Tag Archives: mix

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

 

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.

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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