Hello and a happy Friday to you all! The last weekend of 2019 is upon us and the year is sending the Northeast out with a storm. This one will feature a mixture of all precipitation types for New England. Rain will dominate south, while sleet will be favored for central New England and northern VT & NH. It takes a little while for Maine to get in on the fun, but when the action shifts northeast, snow will fall in Maine.
The Setup
Friday PM Radar – College of DuPage
Outside of western Kansas, the radar across the country is pretty quiet. That doesn’t mean that the atmosphere is at rest though. If you look hard enough at the four corner states of Arizona, New Mexico, Colorado, & Utah; you can make out a faint counterclockwise spin to the radar echos. This is the upper atmospheric energy that is giving birth to the storm system forming over western Kansas.
Saturday & Sunday MSLP & Precip Type – Pivotal Weather, LLC
Over the weekend, this storm system will mature and move northward through the Great Plains dropping upwards of a foot of snow from Denver to Fargo. At the end of the loop, notice how the storm center (follow the red L) gets stuck in southern Minnesota. As if it forgot its passport, the atmosphere won’t let the storm system continue north into Canada and the bulk of the precipitation shifts eastward (look at TN/KY). Eventually that precipitation will make its way to New England.
Sunday
A couple of issues are preventing this from being a solid snowstorm: 1) the air mass isn’t exactly arctic & 2) consistent southerly (warm) flow at the mid-levels of the atmosphere.
Sunday Afternoon High Temperatures – WeatherBell, LLC
Temperatures during the afternoon on Sunday are in the low 40s for southern New England; mid 30s through central New England. Certainly not cold enough for snow.
While warm air will be pushing up from the south in the mid-levels of the atmosphere, there is a small saving grace in the lower levels. A strong high pressure to the north will help to feed in cold air for the first half of the system.
Sunday Evening MSLP & Precip Type – Pivotal Weather, LLC
Remembering that air flows clockwise around a high pressure center, at the surface and lower atmospheric levels, cold air will be supplied for the first half of the storm Sunday Night into Monday afternoon.
Reminder
Temperature Profile & Precipitation Type
What falls from the sky is determined by the vertical temperature profile of the atmosphere. If the whole column is below freezing, then snow will fall. If an above freezing layer of air is above a below freezing layer, then the snowflakes will melt and fall as either sleet or freezing rain.
Monday
Monday Precipitation Type = WeatherBell, LLC
Each frame above is 3 hours and the loop runs from 7p Sunday -> 10p Monday. Precipitation moves in from southwest to northeast Sunday evening and overnight. The color scale may be tough to read:
Blues: Snow
Greens: Rain
Pinks: Freezing Rain
Oranges: Sleet
The battle between cold and warm air is evident in the loop above. Locations that initially start as snow slowly but surely flip to freezing rain and sleet as warm air wins the battle aloft.
A couple inches of snow may be on the ground Monday morning for those locations that start as snow. Eventually, that will be covered by a solid layer of sleet or freezing rain and turn that snow pack into a glacier.
Tuesday
Tuesday MSLP & Precip Type – WeatherBell, LLC
Precipitation intensity will be lighter on Tuesday and slowly but surely the atmosphere will align itself into a more rain vs snow battle as shown by the shrinking of the sleet region (oranges). Little to no snow accumulation is expected in southern New England Tuesday. IF things play out as forecast above, Maine may receive a decent snowfall Tuesday.
Both days look to be pretty miserable with temperatures either side of freezing with either rain or sleet falling. Please be safe travelling to your New Years Eve destinations.
Precipitation Type
Expected Precipitation Type
Not worth worrying about an accumulation map right now. Just know that little to no accumulation is expected south of the Massachusetts Turnpike and north of that a couple inches may be covered by a couple inches of sleet.
Not exactly the most pretty storm system.
-Chris
Chris Hampton Weather 