As the headline implies, we’ve got some of the flaky white stuff on the way. This storm is going to be unlike any storm we’ve had all winter. It’s going to be all snow, and the fluffy type at that. It also, may cause problems for your Thursday morning drive to work or school.
High pressure is in place right now, with a cold and dry airmass settled into New England. Temperatures dropped into the single numbers and teens this morning, and at midday, dewpoints were still well below zero. As the high moves off the east, an Alberta Clipper will move in from the west. As it starts to spread precipitation into the region, it will run into this dry air this evening. So, even though the radar may show snow falling, it will evaporate before it hits the ground.
Eventually, the atmosphere will moisten up enough so that the snow will make it down to the ground, and we’ll have some light fluffy snow falling through the overnight hours. It should taper off and end from the west to east right around the time most people head out to work or school in the morning. Road crews should have plenty of time to work on the getting everything cleared before the morning rush hour, but this being New England, where plenty of people completely forget how to drive as soon as they see a single raindrop, well, the snow will probably impact your morning drive, so leave a little extra time.
As for how much will fall, this won’t be a big deal, at least by New England standards. Most of the snow maps you see people post online (like the one below) assume a 10:1 ratio for snow to liquid. In many cases, this will work – 1 inch of rain equates to 10 inches of snow. However, the colder you get, the more the ratio changes. With temperatures in the teens, the ratio could be 20:1. For tonight’s storm, the ratio will probably end up somewhere around 15:1, so, you might expect a little more than the map below is showing. Remember – I also said that the initial burst of snow will likely evaporate before reaching the ground. The model assumes that anything showing up as precipitation does reach the ground, so it will assume we’ve got more precipitation than we actually will get. Plus, nearly every storm this winter has underperformed in the snow department, compared to what the models have forecast. So, factoring all that in, the 10:1 map may actually not be that bad after all.
OK, enough of the caveats and explanations, all you want to know is how much you’ll be cleaning off of your car or driveway in the morning.
Southern New Hampshire: 1-2″
Merrimack Valley/North Shore/Cape Cod/South Coast/Rhode Island: 1-3″
Metro Boston/MetroWest/South Shore: 2-4″
Given the fluffy nature of the snow, if a few places picked up 5″, especially from Worcester County into the South Shore, we wouldn’t be completely shocked.
Another weak system will pass to our south Thursday night into Friday morning, with some light snow possible across the South Coast and Cape Cod, but the storm may end up too far south to impact us at all. Another system passes to the north late Saturday into early Sunday, and this one will be more typical of what we’ve seen this winter, with some light snow changing to sleet, freezing rain and eventually rain. What we’ve actually got our eyes on in the future is Sunday night and Monday. The models have been signalling for a few days the potential for a system to impact us then, but the details have been all over the place. The various models have shown solutions that range from a complete miss to snow to rain, to a heavy snowstorm. There’s still plenty of time for that to come into focus, and we’ll worry about it more as the weekend arrives. For now, we’ll just deal with the light snow tonight.