Low pressure will pass through the area in waves tomorrow night through Wednesday. The track of the main low will be to our west so this will be a snow to mix to rain event even in the mountains. Snow, freezing rain/ice, flooding, and wind threats with this storm. I’ll outline each below broken down by wave. The first wave is the cold phase of the storm with snow and mix while the second wave is almost all rain. There is a chance we see a third wave on Wednesday with more snow but that is far from certain. Let’s dig into the forecast.
Here is the RGEM model for Tuesday morning showing the major players. A storm is moving across the southern Ohio valley right now and will move into VA tonight. It will then move NE along a warm front and that will deliver our first shot of precip. Given how darn cold the air is out ahead of this storm, I am hesitant to jump at warm air blasting in without a fight. That being said, SW winds will have all of Monday to moderate the air before the storm even arrives. Also, the high pressure system containing the cold air will be retreating offshore which means it won’t be funneling cold air into the area through the event. Instead, counterclockwise winds around the high to our east will help promote strong southerly winds which will greatly help warm air coming north.
First Wave: Cold Air Hangs On
The first wave of precip will arrive tomorrow night and will initially be in the form of snow. Several inches will accumulate by Tuesday morning and this will cause the Tuesday morning commute to be messy. Use extra caution and allow for extra time to get to work/school. The mesoscale higher resolution models such as the RGEM and HRDPS are holding the cold air in place much longer than the lower resolution global models. This is a good indication that cold air will hang on unusually long, as it almost always does in Maine in February after an Arctic blast with a solid snowpack on the ground. For those reasons, I am hesitant to believe fully that anyone but the immediate coast changes to rain before midday Tuesday. My time forecasting here has taught me never to underestimate the sticking power of Arctic air.
First Wave: Freezing Rain Threat
As the first wave moves through Tuesday, winds aloft will be blasting the area with a blowtorch, sending warm temps deep into the area. Cold air aloft is easy to displace. However, cold air at the surface doesn’t like to go anywhere in a hurry. The 12Z GEM shows this well. Tomorrow morning, the surface freezing line will hug the surface warm front offshore. The low level cold will dam along the mountains and will generally be sluggish in terms of going anywhere. In between the freezing line aloft and the freezing line at the surface, there is the risk for freezing rain. For the foothills, this could be a respectable freezing rain event with amounts of a tenth to as much as a third of an inch possible. Depending on exactly how much warm air moves in aloft and exactly where in the atmosphere it does, sleet is also possible. The mountains will remain cold enough for snow for most of this time as the upper level warmth won’t quite make it there in time for the first wave. The coast will likely see the surface warm front move just far enough inland to bring temps above freezing leading to rain.
First Wave: Accumulations
Here’s what I’m thinking for accumulations for the first wave from tomorrow night through Tuesday evening. After Tuesday evening, everyone most likely changes over to rain as warm air streams in. This could be a significant enough icing event for the foothills to lead to scattered power outages especially if the inversion can break enough to allow for gusty winds with the second wave Tuesday night. Most of this is washed away Tuesday night with the rain but it will be quite slippery for both the AM and PM commutes Tuesday the more so the farther inland you go.
Second Wave: Cold Air Washed Out
After the first wave departs early Tuesday afternoon, we will see a lull in the action before the main storm passes well west of the area. The initial wave will help lift the warm front north of the region and warm air will begin to stream into the entire area. By the time round two arrives Tuesday evening, almost everyone will be warm enough for rain. Winds will become quite strong out of the south and south east aloft and there is the risk that some of those gusts mix to the surface in some capacity though a strong inversion will keep the serious winds mainly to our south. Especially along the coast though there is the risk for gusts up to 35mph. The warmer your temperature, the higher your risk for winds which is why the coast is at the greatest risk for wind. The mountains and especially the mountain valleys do an exceptionally good job holding on to cold air and I wouldn’t be surprised to see some mountain spots hold on to some variety of frozen precip throughout the whole event. The farther north and west you go the more likely this is. A general .5 to 1″ of rain is expected with this event which could lead to isolated flooding with frozen ground and a little snowpack.
Third Wave: Surprise Snow Wednesday?
The rain moves out quickly Tuesday night and cold air moves back in for Wednesday. Another storm is right on the heels of this one but right now the thinking is it stays south. However, the 500mb setup pictured is dangerous for surprise snow with a long nose of energy pointed right at us. Most likely a storm forms and models are currently thinking it heads well south but I’m not fully convinced yet. Even without a robust surface storm, trouble could still be caused by upper level energy. It is also possible enough dry air moves in behind the rain that we don’t get anything. We’ll have more clarity on this once we figure Tuesday out which might just be on Tuesday.
A period of cool calm weather arrives Thursday into Friday and another storm threatens for Saturday with a mix of snow and rain likely.