Tag Archives: winter

Messy Winter Storm Monday Night Into Tuesday

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

Winter’s Comeback Begins

Hello everyone!

I hope all you worshipers of warmth enjoyed your brief break, because winter’s comeback is beginning. Rain and snow will arrive tomorrow evening becoming mostly snow during the overnight hours. Snow will last through the mid morning hours before tapering off to flurries/drizzle by Wednesday afternoon. After that, an active pattern looks to kick into gear with a possibly significant precipitation event by the end of the week.

WV Satellite Imagery Showing Our Storm System Off To The West. Image Credit: COD
WV Satellite Imagery Showing Our Storm System Off To The West. Image Credit: COD

The setup for this event involves almost everything you can see on the map here. Cold air is moving SE into the area as a backdoor cold front moves through tonight. Our storm is located all the way back in Kansas and will weaken as it moves NE. The moisture pipeline will be in business from the Gulf of Mexico but it will be weakening along with the storm. The bottom line: with all the elements weakening as they approach us and the pattern across the Northern Hemisphere generally being flat/zonal, this won’t be an event that features heavy precip. Let’s look at some of the dynamics associated with the system to test that hypothesis.

12Z GFS Showing The Weak Upper Level Dynamics Early Wednesday Morning. Image Credit: Accuweather
12Z GFS Showing The Weak Upper Level Dynamics Early Wednesday Morning. Image Credit: Accuweather

The pattern aloft can give many clues as to how storms will behave at the surface and this time is no different. For big storms, we want our upper level energy to be strong, negatively tilted, and consolidated. This situation will feature the exact opposite of that as our energy is weak, strung out, and positively tilted. Even though a coastal low will develop, it will move east then south-east rather than north-east up the coast. You can thank the positive tilt for that. The two disturbances are separate and the lack of strength can be attributed to this.

Upward Motion Map Showing Broad/Weak Lift Wednesday Morning. Image Credit: Accuweather
Upward Motion Map Showing Broad/Weak Lift Wednesday Morning. Image Credit: Accuweather

Sure enough, our hypothesis of weak lift/precip holds up in the upward motion department as the 12Z NAM shows. Notice how we enjoy the yellows/oranges rather than the reds/pinks that usually show up on maps like this during big storms. As a result of the weakening surface storm, the disorganized upper level dynamics, and the weak lift, precip will be light to moderate at best and heavy bands are not expected.

12Z NAM Vertical Profile Giving An Overview Of The Event.
12Z NAM Vertical Profile Giving An Overview Of The Event.

Here’s the NAM’s take on the event shown through a vertical cross-section of the atmosphere above Portland through time. While the NAM certainly has its flaws, it gives a good look at the various dynamics involved through the event. Notice how the moisture near the surface remains even well after the snow may stop. Given the colder air moving S behind the departing low and the presence of this moisture, look for freezing drizzle to be an issue through the day on Wednesday. This will result in slick roads even after the snow moves out.

12Z NAM Showing Precip Moving In Tomorrow Evening. Credit: Tropical Tidbits
12Z NAM Showing Precip Moving In Tomorrow Evening. Credit: Tropical Tidbits

Precip will arrive tomorrow evening in the form of snow inland and a rain/snow mix along the immediate coast. Everyone except the extreme SE midcoast (Rockland) and coastal York County will quickly go over to snow which will be the dominant precip type throughout the event. As coastal low pressure develops off Long Island, expect precip to become focused in the southern half of the area by Wednesday morning before tapering off to flurries and freezing drizzle by Wednesday afternoon. A weak inverted trough will act to keep the moisture around for that freezing drizzle even well after the snow departs.

Expected Snowfall Tuesday Night Through Wednesday Morning
Expected Snowfall Tuesday Night Through Wednesday Morning

Here’s what I think everyone will end up with when all is said and done on Wednesday afternoon. The coast sees the least due to mixing and totals drop off to the NE as less precip will fall there. The Jackpot will be in NH and far W ME where 6-8″ are possible in the foothills and mountains. This will be a great refresh for the ski areas especially those in the whites and places in Maine like Sunday River, Shawnee Peak, and Mt Abram. Farther NE, Sugarloaf will definitely get some flakes but won’t have the lift to squeeze out more than 2 or 3″. I’ll see if I have time to update this tomorrow before the flakes fly.

12Z GEM Showing More Flakes For Some On Thursday. Image Credit: Weatherbell
12Z GEM Showing More Flakes For Some On Thursday. Image Credit: Weatherbell

More flakes will be in the air on Thursday as a cold front/weak storm drifts by to our north. The mountains and far north will see the most out of this one with a whopping 1″ possible. Some upslope areas might see 2″ but that’s about it. Farther south, flurries can be expected across the foothills and coastal plain while the shorelines and southern NH may not see anything at all. The timeframe for this is during the day on Thursday.

12Z GFS Showing More Light Rain/Snow Showers Saturday. Credit: Weatherbell
12Z GFS Showing More Light Rain/Snow Showers Saturday. Credit: Weatherbell

Our pattern of many weak little events will continue Saturday with the arrival of cooler air accompanied by rain and snow showers. At the moment, accumulations look to be less than an inch away from the coast but the cold air is important because it will set the stage for the next event which will arrive sometime this coming weekend or early next week. Whatever that event may be, it will likely bust up our ‘halftime’ pattern, ushering in colder and stormier weather to finish January and begin February.

12Z GEFS Ensembles Showing Rumblings Of Action Early Next Week. Any Specifics Remain Incredibly Uncertain. Image Credit: Weatherbell
12Z GEFS Ensembles Showing Rumblings Of Action Early Next Week. Any Specifics Remain Incredibly Uncertain. Image Credit: Weatherbell

Here is a quick look at the potential storm system early next week (about 7-8 days from now). As with any potential system that far out, the details are up in the air but ensemble guidance is supported by the large-scale pattern in suggesting some sort of system could be brewing around then. I’ll have more as we get closer if it continues to look like an impactful storm is a possibility.

GEFS 10mb Temperature Anomaly Maps Show Changes In The Stratosphere Over The Next 7-10 Days. Image Credit: Weatherbell
GEFS 10mb Temperature Anomaly Maps Show Changes In The Stratosphere Over The Next 7-10 Days. Image Credit: Weatherbell

Now I’ll take a minute to look forward at the pattern for the next couple weeks. Winter is coming back and the change is beginning at the very top of the atmosphere right now. Temperatures in the stratosphere over the North Atlantic have warmed dozens of degrees Celsius in just a few days and this will be a killer blow to the stratospheric polar vortex (the real one, not the fake one the TV stations make up for ratings/clicks/likes/shares etc). By the time we get to the middle of next week, the vortex (light blue) will be considerably weaker than it is now as multiple Sudden Stratospheric Warming events occur (red circles).

The weaker polar vortex will allow cold air to spill southward resulting in a return to winter for Maine and New Hampshire. These changes to the pattern are beginning now and will likely begin to influence our pattern by the time that storm early next week arrives in one form or another. In short, the comeback is coming.

More this week if I have time between school work, track, and sleep.

-Jack

Coastal Storm To Bring Light Snow To The Coast This Evening

Hello everyone!

I was hoping to get an update on this evening’s system out last night but other commitments prevented that so here’s a quick rundown of my thinking and why we’re not going to see a significant event.

12Z Weather Balloon Data Showing Very Dry Air In Place. Image Credit: SPC
12Z Weather Balloon Data Showing Very Dry Air In Place. Image Credit: SPC

One inhibitor of large snowfall accumulations will be ample dry air ahead of the storm that will evaporate some of the snow before it can reach the ground. A good inch or two worth of snow could be lost to mid level dry air. Do notice though that the entire atmosphere is plenty cold enough for snow. There is zero threat of any mixing with this storm but there are plenty of other forecast challenges to make things interesting!

10 AM 500mb Winds. Image Credit: Nullschool
10 AM 500mb Winds. Image Credit: Nullschool

Looking at the mid levels, it is fairly easy to see why we’re not in for a big storm and why the highest snowfall amounts will be along the coast. Both disturbances associated with the storm are positively tilted and separate while winds ahead of the system are out of the WSW which pushes the storm ENE. There is some respectable divergence (winds blowing away from each other) over the system but the setup lacks the explosive dynamics needed for a stronger storm that tracks farther west. Development of these dynamics will occur eventually but too late for us. Drive to New Brunswick or Nova Scotia for those.

10 AM Upper Level Wind Map. Image Credit: SPC
10 AM Upper Level Wind Map. Image Credit: SPC

Upper level dynamics are similar to the mid level dynamics: modestly favorable but not explosive. The storm is in the right entrance region of a very strong but low amplitude jet streak. There is only one jet and no jet coupling meaning that we lack the explosive dynamics needed for a strong storm. This is the same story across all levels of the atmosphere and explains why we’re not in for any big snow. However, that doesn’t mean some areas won’t get a moderate storm.

10 AM 700mb Analysis. Image Credit: SPC
10 AM 700mb Analysis. Image Credit: SPC

A look towards the mid levels shows pretty much the same story with one exception. Notice all the WSW flow and the positively tilted troughs but also notice the kink in the flow right over the storm itself. This kink will gradually sharpen and develop along with SE winds ahead of it. The timely development of these SE winds will be crucial to pulling the deeper moisture NW towards our area. If the kink intensifies more quickly, the SE winds will as well, and the moisture will be able to move NW therefore giving us more snow. If the kink lags in development, the opposite will be true.

Kachelmann Swiss Model Showing Expected Impacts This Evening. Image Credit: Kachelmann
Kachelmann Swiss Model Showing Expected Impacts This Evening. Image Credit: Kachelmann

Now that we’ve dug into all the dynamics behind this storm and what some of them mean, we can focus on impacts. This map from the Kachelmann Swiss model shows how the coast will see the moderate snow, the foothills the lighter snow, and the mountains only flurries. Also notice the bands of ocean enhanced snowfall across eastern MA as Arctic air currently over ME is drawn across the warm Gulf of Maine waters on NE winds ahead of the storm. In those heavy bands, over a foot of snow is possible along with blizzard conditions. This will be limited to eastern/coastal MA and no impacts that significant are forecast for the ME or NH coastlines.

HRRR Showing How Snow Evolves Over The Next 18 Hours. Credit: Weatherbell
HRRR Showing How Snow Evolves Over The Next 18 Hours. Credit: Weatherbell

Snow will arrive in the next hour across southern NH and will be falling across the ME coast by sundown this evening. Notice how the mountains see hardly anything while the coast enjoys moderate snowfall. Also check out all the ocean enhancement as bitterly cold air gets drawn into the storm and passes over the warm Gulf of Maine. The snow will move out in the predawn hours as the storm moves farther offshore.

Expected Snowfall Through Tomorrow Morning
Expected Snowfall Through Tomorrow Morning

Here’s my snowfall forecast for tomorrow. This will be a light/fluffy snow that will be easy to move, both by human and by wind. With steady northerly winds, some blowing snow is certainly possible which could create lower visibilities and some drifting in exposed areas though nothing major is expected.

Another cold few days are in store before a brief warmup mid week as low pressure passes to the west.

-Jack

 

Major Winter Storm Tomorrow Night

Hello everyone!

A very interesting and exciting ~18 hours is in store from tomorrow evening through early Friday morning. During this time, look for torrential downpours along the coast, whiteout snows inland, and strong gusty winds for all. This will be brought to you by a rapidly intensifying coastal storm that will deepen roughly 20mb in 12 hours. This is double the rate of deepening needed for official bombogenesis!

Just a quick note before the fun… If you’ve been reading my storm updates for a while, you know I get into some fairly high level (and interesting!) meteorology while outlining what I expect to happen. If you’re new to my blog, this is how I like to operate as I think it gives you the reader a unique look “under the hood” of weather forecasting. I try to explain technical concepts in an accessible way so you too can become part weather geek. If you’re not into the “why behind the what” or just simply don’t have time to enjoy lots of weather geekery, scroll to the bottom where I’ll put my snowfall map and a concise forecast. Maybe you’ll even see a map interesting enough to read about on the way down!

The Pattern

Upper Air (300mb) Pattern At 7 AM This Morning. Image Credit: Meteocentre
Upper Air (300mb) Pattern At 7 AM This Morning. Image Credit: Meteocentre

The upper level pattern is relatively zonal today meaning that winds are mostly blowing west to east and there are no significant disruptions in the flow (storms, blocking highs, etc.). This will change to a certain extent in the next 24 hours but it’s important to remember that the overall zonal flow will prevent this storm from sitting and dumping. Also notice the lack of any substantial blocking high pressure over NE Canada. The zonal flow and lack of blocking means that this storm will be a fast mover and totals will be limited by the short duration of heavy snow. That doesn’t mean some hefty numbers will be recorded, it just means that this storm probably isn’t one for the record books.

Surface Pattern At 7 AM This Morning. Image Credit: NWS OPC
Surface Pattern At 7 AM This Morning. Image Credit: NWS OPC

At the surface, the setup isn’t quite ideal for a major storm but it does show that heavy snow is likely across the interior. The limiting factor for coastal Maine and New Hampshire will be the lack of deep cold air. This is a function of a) the zonal pattern discussed above, and b) the relatively weak high to the north and the relatively strong high to the south. This means the high to the south will be the primary driver of a) the flow ahead of the storm and b) the antecedent airmass. For big snows along the coast, we need a strong high to the N/NW to lock in the cold air and keep the cold air flooding south through the storm. This will not be the case tomorrow evening. As for the low pressure systems, the primary low was over MN this morning (it is now over SW Ontario) and the secondary low (our storm) was over northern OK (it is now over AR/SW OK).

The Onset

Kachelmann Swiss HD Model Showing Light/Moderate Snow Arriving Tomorrow Afternoon. Credit: Kachelmann
Kachelmann Swiss HD Model Showing Light/Moderate Snow Arriving Tomorrow Afternoon. Credit: Kachelmann

Snow will move into the area beginning in SW NH late tomorrow morning and ending up in the Augusta area by sundown. There are some indications precip will begin a little earlier in the Portland/Midcoast area as snow showers move in off the ocean but we’ll have to wait until mid afternoon for any more meaningful snowfall. Precip will begin as a period of snow for most if not all areas but will quickly change to rain along the immediate coast (east/south of rt 1). By sundown tomorrow, a couple of inches will be on the ground over SW NH with dustings elsewhere.

18Z NAM Showing Coastal Low Pressure Developing Thursday Afternoon. Image Credit: Weatherbell
18Z NAM Showing Coastal Low Pressure Developing Thursday Afternoon. Image Credit: Weatherbell

As the evening wears on, heavier bands of snow will begin to pivot into the area as coastal low pressure kicks into gear offshore. Guidance is hinting at two circulations being present initially. Which one becomes dominant will dictate which track the low takes and thus how much warm air can wrap into the coast. If the western circulation develops, the storm will track farther to the west and the coast will be warmer, warm enough perhaps for all rain. If the eastern circulation develops, the opposite would happen with the coast seeing slightly more snow. The difference here is not between 3 and 12″, it is rather between 0 and 3-6″. This is not a storm for the coast to see big snows but if the eastern track pans out, the coast would see moderate accumulations as opposed to light/nonexistent accumulations.

The Blitz

12Z GFS Showing Intense 500mb Dynamics Thursday Night. Image Credit: Accuweather
12Z GFS Showing Intense 500mb Dynamics Thursday Night. Image Credit: Accuweather

Precip will begin to fall very heavily as powerful mid/upper level dynamics move into place Thursday night. At 500mb, it’s hard to imagine a better setup for rapid cyclogenesis. The shortwave trough is negatively tilted and a very strong vortmax is racing NNE out ahead of it. Winds ahead of both the vort and the trough are strongly divergent which favors intense upward motion across the entire area.

12Z NAM Showing Strong Jet Dynamics Contributing To Rapid Cyclogenesis Thursday Evening. Image Credit: Accuweather
12Z NAM Showing Strong Jet Dynamics Contributing To Rapid Cyclogenesis Thursday Evening. Image Credit: Accuweather

Another factor aiding in explosive cyclogenesis will be favorable jet dynamics in the upper levels of the atmosphere. The polar outflow jet of the storm is forecast to be situated in such a way that its right entrance region will overlap with the left exit region of the inflow jet to the south/south-west. This overlapping of zones favorable for divergence will allow the storm at the surface to rapidly strengthen, deepening around 20mb in 12 hours!

12Z GFS Showing Extremely Intense Upward Motion Thursday Evening. Credit: Accuweather
12Z GFS Showing Extremely Intense Upward Motion Thursday Evening. Credit: Accuweather

What does all this divergence mean? Upward motion Thursday night will be truly incredible. When the scale ends at 20 and values are forecast to exceed 70, you know the event is highly anomalous. The rapid deepening of the surface low, the intense vort at 500mb, and the jet dynamics at 300mb will combine to lift the air at a very high rate. What does this mean for us? Precip will be falling and it will be falling hard.

NAM 3km Simulated Radar Showing Very Heavy Precip Thursday Night. Credit: Tropical Tidbits
6Z NAM 3km Simulated Radar Showing Very Heavy Precip Thursday Night. Credit: Tropical Tidbits

A band of precip will set up Thursday evening across eastern NH and western ME that will feature whiteout snow falling at rates of 1-3″/hr+, torrential downpours along the coast, very strong winds, and possibly thunder. The fact that precip will be falling so heavily is important because of a phenomenon known as dynamic cooling. When there’s so much upward motion and so many snowflakes melting into raindrops, the atmosphere (especially the above freezing parts) will cool rapidly. This is the key to snowfall east of I-95 and N/W of the peninsulas. The next paragraph explains dynamic cooling and is borrowed from last evening’s update.

As snowflakes melt, the water they contain goes from solid (frozen) form to liquid form. This phase change requires outside energy to energize the water molecules into moving around more, thus changing the phase from solid to liquid. Where does this energy come from? The air around the melting hydrometeors (a fancy word for water (hydro) that falls from the sky (meteor) ). What happens when you remove energy from the air? It cools because, by definition, air with less energy is colder. If you have tons and tons of snowflakes melting at the same time, the temperature will continue to cool and eventually, the entire column will cool below freezing and snow can reach the ground. This process is aided by the intense lifting as air rises, cools, and is replaced at the surface by colder air moving in from the NW.

12Z GFS Showing Poor Dendritic Growth And A Deep Warm Layer In Portland Thursday Night
12Z GFS Showing Poor Dendritic Growth And A Deep Warm Layer In Portland Thursday Night

The problem along the coast is that the dynamic cooling has a lot of warm air to overcome. The warm layer in Portland is modeled to be around 5,000 feet deep by most guidance. Some models are colder but not by a lot. While melting and lifting will cool the atmosphere a bunch, it likely won’t be enough to get significant accumulations. The accumulating snow along the coast will come at the very end as cold air rushes in from the west while precip moves out. IF the easterly track pans out, the warm layer would be shallower and the dynamic cooling would have a chance at cooling the column enough for more substantial snows near the coast. As I mentioned above, there is a cap on snowfall potential east of I-95. I’d say this is about 6″ which would only fall in this area if a) the storm tracked a little east, b) the dynamic cooling worked out as strong or stronger than forecast and c) moisture aloft continued to keep snow falling longer as cold air rushed in behind the storm Friday morning. If none of that happens, most coastal areas would only see an inch or two at best and parts of the midcoast could see no snow at all.

The Wind

NAM Model Showing Two Rounds Of Strong Winds Thursday Night. Image Credit: Weatherbell
NAM Model Showing Two Rounds Of Strong Winds Thursday Night. Image Credit: Weatherbell

Besides the heavy precip, the other big story with this storm will be the wind. There will be two rounds of very strong winds, one on the front side of the storm and one on  the back side. On the front side, winds will be out of the ESE along the coast with gusts to 60mph possible along the midcoast. Gusts to 50-55 mph are likely in the Portland area and points along the coast SW of that. On the back side, winds will flip to the west and begin blasting at similar speeds. While the front side winds will be mostly a coastal issue, the westerlies on the back side will impact everyone.

12Z NAM Showing Two Blasts Of Wind Along The Coast Thursday Night
12Z NAM Showing Two Blasts Of Wind Along The Coast Thursday Night

Here’s another visualization of the winds at a single point (Rockland) through time. Much like a hurricane, there will be front side winds, a calm period as the center of the storm passes overhead, and then back side winds. Winds will not be of hurricane strength though a gust to hurricane force can’t be ruled out offshore and possibly at an exposed Midcoast point. These winds will definitely be strong enough to knock down trees and power lines especially those anchored in soggy ground (midcoast) or those weighed down by heavy snow (inland). With colder air moving in behind this storm, it will be important to be prepared for a night or two in the cold should your power go out.

Snowfall Forecast
Snowfall Forecast

Here’s the latest snowfall forecast. The main adjustment was to trim back totals a bit near the coast as guidance has shifted towards a warmer solution. The bullseye of around 2 feet in the Whites/Mahoosics still looks good. The area with the sharpest gradient (near the coast) still has a bit of uncertainty attached as some guidance still wants to hang onto a colder solution. This will be watched and any adjustments needed made tomorrow.

To summarize: snow will arrive from SW to NE midday tomorrow and will change to rain along the coast tomorrow evening. Heavy snow and rain will arrive tomorrow evening and last through tomorrow night with whiteouts possible in areas of heavy snow. Thunder will also be possible as dry air moves in aloft and instability is created with warmer and moister air near the surface. Winds will be strongest along the coast and will blast the area in two parts. The first will be along the coast with ESE winds gusting up to 60mph. The second will be enjoyed by everyone with WNW winds gusting up to 50mph. These winds will be strong enough for power outage concerns.

No coastal flooding concerns are expected as tides are astronomically low though a few instances of minor splashover are possible along the midcoast where onshore flow will be strongest.

The pattern doesn’t stop here, more snow is in the forecast for New Year’s Eve night and mixed precipitation may threaten to begin the first week of 2017. I will have an update on those storm threats later this evening or tomorrow.

-Jack

 

Cool And Unsettled This Week

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

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

A Week Of Wild Weather

Hello everyone!

This week will serve as exhibit A for the old saying “If you don’t like Maine weather, wait a few minutes”. Tomorrow, lazy spring breezes give way to summer showers and storms. By Sunday, the brisk winds of fall usher in the snows of winter which could drop several inches of snow come Tuesday morning. Not a fan of the snow? By late next week, temps in the 60’s are on the table once again along with rain.

Spring/Summer: Warm And Showery Tomorrow

12Z 4KM NAM Showing Weak Instability Tomorrow. Image Credit: COD
12Z 4KM NAM Showing Weak Instability Tomorrow. Image Credit: COD

Today’s warm breezes continue tomorrow bringing in warmer and, believe it or not, humid air. Dewpoints will rise to near 60 tomorrow which will feel humid this time of year. Temps will range through the 60’s for most. The warm humid air will fuel afternoon showers and storms with the best chance for rumbles in the mountains where the atmosphere is a tad more juiced. No severe weather is expected tomorrow but when thunder roars, go indoors.

Fall: Brisk Winds Deliver Arctic Air Sunday

12Z GFS Showing The Delivery Of Cold Air Sunday. Image Credit: Weatherbell
12Z GFS Showing The Delivery Of Cold Air Sunday. Image Credit: Weatherbell

After getting Spring and Summer out of the way tomorrow, Fall takes over Sunday as a clipper moves through. Rain showers will change to snow squalls as low pressure develops offshore and races east. Winds will be quite gusty as well. On Monday, temps likely will stay near or below freezing as cold air pours in. This sets the stage for the more sizable snow threat on Tuesday.

Winter: Snow Threat Tuesday

12Z GFS Showing A Troublesome Setup Tuesday. Image Credit: Accuweather
12Z GFS Showing A Troublesome Setup Tuesday. Image Credit: Accuweather

Sunday’s cold front stalls offshore Monday as a clipper blasts SE from Alberta. The clipper will move offshore Monday night and a strengthening, negatively tilting upper level trough will help it to intensify. Uncertainty still remains as to the exact track of this storm and thus the exact impacts though some accumulating snow seems likely along the coast. Snow likely moves in Monday night and lasts through Tuesday afternoon. Guidance is fairly far offshore with this storm at the surface but the upper air pattern is giving strong indications that this is likely to drop at least a couple inches along the coast, perhaps a little more.

Spring Returns: Warming Up Late Next Week

12Z GFS Showing The Possible Return To Spring Later Next Week. Image Credit: Accuweather
12Z GFS Showing The Possible Return To Spring Later Next Week. Image Credit: Accuweather

As we head into the latter part of next week, the pattern is likely to modify a bit. The longwave trough in the east is likely to remain but looks to retrograde slightly west and weaken. A flatter pattern out west will allow for the Arctic connection to be cut off and ridging is likely to build over the area. All that jargon translates to a return to normal or above normal temps by the time next weekend rolls around. Current guidance is hinting at heavy rain accompanying this increase in temps but it is far too early to tell specifics. Just know warmer temps are on the way.

A Note On Spring Updates

It’s that time of year again, the sun is out, the birds singing, and the snow flying (sometimes). Spring is here and with it comes Outdoor Track season. Unfortunately, my practice schedule will not allow for evening updates beginning either next week or the week after. I’ll still have morning updates every morning but getting home at 6:30 doesn’t leave a lot of time for forecasting. While I’ve developed a solid system for time management, sometimes high school obligations get in the way.

Thank you all for your patience and continued support, it means a lot.

-Jack