Tag Archives: rain

A Wintry Mess Midweek Next Week

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Hello everyone!

With today’s Norlun trough fizzling out over the Midcoast and cold air pouring in as forecast, attention can now turn to a mid-week mess due to arrive Tuesday across the area as low pressure passes over the region. Because the low will be passing over us and not to our east, this will be a mix event with a medley of precipitation types including but not limited to rain, snow, sleet, and freezing rain. I’ve covered tonight and tomorrow’s bitter cold several times in the last few days so refer to last night’s blog post for the most recent info on that. Nothing has changed since then. With that said, let’s dig into the Tuesday storm.

12Z GFS Showing The Setup For Tuesday. Image Credit: Weatherbell
12Z GFS Showing The Setup For Tuesday. Image Credit: Weatherbell

The Arctic high pressure containing the bitter cold we feel tonight and tomorrow moves offshore Monday bringing behind it warm SW winds. Temps will rise on Monday but keep in mind, they have a lot to rise as temps Sunday remain largely below 10 degrees. The airmass ahead of the storm is also extremely dry so there will be room for evaporational cooling at the onset of precip. I think we get a good burst of snow at the start of the storm across the area before warm air intrudes from south to north (this looks like a solid front end thump event for those familiar with New England weather terminology). How far north that warm air makes it and how fast it makes it there will determine precip type and thus what accumulations will end up being.

12Z GFS Showing The Arctic High Moving Offshore Monday Evening Leaving In Its Wake Warm Southerly Winds. Image Credit: Accuweather
12Z GFS Showing The Arctic High Moving Offshore Monday Evening Leaving In Its Wake Warm Southerly Winds. Image Credit: Accuweather

How do we go from 20 below zero to rain in a matter of days? The answer lies in the placement of the Arctic high pressure. Notice how the high has departed to the east on Monday and behind it, warm southerly winds are already eroding the cold in place long before the storm gets to us. This is why I’m not super bullish on cold air remaining locked in. That being said, I’ve learned over my time forecasting in Maine that cold air has tremendous sticking power and is not easily moved. This is why I think the mountains stay mainly snow while the rest of the area only briefly sees rain with the exception of the coast where there will be more rain.

12Z GFS Highlighting A Rough Idea For Dominant Precip Type Tuesday Afternoon. Image Credit: Accuweather
12Z GFS Highlighting A Rough Idea For Dominant Precip Type Tuesday Afternoon. Image Credit: Accuweather

In terms of what sort of precip will fall from the sky, the short answer is too early to tell exactly. However, I do feel comfortable roughly outlining my thoughts for general precip type. I think the mountains is mostly snow as the low passes over the coastal plain. They look to remain on the cool side of the low and even if the low passes over the mountains, I think you’d be hard pressed to get enough warm air that far north-west to allow for an extended period of rain. I do think though that the mountains mix with some sort of sleet/freezing rain at some point. The coast is the other higher confidence forecast (relative to the storm in general, confidence is medium at best with any aspect of the storm). The low would have to track significantly farther south than forecast for cold air to remain in place throughout the storm. For coastal areas, look for snow changing to a mix then changing to rain with briefly heavy rain possible. For inland areas, expect some sort of a mix with snow at the onset and rain to finish. What happens in between is anyone’s guess. Confidence will increase in the coming days so stay updated for the latest info.

I’ll try to have an initial guess at accumulations tomorrow evening in my next update on the storm. I’ll have tomorrow’s forecast as usual tomorrow morning.

-Jack

 

Heavy Rain And High Winds Arrive Tomorrow

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Hello everyone!

We’re heading into a period of active weather this week and our first storm is up tomorrow. This one is tracking to our west and thus we’re on the warm side. This will be an all rain event with temps soaring into the 40’s. Winds will also be extremely strong gusting near 60mph at the coast.

Overview

12Z GEM Showing Low Pressure Moving To Our West (Black Arrow) And Heavy Rain Over Our Area (Red Circle). Image Credit: Weatherbell
12Z GEM Showing Low Pressure Moving To Our West (Black Arrow) And Heavy Rain Over Our Area (Red Circle). Image Credit: Weatherbell

Low Pressure is developing over Arkansas right now and will move NNE tonight through tomorrow while strengthening. This storm will drive a cold front through the region tomorrow night.  Ahead of the front, look for heavy rain, strong winds, and warm temps. Conditions behind the front look cold and windy as arctic air moves in. Now that we’ve set the stage, lets dig into the details.

Rain

18Z GFS Showing A Region-Wide 1-2.5" Rainfall. Credit: Weatherbell
18Z GFS Showing A Region-Wide 1-2.5″ Rainfall. Credit: Weatherbell

Rain will move in tomorrow morning and will become heavy by early afternoon. In terms of amounts, a general 1-2.5″ is expected with the highest amounts falling in areas where heavy rain is enhanced by upsloping SE winds. Any SE facing slopes are at risk for the 2-2.5″ totals. With the snowpack being marginal at best, widespread flooding isn’t likely but some rivers and streams could run high enough to cause minor issues in any usual trouble spots. A flood watch is out for much of the area due to this threat.

Wind

12Z GFS Showing Very Strong Winds Just Above The Surface. Credit: Accuweather
12Z GFS Showing Very Strong Winds Just Above The Surface. Credit: Accuweather

I think the biggest story will be the winds. The map at right is the winds just above the surface, NOT winds at the surface. The numbers on the map are knots so the winds between 2,500 and 5,000 feet are hurricane force. NOT all these winds will mix down to the surface by any means. That being said, winds will be very gusty as heavy rain helps to transport winds aloft down to the surface. Winds along the coast especially NE of Portland are likely to gust over 55mph. This could cause a few isolated power outages so watch for those if you usually see darkness during storms like this. All in all, not a massive windstorm but some branches are likely to come down and could cause a few issues. Also be sure to secure anything that might blow around outside (sleds, shovels, etc).

Other Impacts

There could be some thunder in the heaviest precip. Nothing crazy but that’s not something we usually hear here in Maine in January especially with rain (thundersnow happens sometimes with strong Nor’easters but rarely to we break enough into the warm sector for thunder).

On the back side of the storm, cold air will be rushing into the region on strong NW winds. Look for subfreezing air to blast into the area Monday and any leftover puddles will freeze. As a result, look for slick roads Monday and Monday night.

SE winds will be strong tomorrow but won’t last for a long time. As a result, coastal flooding impacts should be minimal. Some splashover/erosion is likely and the usual trouble spots could see some issues but no major impacts are likely.

Cold air moves in Monday and lasts through the week with snow threats midweek and next weekend. Those are still far out so details will have to wait to be figured out.

I’ll have another update tomorrow morning. I’ll also have updates through the day over on the Facebook page.

-Jack

Another Messy Storm On The Way Tuesday

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Hello everyone!

A cold front is currently moving east through the region and will push offshore this evening. Behind it, a sprawling high pressure system will build in straight from Western Canada bringing with it our first real shot of cold air. On Tuesday, warm air from the tropics blasted up the coast by the storm currently causing trouble in Texas will smash into the cold air and a good burst of snow will result. Here’s how I think it will play out and why.

The Cold Air: Tomorrow

12Z GFS Model Idea Of High Temps Tomorrow Showing Very Cold Air In Place. Credit: Weatherbell
12Z GFS Model Idea Of High Temps Tomorrow Showing Very Cold Air In Place. Credit: Weatherbell

Highs will remain below freezing tomorrow for everyone except maybe far southern York County. Highs near the international border will struggle to get out of the single digits. That doesn’t include the NW breeze which will definitely be felt. This is our source of cold air for Tuesday. Prepare for January like temps and wind chills which compared to this torch of a December will feel quite chilly!

The Moisture: Monday Night

12Z GFS Model Showing Moisture From The Gulf Of Mexico Plowing Northward Monday Night. Image Credit: Weatherbell
12Z GFS Model Showing Moisture From The Gulf Of Mexico Plowing Northward Monday Night. Image Credit: Weatherbell

At the same time, the storm that is bringing a slew of problems to Texas will be moving North through the Ohio valley. This will set up a feed of warm moist air from the Gulf of Mexico right up the coast to Maine. This will cause some concerns as the moist air also comes with warmth which will cause concerns for mixing towards the end.

The Collision: Tuesday 

The cold air comes tomorrow and the moisture arrives on Tuesday. The collision is what will cause the snow. At the moment this looks like a front end thump of snow during the day Tuesday followed by a lighter period of mixed snow/sleet/freezing drizzle/drizzle on Tuesday night. Let’s dig into the snow first.

12Z GFS Model Showing Strong Plenty Of Energy To Produce Heavy Snow Tuesday Afternoon. Credit: Accuweather
12Z GFS Model Showing Strong Plenty Of Energy To Produce Heavy Snow Tuesday Afternoon. Credit: Accuweather

As warm air plows northward, it will run into the cold air that arrives tonight into tomorrow. This will allow for heavy snow to form on the leading edge of the warm air as it is forced up and over the cold air. This map from the 12Z GFS shows strong forcing (that’s how the moisture in the air is squeezed out) Tuesday morning. Expect slick roads and heavy snow starting Tuesday morning and lasting through Tuesday afternoon/evening. This is when most of the snow will fall. A general 4-8″ is expected with some seeing more and some less. See the snowfall map below for more details.

Mixing Concerns

12Z GFS Showing Warm Air Aloft Creeping In Tuesday Afternoon. Credit: Accuweather
12Z GFS Showing Warm Air Aloft Creeping In Tuesday Afternoon. Credit: Accuweather

Southwest winds bringing the warm moist air into the region will eventually bring in warm enough air to start causing mixing problems especially in Southern New England. My current thinking is that Warm air aloft gets as far north as the MA state line during the tail end of the steady precip. Lighter precip will linger through the evening and areas as far north as Portland could see some light sleet/freezing rain overnight Tuesday. If warm air moves in earlier/farther north than forecast which is a possibility, totals could be cut down in SW ME and NH. Northeast of route 26 is likely safe from any impactful sleet.

12Z CMC Showing A Tight Temperature Gradient Along The Coast Associated With The Coastal Front. Image Credit: Weatherbell
12Z CMC Showing A Tight Temperature Gradient Along The Coast Associated With The Coastal Front. Image Credit: Weatherbell

The other concern for precip type will be along the immediate coast where a coastal front is likely to form. There will likely be a tight temperature gradient along this front and if you end up on the SE side, temps could rise high enough to change the precip to a rain/snow mix. This threat is greatest along the coast south of Portland and along the tips of the peninsulas. Wherever this sets up, look just to the NW for heavier precip associated with the warm ocean air moving up and over the cold locked in at the surface. Warm air rising over cold air is what is causing this whole mess on a large scale, the same thing happens on a small scale.

Residual Light Precip

12Z CMC Showing Light Precip Lingering Tuesday Evening. Image Credit: Weatherbell
12Z CMC Showing Light Precip Lingering Tuesday Evening. Image Credit: Weatherbell

After the main snow event moves east Tuesday evening, lingering low level moisture will contribute to light mixed precip lingering through the first half of Tuesday night. As warm air completes its invasion aloft Tuesday evening, this could fall any of a number of ways, snow, sleet, freezing rain, or rain. The precip will be light so the impact on snowfall totals will be limited.

low level moisture

I’m thinking that because the moisture is below the warm layers, it stays mostly snow. The warm air moves in at 700mb (10,000 feet or so) but the cold stays tough below that (the blue lines on the map above indicate subfreezing temps at 5,000 feet). The moisture is in the low levels (where the cold air is) and thus even though 700mb is warm, I could definitely see another inch of snow as the snow falls in the low level cold layer. Regardless, this will keep roads slick through Tuesday night despite the heavy precip being gone.

Expected Snowfall

Expected Snowfall
Expected Snowfall

Looking at the final snowfall amounts, I expect a general 4-8″ for Northern New England with less to the south. I think someone sees 10 or 11″ and the best chance looks to be either in the mountains where deep cold stays really locked in contributing to a drier snowfall that accumulates faster or near the coast where the coastal front contributes to more liquid falling from the sky. The coastal ‘jackpot’ area largely depends on the ocean air staying farther SE and the sleet being kept at bay. The northern Jackpot is dependant on enough moisture moving that far north. A coastal low developing Tuesday evening will try to steal some of the moisture from NW areas.

I’ll have another update tomorrow evening on the storm, details on tomorrow’s weather will come tomorrow morning.

-Jack

The First Snow Of The Season Arrives Late Tonight After A Cold Rain

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Hello everyone!

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4:15PM Radar Shows Rain Slowly Expanding NW. Image Credit: Accuweather, Annotations By Me

Rain is already spreading across the area this afternoon as a plume of moisture moves north. The immediate coastline and the inland portion of the midcoast is currently seeing light to moderate rain and this will continue through the evening with rain slowly expanding NW.  Light to moderate rain should continue throughout most of the early part of the night mainly east of the Turnpike.

12Z GFS Giving Us An Overview Of The Storm, Map Credit: Weatherbell, Annotations By Me.
12Z GFS Giving Us An Overview Of The Storm, Map Credit: Weatherbell, Annotations By Me.

The main feature of this storm will be a sharp gradient on the back side of the system with 5 or 10 miles making up the difference between a few sprinkles and a half inch of rain ending as an inch of snow. As a result, the forecast is especially touchy for areas west of the Midcoast where 1-4″ is likely depending on elevation. Once you get to the I-295/I-95 corridor, a very sharp dropoff in snow totals is likely with some areas seeing up to 2″ and others but a few midnight flakes.

20Z HRRR Model IDEA On How The Storm Winds Down Tomorrow Morning. Map Credit: Weatherbell, Annotations By Me
20Z HRRR Model IDEA On How The Storm Winds Down Tomorrow Morning. Map Credit: Weatherbell, Annotations By Me

 

All precip, rain or snow, comes to an end early tomorrow morning with everyone west of I-95 dry by sunup and everyone else soon thereafter. The rest of tomorrow looks cool but nice with clearing skies and NW winds bringing in cooler and drier air.

18Z NAM Showing The Negatively Tilted Trough And The Winds Out Ahead Of It Directing The Storm Westward Up The Coast. Map Credit: Weatherbell, Annotations By Me
18Z NAM Showing The Negatively Tilted Trough And The Winds Out Ahead Of It Directing The Storm Westward Up The Coast. Map Credit: Weatherbell, Annotations By Me

Every storm has a surprise and by virtue of surprises, they largely remain unknown but if there was one place I had to guess there would be a surprise, it’s where there’s been one already. There were indications that the trough at the 500mb level would be negatively tilted with this storm for days. Finally, the surface forecasts caught up to that and in the past 24 hours the forecast has gone from ‘chance of a flurry midcoast’ to ‘many people get their first accumulating snow’. This trend has smoothed out with the afternoon guidance today but don’t be surprised if this thing comes a tad farther west and instead of a dusting, you end up with 2″ of snow. After all, it would really only take 25 miles to make that big of a difference for some.

12Z GFS Showing NW Winds Bringing In Colder (And Drier) Air Which Could Shut Off Precip Early
12Z GFS Showing NW Winds Bringing In Colder (And Drier) Air Which Could Shut Off Precip Early

The other, equally possible surprise is that the same cold NW winds bringing in the cold air to change things over to snow also come with enough dry air to shut off the precip early, especially because NW winds downslope off the mountains which dries the air even more. For a full explanation of downsloping in relation to temperature, check out my neat weather tidbit from a few weeks ago. While that post talks specifically about temperature, the same principle applies to moisture in that when air rises, moisture condenses and forms clouds/precip etc. just like it cools and when it sinks, the opposite happens. The post also includes a general overview on downsloping which applies to this forecast.

While the last two paragraphs could reasonably be perceived as me covering myself in case the forecast goes wrong, my hope is that in case it does, you can at least know why. As I’ve said several times, part of my goal here is to educate you about why weather happens as well as to tell you what’s likely to happen.

2015-11-22_15-51-53

Speaking of what’s likely to happen, here’s a look at how much snow to expect when all is said and done. All in all, not a big deal but it still will be nice to see the flakes flying in November.

I’ll have another update on tomorrow’s weather in the morning.

-Jack

A Quickly Improving Day Today

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Hello everyone!

5:10 AM Radar Showing Very Heavy Rain Across NE Areas With Lighter More Scattered Precip Back To Our West.
5:10 AM Radar Showing Very Heavy Rain Across NE Areas With Lighter More Scattered Precip Back To Our West.

Our long-awaited storm is here and heavy rain is falling across the area with the expected strong winds as accompaniment. The heaviest of rain is north and east of Portland as of 5:15 this morning and this area of intense rain/wind will continue to move NE in the coming hours. Behind that lies a batch of very heavy rain over SE MA and lighter showers over eastern NY. The SE MA rain is moving NE and will likely impact the midcoast with another round of torrential rain and gusty winds. More showers lurk back in NY associated with cold front #1 today and expect one last shot at intense rain and driving winds as this moves through.

HRRR Model IDEA On How Rain Evolves Today. Notice Showers Around 9 AM Then More Showers/Thunderstorms Later In The Evening. Credit: Weatherbell

Behind those showers, which arrive 9-10 AM, expect clearing skies and warming temps. By mid/late afternoon, temps in the 70’s are likely under partly sunny skies. Another cold front moves through this evening which touches off some showers and possibly a few thunderstorms too. For a minute, it just may feel more like August than October. Temps drop a bit behind the front but a continued stretch of very mild weather looks to be on the way for the next week or so.

-Jack

Heavy Rain And Wind Moves In Tomorrow Evening

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Hello everyone!

Not too much has changed since yesterday in terms of our upcoming heavy rain event. Here’s a quick updated rundown of what to expect.

Rain

12Z Canadian HRDPS Model Showing Deep Mositure Flooding Into The Area On Strong SE Winds. Map Valid 6AM Thursday. Credit: Weatherbell
12Z Canadian HRDPS Model Showing Deep Moisture Flooding Into The Area On Strong SE Winds. Map Valid 6AM Thursday. Credit: Weatherbell

Rain moves in during the evening hours tomorrow arriving in SW areas around 5 or 6 tomorrow evening with most of the area seeing rain by 7 or 8 PM. The heavier rain will hold off until later in the evening beginning in the west around 9 and spreading east through midnight. Between midnight and 6 AM or so, expect the worst conditions to occur with heavy rain being driven by strong winds.

NWS WPC Total Rainfall Forecast Through Thursday. Tan/Orange Areas Show 1-2″ Amounts While The Red Colors In The Mountains Show 2-2.5″ Totals. Credit: Weatherbell

While available moisture (Precipitable Water, shown above) is quite high, as well as forcing for wringing out that moisture, the ideal parameters are only really in place for about 6 hours early Thursday morning. As a result, total rainfall will be limited somewhat compared to if this was a more slowly moving system. A total of 1-1.5″ of rain is likely with 2-2.5″ amounts on south-facing mountain slopes.

Wind

12Z GFS BUFKIT Plot Showing 50kt Winds Below The Mixing Layer Early Thursday Morning.
12Z GFS BUFKIT Plot Showing 50kt Winds Below The Mixing Layer Early Thursday Morning.

Winds will become gusty tomorrow afternoon out of the SE as the front approaches. Expect winds building throughout the day with peak gusts arriving in the same 6 hour window as the heaviest rain from 12-6 AM Thursday. Most areas should see 15-25 mph winds with gusts to 35mph while the coast sees 25-35 mph winds gusting to near 60 mph. The plot above shows winds (everything but the yellow line, in knots) and the mixing layer (yellow line). Any winds below the yellow line are eligible to mix down to the surface in heavy precip. In heavy precip early Thursday morning, someone along the coast is likely to see some of those intense winds aloft mixed down on the order of 50-60 mph. The greatest threat for this is the NE coast closer to Penobscot Bay where a wind Advisory is up. All coastal areas should be prepared for strong winds, the chart above is for Portland.

Takeaway

Rain begins tomorrow evening becoming heavy late at night. Winds will also be on the increase out of the SE. Peak rain and wind occurs 12-6 AM Thursday with wind gusts approaching 60 mph along the coast. A total of 1-1.5″ of rain is likely with more on the south-facing mountain slopes where 2-2.5″ is likely.

I’ll have more updates tomorrow in a similar patter to today’s updates.

-Jack

Evening Update On Midweek Heavy Rain Event

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Hello everyone!

Our midweek heavy rain event is still very much on track for Wednesday afternoon through Thursday morning. Tonight’s update will focus more on specific impacts rather than larger scale setups.

Rain

NWS WPC Forecast Rainfall Amounts Through Thursday Afternoon. Credit: WPC/Weatherbell

Heavy rainfall is likely to be the main threat from this storm as Patricia’s moisture streams northward and interacts with the approaching cold front. A general 1-2″ is likely (Tan-Orange shadings on the map) with some 2-3″ amounts likely in the favored upslope areas (reddish shadings on the map). The fast moving nature of this system is what will keep precip amounts relatively low and given the quick arrival of dry air from the west Thursday morning, heavy precip should be centered in the 8PM-6AM timeframe which will limit total rainfall. Rain is likely to arrive earlier in the evening Wednesday likely closer to 5 or 6PM. These details will continue to be refined in the coming days.

Wind

12Z GFS Showing Very Strong Winds Just Above The Surface Early Thursday Morning.
12Z GFS Showing Very Strong Winds Just Above The Surface Early Thursday Morning.

With a strong cold front comes strong winds and this time is no different. A SE gradient will sharpen up during the day Wednesday leading to very strong winds by Wednesday afternoon into the evening. On the map above, the yellow line is the mixing layer and the red/green/blue contours are wind speeds. Elevation is the y-axis and time is the x-axis but read from right to left (I didn’t make the graph I promise! (credit to that goes to BUFKIT)). The takeaway is that any wind under the mixing layer is ‘eligible for a ride to the surface in heavy rain. Given the likely heavy rain early Thursday morning which coincides with the strongest winds just above the surface, very high winds are definitely a concern from midnight Thursday to 6-7AM or so. Expect the highest winds along the coast 20-30 mph with gusts to 55 mph or so. Lesser winds are expected elsewhere. With this kind of wind, saturated ground from the heavy rain, and some leaves definitely still on the trees, scattered power outages are likely especially along the coast.

The tides don’t look to line up particularly well for coastal flooding but some minor splashover is possible in the usually suspect areas.

I’ll follow today’s update pattern again tomorrow with daily weather in the morning and then a storm update in the evening.

-Jack

A Messy Saturday As We Once Again Track The Rain/Snow Line

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Hello everyone!

Quick update this evening to bring you up to date on the latest info regarding our next storm system arriving tonight and hanging out through tomorrow afternoon. For the most part it will be a fast-mover with precip ending in the early afternoon but while it’s here, the mountains could pick up some decent snowfall for this time of year.

Click around on the map to view precip types and approximate changeover times for your local area.

Rain moves into the region in the wee hours of the morning tomorrow and will start as all rain but will quickly change to snow in the higher elevations before dawn. Snow levels will drop as the low intensifies in the Gulf Of Maine and pulls in cold air on the NW side. Expect everyone to see flakes in NH and ME by early afternoon with western MA likely seeing a few flurries as well. It will be a race against time as the cold air rushes SE to try to get to the coast before the precip departs and just who wins is still a bit up in the air.

In every storm there is bust potential and while forecast confidence is pretty high, the exact extent of the rain/snow line as the precip leaves is still an unknown. As of now, it looks like the Maine coast with the exception of a few of the peninsulas will see at least a few flakes with most of coastal MA and all of RI missing out on the white but don’t be surprised if the snow comes in a little earlier than expected and totals are a little higher. Models have tended to place lows to the NW of their actual positions so if this low ends up a little farther SE and a little colder, I wouldn’t be too surprised. With this in mind, while coastal areas don’t look to see any accumulations, a quick coating is possible should a colder solution occur.

A rumble of thunder is also likely across MA RI and CT and some small hail is possible in some of the stronger cells.

Winds will kick up tomorrow as the storm moves out and gusts over 35 mph are widespread so watch for some isolated power outages especially in areas where snow has accumulated on branches and power lines.

I’ll have another update in the morning as the rain/snow line sets up.

-Jack

Mixed Precip Now Underway As Late Season Winter Storm Arrives

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Hello everyone!

Precip is already falling across much of the area as our next storm moves in. Expect snow to flip quickly to freezing rain/rain along the coast but remain all snow inland this evening. Currently, some weak divergence aloft is causing a heavy snow band to move through Cumberland County on its way NE.

925mb_sf
925mb Analysis Showing Divergence Aloft Over Southern Maine/New Hampshire

This divergence is causing a brief heavy snow burst which, despite warm temps, is accumulating on some of the roads so use caution if you happen to be driving this afternoon.

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3:30 PM Radar Showing A Heavy Burst Of Snow Moving NE Across Coastal Areas

Warmer air will continue to flood into coastal regions this afternoon though after looking at data from a special sounding (vertical profile of the atmosphere) from the NWS in Gray, models appear to have had a warm bias with this event and thus a tad more frozen precip is expected especially away from the immediate coast.

HRRR Model Simulated Rader Animation. Credit: Weatherbell

Here is the HRRR model’s take on what the first phase of our storm will look like through the wee hours of tomorrow morning. This model does a good job showing the rain/snow line advancing this evening with heavy snow across the interior and rain across coastal areas. I would advise taking this model with a grain of salt however as it shoots the rain line past Lewiston. When accounting for the warm bias of the models for this event, the rain line should approach the Lewiston area but is not likely to pass it especially considering the snowpack we still have on the ground.

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12Z GFS Upper Level Energy Map. Credit: Weatherbell

The second phase of the storm occurs tomorrow when a strong upper low crosses the area. Expect temps to crash tonight as NW winds behind a developing secondary low move cold air into the region. As a result, tomorrow’s part of the storm will be an mostly snow event which is where the coast picks up their accumulation. There is still some debate as to if/when/where an inverted trough might setup to help focus the precip so uncertainty still remains. Precip looks to move out tomorrow evening from west to east.

snow map 3-14

Here is the latest snowfall forecast showing the coast escaping with little more than a dusting while the mountains see the jackpot with 8-12″. Due to warmer temps, this will be a wet and heavy snow so watch for a few isolated power outages as trees sag under the weight of the snow.

-Jack

 

Slushy Storm To Bring More Snow, Rain To The Area Tomorrow Into Sunday

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Hello everyone!

Another storm is on the way this weekend and while much of the Northeast US sees rain and 40’s for this storm, we lucky Northern New Englanders will likely be seeing more snow. While this will not be a big storm by any means, especially compared to others this winter, it will put a temporary pause on the arrival of Spring.

Water Vapor Image From This Afternoon Showing The Two Features That Will Bring Snow To The Area This Weekend. Credit: SSEC
Water Vapor Image From This Afternoon Showing The Two Features That Will Bring Snow To The Area This Weekend. Credit: SSEC

Looking at the setup for our weekend system, two main features present themselves: a plume of moisture and warm air heading north from the Gulf Of Mexico and an Arctic disturbance racing SE to meet the moisture. How much cold makes it south and how far it gets will be crucial to determining how much snow falls.

12Z GFS Valid At 1 PM Tomorrow Showing Warm Air Streaming In At 2500 Feet. Credit: Accuweather
12Z GFS Valid At 1 PM Tomorrow Showing Warm Air Streaming In At 2500 Feet. Credit: Accuweather

Before precip even starts, SW winds aloft will be allowing warm air to stream into southern parts of the region resulting in very little snow on the front side of the storm. Winds aloft are far weaker inland and thus above freezing air should be mainly a coastal issue with the foothills briefly getting in on the action tomorrow afternoon.

12Z NAM Showing Warm Air Working In Aloft But Staying Firm At The Surface. Vertical Temp Profile For Augusta, Valid At Midnight Tomorrow
12Z NAM Showing Warm Air Working In Aloft But Staying Firm At The Surface. Vertical Temp Profile For Augusta, Valid At Midnight Tomorrow. The Red Line Indicates The Temperature.

Warm air will also be working in at the surface but with 1-3′ of snowpack still on the ground, warming aloft may outpace the warming at the surface tomorrow morning so a brief period of sleet/freezing rain  is possible along the coast and just inland as well. While this doesn’t look like a major concern, watch out for some extra slick spots tomorrow morning.

12Z GFS Showing A Lack Of Intense Upward Motion Resulting In A Lack Of Heavy Precip. Image Credit: Accuweather
12Z GFS Showing A Lack Of Intense Upward Motion Resulting In A Lack Of Heavy Precip. Image Credit: Accuweather

Another key difference between this storm and others this season will be that precip this time around will be a lot more on the steady side rather than extremely heavy. The GFS vertical velocity map above shows this well. Notice the lack of pinks/reds and the introduction of more gentle oranges. This translates to light to moderate precip rather than heavy precip.

precip type map
Expected Precipitation Type For This Storm

By tomorrow afternoon, the warm air will have made its farthest push inland with temps both above freezing both aloft and at the surface all the way into the foothills. During the heaviest rain, flooding could be an issue along the coast where rain and snowmelt could combine to cause some minor street flooding Saturday afternoon/evening. Any impacts from flooding should be minor but it is something to watch for especially along the coast.

12Z GFS Showing A Strong Upper Low That Will Help To Extend Snow Well Into Sunday. Credit: Accuweather
12Z GFS Showing A Strong Upper Low That Will Help To Extend Snow Well Into Sunday. Credit: Accuweather

The final phase of the storm will come Sunday as an upper low dives SE across the area. This will help to continue snow across the area on Sunday which is when coastal areas see most of their accumulations. Flakes will be flying as far south as SE MA but no accumulation is expected south of Boston.

12Z Canadian Model Showing Snow Lingering Into Sunday Afternoon. Map Valid 1 PM Sunday. Credit: Weatherbell
12Z Canadian Model Showing Snow Lingering Into Sunday Afternoon. Map Valid 1 PM Sunday. Credit: Weatherbell

Snow on Sunday will be lighter and more showery in nature but it will help to keep roads slick and flakes falling for most of another day.

snow map 3-13

Taking a look at accumulations, the highest totals will be in the mountains where the cold air will hang tough the whole way through. Amounts drop off towards the coast with Southern New England seeing no accumulation at all.

I’ll have another update in the morning.

-Jack