.

More Light Snow; Monday

12Z GFS Showing The Likely Impacts For The Monday Storm. Image Credit: Accuweather.
12Z GFS Showing The Likely Impacts For The Monday Storm. Image Credit: Accuweather

The snow from this storm should reach slightly farther north compared to tomorrow’s flakes. Flurries should make it north to around Route 2 or maybe a little north of there. Jackman and points north likely miss out again. The coast and inland points south of Portland likely see steadier snow that adds up to an inch or two. The heavier precip is again to our south over MA and CT where several inches of snow are possible. The main difference compared to Sunday will be the lack of intense winds though there will be some light NE breezes.

The Setup: Late Week

12Z GFS Showing The Setup For The End Of The Week's Return To Spring. Image Credit: Accuweather
12Z GFS Showing The Setup For The End Of The Week’s Return To Spring. Image Credit: Accuweather

By the end of the week, the pattern will have shifted slightly. Weather features in the mid latitudes (us) can be classified into two basic categories: longwave features and shortwave features. The long wave features can often be picked up by models many days out. The development of a longwave trough would lead to a colder/stormier pattern. Shortwaves are responsible for the individual storms that actually drop the rain/snow. These features are not often resolved well on models many days out hence forecast uncertainty in specific impacts. The longwave pattern for the end of the week features a Western ridge and an Eastern trough, both oriented NW to SE (negatively tilted). The longwave trough in the east is situated to our west which will lead to the development of southerly flow aloft.

The Return Of Spring: Heavy Rain Possible Late Week

12Z GEM Showing Heavy Rain Potential Late Week. Image Credit: Weatherbell
12Z GEM Showing Heavy Rain Potential Late Week. Image Credit: Weatherbell

This will bring in a feed of tropical moisture into the area. However, it’s up to the individual shortwaves to put the tropical moisture and thus the heavy rain onto a precise location. Where this is remains up for debate. Anywhere in New England including Maine is in play. Should the storm shift farther east, we may be dealing with a snow event. Should it shift farther west, NY would get the heavy rain while a warm and sticky airmass settles into our area.

I’ll have more details on this storm as we get closer. It looks like the track schedule will allow for evening updates this week. We’ll see how that goes, it’s about as unpredictable as the forecast.

-Jack

More Messy Weather Tomorrow Into Friday

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Hello everyone!

Early spring is in full swing in Maine and this week will be a good reminder that Spring is a battle between warm and cold. In the beginning, cold wins. Slowly but steadily, the warm air wins out but it will take many messy battles before that happens. For now, the advantage is with the cold. We’ll see that in full swing in the next few days as a powerful Colorado low which is currently bringing every type of weather under the sun from Colorado/Nebraska blizzards to Texas tornadoes. The storm will be significantly weaker by the time it gets to us but will still be potent enough to cause some issues tomorrow into Friday.

The Setup: This Evening

Afternoon Observations Showing Our Next Storm Setting Up To Our West. Image Credit: COD
Afternoon Observations Showing Our Next Storm Setting Up To Our West. Image Credit: COD

A cold front is moving through the area currently (blue line on map) and winds behind it are out of the north which is bringing in cold air. Canadian high pressure is diving SE across Eastern Canada and will continue to supply this cold air through most of the event. Low pressure is moving across the Western plains and will be moving NE towards our area tonight into tomorrow. A warm front extends out ahead of this storm and is linked to the cold front bringing us the cold air this evening. This warm front will try to push north tomorrow and Friday but cold, dry air in place will impede its progress significantly.

Round One: Snow Tonight Into Tomorrow Morning

HRRR Showing Snow Moving In Tomorrow Morning Well Ahead Of The Main Storm. Credit: Weatherbell
HRRR Showing Snow Moving In Tomorrow Morning Well Ahead Of The Main Storm. Credit: Weatherbell

Precip starts late tonight and tomorrow morning in the form of snowfall. Initially, everyone is snow and very light accumulations are likely for everyone by the morning commute. Snow will be light though and major issues are not expected. That tapers off tomorrow morning leaving mid-day tomorrow mainly dry but cool. The main system can be seen at the very end of the loop spreading into western PA/NY.

Round Two: Main Storm: Surface Edition Friday

12Z HRDPS Showing Winds Friday Morning At The Surface. Notice The Warm Winds At The Coast And The Cold High Pressure (No Winds) Holding Strong Inland. Image Credit: Weatherbell
12Z HRDPS Showing Winds Friday Morning At The Surface. Notice The Warm Winds At The Coast And The Cold High Pressure (No Winds) Holding Strong Inland. Image Credit: Weatherbell

The warm front mentioned in the setup section will attempt to move north overnight tomorrow into Friday. It will hit a brick wall at around route 1 which will let temps rise above freezing at the immediate coastline but will keep inland areas below freezing. This pattern should continue through mid afternoon Friday before the low passes overhead and the trailing cold front busts up the inversions holding the low level cold in place. This is the surface pattern that is known far and wide for not changing. Guidance says most of the region goes over to rain by 9 AM. I think it will be 3 or 4 in the afternoon before temps rise above freezing in inland/mountain areas.

Round Two: Main Storm: Upper Air Edition Friday

12Z NAM Showing The Upper Air Setup Friday Morning Over Lewiston.
12Z NAM Showing The Upper Air Setup Friday Morning Over Lewiston.

Aloft, a much different story will play out. There is no Canadian high above 3-4 thousand feet. Therefore, there is no source of cold air. Warm air blasting north will have no trouble pushing the cold air in place out of the way. This will result in a classic mixed precip setup where snow forms in the cold layer really high up before melting in the warm mid levels of the atmosphere. It then refreezes close to the surface resulting in sleet and freezing rain depending on the depth of the cold at the surface. With the cold Canadian high just to our north, there will be a continuous feed of cold dry air being funneled down the east side of the mountains. This is a classic Cold Air Damming setup and CAD always lasts longer than you think even if you think it will last longer than you think. That tongue twister boils down to the fact that cold air moves when it’s good and ready too and it’s not usually to motivated to go anywhere.

Round Two: Main Storm: Impact Map Friday

Expected Impacts From This Storm
Expected Impacts From This Storm

Following the initial snow tomorrow morning, this is what I expect for impacts. Everyone starts out with a little mix but strong SE winds should quickly warm the coast up above freezing resulting in mainly rain there. Despite that, do be prepared for slick conditions everywhere as sleet and freezing rain are a dangerous combo especially with some leftover snow around. Inland, even a few miles, cold air will put up a much mightier fight. Look for snow changing to sleet changing to freezing rain. Sleet and freezing rain look to be the dominant precip types through this event. Snow will quickly change over to a mix as warm air blasts in unimpeded aloft but for most areas away from the coast, the surface high will be enough to keep temps below freezing at the surface for a good long time. In terms of accumulation, in the green area, a trace to a tenth of an inch of ice is expected. In the pink area, a tenth to a quarter inch of ice is expected.

Rounds One And Two Combined Snowfall: Tonight Through Friday

Expected Snowfall Before The Change To Mix/Rain
Expected Snowfall Before The Change To Mix/Rain

Here is what I expect for snowfall before we change to a mix or rain depending on location. While I have the Penobscot Bay and York County regions missing out on any accumulations, I wouldn’t be overly surprised to see coatings there tomorrow morning. This all basically is gone Friday afternoon as sleet and freezing rain turn the ground into an icy crust. The March sun angle is still a factor here despite cloudy conditions and sleet/freezing rain could have a hard time accumulating on pavement. However, please use caution especially Friday as any untreated roads will likely be slick. This snowfall map includes precip tonight and into tomorrow morning.

Round Three: Possible Storm: Early Next Week

12Z GEFS Ensembles Showing The Potential For More Stormy Weather Early Next Week. Image Credit: Weatherbell
12Z GEFS Ensembles Showing The Potential For More Stormy Weather Early Next Week. Image Credit: Weatherbell

Following this storm, we have a nice early Spring weekend to look forward too with cool temps and sunny skies. However, tranquil patterns rarely last long in March in Maine and by early next week, another storm threatens. As you can see here, guidance is converging on the idea we see some sort of precip. How much/what type is still yet to be determined. Snow, mixed precip, and rain are all on the table as well as no storm at all though that is becoming less likely. While it is too early to offer details, I just wanted to put that out there as something to watch in the coming days.

-Jack