We've been talking for most of the week about a system that will impact the area tomorrow, with the consensus over the last couple of days being that the state sees mainly rain from this storm. However, todays guidance introduced an interesting wrinkle into the forecast at the last minute, opening the door for a potential period of heavy wet snow tomorrow morning across the northern and elevated portions of the state.
Essentially, the setup is this. A primary low tracks into the Great Lakes this evening, transferring to a secondary low off the coastline tomorrow morning. This low will pass near the 40/70 benchmark, which is traditionally a location that argues for a wintry event for the entire state. However, the primary low ahead of the coastal secondary scours out the cold air aloft, and since there is no strong high pressure to the north to reload the cold eradicated by the primary, the upper levels, and to a lesser extent, the surface, warm to a level that would support rain and not snow. As the system strengthens and it's dynamics overpower the primary, it will cool the column where it is precipitating, but that will not take place until the storm has passed our latitude and thus will primarily benefit areas to our north in the snowfall department, with parts of Maine and New Hampshire seeing several inches of snow from this system.
However, there is some model guidance, primarily the NAM and Euro, that argue for a quicker, deeper storm, and thus, allow the cooling dynamics to enter the northern tier of our forecast area, flipping the northeast and northwest hills over to a period of heavy wet snow tomorrow morning as the low pulls away. It's a setup where everything would have to go right for us to see snow; the primary would have to weaken quick enough, the coastal deepen fast enough, and the forecast air mass come in on the colder side of the forecast guidance to allow such a thing to happen.
The images attached to this post are the total snowfall maps from the NAM and RGEM models over the next 48 hours. You can see that on the NAM, the band of snow comes just far enough south to deliver a couple inches of snow to the far northern portion of the state, while on the RGEM, the edge band is way up in southern New Hampshire! That’s quite the difference considering we’re inside 24 hours, and really shows the volatility and marginality with this setup. The model consensus puts that boundary in northern MA around the NH border, but considering the profile and the consensus readings in the northern parts of our area, the cold solutions are well within the envelope of possibilities and thus we cannot simply discount them. However,it's clear that the distinct consensus forecast among the models is for no snow, which is why you have not seen snowmaps or discussions about this system from us, or anyone else. Meteorologists don't like taking risks.
In some ways, I believe the potential is there for a surprise tomorrow morning. Dynamic cooling is a well-known and well observed phenomenon, and this is a textbook example of it occurring. Furthermore, this whole system seems a bit fishy to me. Synoptically, considering the track that the storm is taking and the temperature profile aloft, I have a hard time believing that the marginal warm layer at the surface is going to persist and not be scoured out by heavy wintry precipitation. If I looked at this setup without looking at the temperature profiles, I would say we’re all going to get some heavy wet snow tomorrow morning. Sometimes as a meteorologist, you have to go with your gut, and my gut is telling me that we haven’t seen all that this storm has to offer just yet.
As such, folks in the northeast and northwest portions of the state, be aware that there’s a chance for a bit of surprise snow tomorrow morning. Don’t expect anything, because there will probably be nothing but some heavy rain and maybe a light glaze of ice with some flurries at the end, but then again, don’t be surprised if when you pull back your curtains tomorrow morning, you see big fat fluffy snowflakes coming down.
On the high end, I see this as being a few inches of snow in the higher terrain tomorrow morning in the 7 AM-Noon timeframe. More likely than not, it’s nothing at all, but should the flip occur, snow will likely be fairly heavy, with rates of up to 1” per hour possible, and so road conditions could quickly go downhill in those areas. Keep a wary eye to the sky tomorrow morning in the northern tier of the state, and may you enjoy whatever you may get!
Have a great weekend, and thanks for reading SCW.