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
Good morning all and happy Monday. Look on the bright side, this is the last full work week of 2019.
The active weather pattern continues as a wintry mess is on its way for tomorrow. Depending on location, one may experience periods of snow, sleet, freezing rain, and plain rain.
Monday Morning Satellite – College of DuPage
Tomorrows storm system is slowly taking shape to our southwest. A gathering plume of moisture will form a weak low pressure center and head towards the Northeast. As the storm center slides south of New England tomorrow snow, sleet, and rain will fall throughout the day.
NAM Precipitation Type Forecast; 7p Monday -> 1a Wednesday – Pivotal Weather, LLC.
Each image is 3 hours after the previous. I’ll do the counting for you, most locations receive approximately 10-12 hours worth of precipitation. Warmer air aloft and at the surface work into the equation Tuesday AM and snow changes over to sleet, freezing rain and rain south of the MA/NH & VT border.
Precipitation Type
Here is what I am currently expecting in terms of precipitation types tomorrow.
Anticipated Precipitation Type
Locations outside of those I have highlighted as changing over to rain will remain near or below freezing throughout the storm tomorrow. However, warm air aloft will move in changing the precipitation from snow to sleet and freezing rain.
The thickness of the warm layer aloft and its proximity to the ground determine whether sleet or freezing rain occurs. Below is a helpful graphic from the National Weather Service.
Temperature Profile & Precipitation Type
Freezing Rain Forecast
As for how much freezing rain will fall tomorrow, below is the European Model’s forecast.
ECMWF Freezing Rain Forecast – WeatherBell, LLC
Most locations in Connecticut receive in the ballpark of a quarter inch of freezing rain. Any amount of freezing rain makes for slippery travel conditions (walking, riding, or driving). A quarter inch or more and you start to notice tree limbs and electric wires sagging. If the freezing rain really starts to add up in Connecticut tomorrow, spotty power outages are possible.
Snowfall Forecast
Snowfall Total Forecast
Looking Ahead
A quick shot of arctic air and a few snow squalls move through the region for the second half of the week. The loop below is of atmospheric temperature anomaly (departure from average). Pay attention to the big purple blob in central Canada.
850 mb Temperature Anomaly – WeatherBell, LLC
This shot of cold air will lead to temperatures Thursday and Friday morning in the single digits. Thursday is quite chilly with temps struggling into the upper teens and low 20s. Fortunately it doesn’t stick around and temperatures rebound nicely.
Right now Christmas Week looks rather uneventful with only a couple passing snow showers.
-Chris
Have you noticed how busy the weather pattern has been lately? From October 1st to yesterday (12/11), Worcester, MA has recorded precipitation 37 out of 72 days (51%). Looking ahead that active pattern should continue through the next week with storm systems on tap for the weekend and potentially next Tuesday.
The below loop from the American GFS model is for the next 7 days highlighting the next two storm threats.
7-day Precipitation Forecast (GFS) – Pivotal Weather, LLC
The first of which is for this weekend as a large storm system moves northward from the Southeast states and brings a soaking rain to the Northeast.
Storm #1 – Weekend System
Late Friday afternoon an area of low pressure forms near the Gulf Coast and begins its journey northward. Travelling up the spine of the Appalachian Mountains this storm system will bring periods of heavy rain up and down the east coast. Little if any snow accumulations are expected with this storm system anywhere.
Saturday is likely a lost day across New England with heavy rain expected in the morning and occasional downpours during the afternoon. With the storm center to the west, meaning winds out of the south, temperatures should spike into the low 50s Saturday afternoon and evening. Colder temperatures don’t return until Monday.
Friday 7p -> Sunday 1p – Pivotal Weather, LLC
While Saturday is a washout, Sunday is mostly dry, but will be quite windy. Note how tightly packed the black contours (which represent equal lines of atmospheric pressure) become as the low pressure center traverses the Northeast and moves into eastern Canada. Now a good rule of thumb for maximum potential wind gusts is the difference in pressure between the low pressure and high pressure systems in the equation.
In the last frame above, the low pressure center has a pressure of 969 millibars (millebars is a unit that measures atmospheric pressure). At the same time, an area of high pressure centered over Minneapolis has a pressure of 1025 millibars. Which gives way to a pressure gradient of 56 millebars between the two centers. Meaning that wind gusts on Sunday could be upwards of ~55 mph.
Below is one computer model simulation of potential wind gusts for noon on Sunday. This model solution is projecting a large area of wind gusts in the 40-50 mph range.
12p Sunday Potential Wind Gusts – WeatherBell, LLC
Storm #2 – Tuesday
As previously mentioned, colder air returns on Monday setting the stage for a more wintry system during the day Tuesday. Right now it appears that the Tuesday storm will be weaker in nature but it has the potential to bring a prolonged period of light to moderate snow to many.
Tuesday 1a -> Wednesday 1p – Pivotal Weather, LLC
Tuesday morning light to moderate snow moves into the region from southwest to northeast. Light precipitation continues for much of the day and into the overnight hours. There are some questions with regards to overall storm track in the modeling with some guidance being further north and some being further south. But overall the loop shown above is a fairly decent representation of the middle ground.
It is much too early for a snow map, but the graphic below highlights the probability of a location receiving >3″ of snow from the system. Right now most locations have a 50% chance of exceeding 3″.
Probability of >3″ of Snow (ECMWF ENS) – WeatherBell, LLC
I certainly have my eye on Tuesday and will have an update this weekend.
-Chris
Hello everyone and a happy Monday to you all. After a rather warm and wet Monday & Tuesday a few snow flakes are possible overnight Tuesday into Wednesday morning. I’m not expecting anything major in terms of snow accumulations, just enough to require a snow brush and maybe a quick shovel before heading to work Wednesday.
A low pressure system over the Great Lakes is driving Gulf of Mexico moisture up the east coast. Remember that surface winds around a low pressure flow counter-clockwise. Meaning that on the east-southeast side of the low pressure system, winds are out of the south/southwest. Which ushers in moisture and warmer temperatures setting the stage for today & tomorrow’s rain.
Monday PM PWAT – Pivotal Weather, LLC
Eventually, the storm center and associated cold front push through the region allowing colder temperatures to move in from the northwest.
Tue AM -> Wed AM Temperatures – Pivotal Weather, LLC
Just as colder temperatures overtake the region, a weak system riding along the frontal boundary will trigger a round of light precipitation over Southern New England. Temperatures are expected to be cold enough to support snow.
Precipitation Type: Tue 7p -> Wed 4p – Pivotal Weather, LLC
Each frame in the loop above is 3 hours long. While it appears to snow for 6-9 hours in most locations, snowfall amounts won’t be too high. Mainly enough to whiten everything up again.
Before I get to my snowfall map I wanted to point out the Boston National Weather Service office’s (located in Norton, MA) current snowfall map.
Boston NWS Snowfall Forecast
When you compare it my map below, you will notice that the NWS is much more “bullish” than I am when it comes to snowfall accumulations. In my opinion, the NWS map represents the “perfect” scenario where everything break right from a snowfall standpoint.
Generally I am expecting a widespread 1-2″ with a narrow corridor of 2-3″. Maybe if someone sits under a heavier band for a prolonged period they could pull out 4-6″, but I’m just not confident in that at this time.
Overnight Tuesday & Wednesday AM Snowfall
-Chris
The first major winter storm of the season is upon us. The storm system that could bring upwards of 12-18″ of snow to Southern and Central New England has had an interesting life cycle as it has traversed the continental United States. First it came ashore at near record strength along the Oregon and Northern California coast with a measured wind gust of 106 mph. Second it redeveloped into a blizzard for the upper plains where it dropped 1-2′ of snow in South Dakota. And finally as a significant storm system for the northeast before finally exiting stage right out into the Atlantic and eastern Canada.
For New England, this system will really come in three parts.
Part 1: Overnight Sunday into Monday Morning
Sunday Afternoon Radar Loop – College of DuPage
The Sunday afternoon radar shown above highlights part 1 of this storm system. While the primary area of low pressure spins over the state of Indiana, warm, moist air is advected northward ahead of the system. This surge of warm, moist air from the south leads to a burst of snow this afternoon and into the overnight.
One models projection for how part 1 plays out tonight is shown below.
Part 1: Sunday PM -> Early Monday AM – Pivotal Weather, LLC.
I picked this model simulation because it highlights a two important aspects of the forecast. The first being that as daybreak Monday morning approaches precipitation rates will drop off. The second being that warm air aloft may overspread SNE and flip many locals to sleet, freezing drizzle and perhaps plain rain.
Here is my thinking for snow totals associated with just Part 1 (i.e. what you wake up to tomorrow morning)
Sunday PM -> early Monday AM Snowfall
Part 2: Monday
During the day Monday will be an in between period with off & on precipitation as the surge of warm, moist air dies and the secondary low pressure forming south of the region gains steam.
Monday AM -> late Monday PM – Pivotal Weather, LLC
As shown above, precipitation rates aren’t very high during the day Monday and into the overnight hours. Many places will either receive light snow or freezing drizzle. Please be careful as some spots may be very slick.
The low pressure center which forms near the New Jersey coast will east-northeast passing near Nantucket Monday evening. As it does, the radar will fill back in and most areas flip back to snow.
Here is my anticipated snowfall accumulations for Monday. I included a plus sign in the ranges to cover those regions that may sit underneath a heavier snow band. Locally higher amounts are possible if a band sits over an area.
Part 2 Snowfall: Monday AM -> late Monday PM
Part 3: Overnight Monday into Tuesday (The Wild Card)
Now for the area of the forecast with the least amount of confidence. As the storm center intensifies east of the region, does it wrap up close enough to the coast to give eastern New England another round of heavy snowfall?
Here are two model projections where the first shows the upper end potential while the second shows the opposite.
Maximum Snow Potential Scenario: 7p Monday -> 7p Tuesday
Part 3 Max Snow – Pivotal Weather, LLC
Minimum Snow Potential: 7p Monday -> 7p Tuesday
Part 3 Min Snow Potential – Pivotal Weather, LLC
The difference between the two scenarios is obvious. The low pressure center wraps up in two completely different locations: 1) due east of Boston near the coast or 2) further northeast in the Gulf of Maine.
Latest computer model guidance has trended towards the maximum snow potential scenario, but the final outcome is likely somewhere in between. Here is what I am expecting for snow accumulations from part 3.
Part 3 Snowfall: late Monday PM -> Tuesday AM
I included plus signs for eastern areas to cover the potential that all things break “right” and the amount of snowfall is maximized.
Storm Total
Storm Total Snowfall
Honestly this storm has a higher than normal bust potential and in both directions. I can foresee scenarios where my numbers are both too high and too low. This isn’t a typical set up and as such the forecast comes with a low confidence level. But the snow map above represents my best estimate at snowfall totals from Sunday afternoon through Tuesday morning.
-Chris
Chris Hampton Weather 