Heavy Rain/Snow, Winter Weather

A Messy Wednesday On The Way

While some of you saw a few snowflakes this morning, there’s a lot more on the way tomorrow, and it’s going to make a mess of your afternoon commute.

gfs.prateptype_cat.us_ne.2018020612-loop

GFS forecast for the progression of Wednesday’s storm system. Loop provided by Pivotal Weather.

 

Low pressure will move out of the Tennessee Valley tonight, and head towards Southern New England. With high pressure over Atlantic Canada, we’ll have some cold air in place to start the day before the clouds quickly fill in by daybreak. When the precipitation moves in around midday, it should start as snow for most of us. However, it’s not going to stay that way.

Warmer air will move in off the Atlantic, quickly changing the snow over to rain across Cape Cod, with little to no accumulation. The changeover will also take place by early to mid-afternoon across southeastern Massachusetts. In these locations, mainly south and east of Interstate 95, accumulations of 1-3 inches are expected before it goes to rain. Farther to the north and west, things get a little more complicated.

NWS NDFD 2.5-km Mass & CT & RI 2-m Daily High T 2

Temperatures may not get above freezing north and west of Boston on Wednesday, meaning freezing rain could be a threat for some areas. Image provided by Weathermodels.com

That warmer air may not penetrate much farther inland than I-95 at the surface, but aloft, it probably will. When you’ve got below-freezing air at the surface and above-freezing air aloft, you get freezing rain (or sleet) – something we’ve already dealt with several times this winter. While many of the models are trying to send temperatures into the middle to upper 30s, we’re not buying it. The models almost always try to move warm air in too quickly, so we’re ignoring them. We do expect a change to freezing rain from the I-95 corridor up into the Merrimack Valley during the afternoon and evening, which will limit snowfall accumulations a bit, but also drop a layer of ice on top of everything, potentially making even more of a mess of the afternoon rush hour. For these areas, we’re expecting snowfall totals of 2-4 inches closer to I-95, and 3-6 inches up into the Merrimack Valley, as well as over towards the Seacoast of New Hampshire.

Farther inland, across interior southern New Hampshire, there are fewer questions, but everything isn’t set in stone just yet. Some freezing rain is possible, especially along the MA/NH border (including places like Salem, Nashua, and Manchester), but we’re not completely convinced that it will happen. This is something that really can’t be determined until the storm is ongoing and we see how far northward that warm air penetrates. For now, we’re allowing for this possibility, and conservatively forecasting 4-8 inches of snow. If there is no changeover, and the precipitation stays all snow, then amounts could be a bit higher, with totals of 6-10 inches becoming more common. Once you get north of Manchester, from Concord up into the Lakes Region, snowfall totals of 8-12 inches should be the norm.

nam_3hr_snow_acc_boston_15

While we don’t agree with how it arrives at these numbers, the snowfall totals from the NAM are closest to what we are thinking. Image provided by WeatherBell.

The snow will come down heavy at times during the afternoon across the region, tapering off during the evening. It looks like places that change to freezing rain or rain should go back over to snow at night before everything finally winds down and ends around midnight, give or take an hour. We’re not expecting much additional accumulation once it changes back to snow, but some places could pick up a half an inch to an inch.

NAM-WRF 3-km Mass & CT & RI 2-m Temperature 56

Temperatures will stay below freezing all day Thursday, so make sure you get the driveway cleared quickly, or you’ll need some skates to get to your car or mailbox. Image provided by Weathermodels.com

Colder air will settle in behind the storm for Thursday and Friday, so anything that you haven’t cleaned up will freeze solid Thursday morning. Another weak system may bring in some light snow Friday and Friday night, but as of right now, we’re not expecting much accumulation from that system.

Standard

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s