[12Z GFS forecast map for Wednesday afternoon]
The first significant snowfall of the season is on the way for many parts of the Mid-Atlantic region. Low pressure will develop over the eastern Gulf of Mexico on Tuesday night and intensify as it tracks northeastward along the east coast on Wednesday. The low is expected to pass just east of New Jersey on Wednesday evening before reaching the New England coastal waters late Wednesday night. This coastal storm will have a big impact on the Mid-Atlantic region on Wednesday and Wednesday night resulting in rather typical fashion of generating more snow to the north and west and less snow to the south and east. Odds are against much accumulation of snow at or near the immediate coastline given the fact that the air mass will be only marginally cold for snow and there will be no blocking cold high pressure system to the north of here.
As far as travel is concerned, precipitation from this coastal storm will be an all-day affair in the region from DC-to-NYC, but the earlier in the day one can drive the least likely snow will become a problem. Roads will take awhile to become slippery given the warmth of today and the expected relative warmth of tomorrow. The worst driving conditions should occur from late Wednesday afternoon through Wednesday evening when the sun loses its effectiveness on the roads (yes, it has an effect even on overcast days). Of course, the best advice of all for those planning to travel would be to drive on Tuesday if at all possible.
Precipitation should overspread the region from the southwest early Wednesday morning. Precipitation should be mainly rain during the daylight hours from I-95 to points south and east, and mainly snow well to the northwest (e.g., Hudson River Valley). As colder air gets drawn into the system, the rain-snow line will drop southeastward during the day and the precipitation should change to snow in the immediate I-95 corridor by later Wednesday and continue as snow Wednesday night. The last area to change over to snow will be across Long Island and they can expect the least amount of snow. Northerly winds are forecast to increase to 10 to 20 mph on Wednesday with gusts to 25 or 30 mph possible. The snow will be of the heavy, wet variety.
Preliminary snowfall estimates
3-6 inches of snow in the far northern and western suburbs (e.g. interior northern NJ),
1-3 inches of snow in the NYC metro region and immediate surroundings,
<1 inch across Long Island
Stay tuned, still some time to go before this event.
7:00 AM | **Possible record-breaker today; rain-to-accumulating snow scenario on Wednesday/Wednesday night with several inches of snow possible to the north and west of the metro region**
Mostly cloudy with an occasional residual shower possible, but much of the day will be rain-free, unseasonably warm, high temperatures this afternoon not far from 70 degrees
Mostly cloudy, breezy, turning cooler late, lows in the upper 40’s by morning
Mostly sunny, cooler, low-to-mid 50’s
Mostly cloudy, colder, mid 30’s
Cloudy with rain in the morning that should changeover to snow during the afternoon from northwest-to-southeast and continue as snow at night, several inches of snow are possible in the N and W suburbs of the metro region, highs near 40 degrees
Partly sunny, breezy, cold, maybe a snow shower or two, low 40’s
Partly sunny, quite cold, near 40 degrees
Mostly sunny, quite cold, upper 30’s
Today will turn out to be the warmest day of the week – perhaps even in record-breaking territory - as temperatures peak near the 70 degree mark. A couple of lingering showers are possible early today, but much of the day will turn out to be rain-free. A cold front will pass through the region overnight and this will begin a downward trend in the temperature pattern. High pressure will follow for tomorrow, but then a strong coastal storm will mess up holiday travel plans on Wednesday. Rain is likely to begin early in the day on Wednesday, but as the storm pulls to the north and east and colder air is drawn in, the rain should change to snow from northwest-to-southeast during the afternoon hours and continue as snow Wednesday night. Preliminary snowfall accumulation estimates include the following: up to 6 inches in the N and W suburbs, up to 3 inches in the NYC metro region, and lesser amounts to the south and east with the least snowfall likely on Long Island. Stay tuned, still 48 hours to go on this one.
[Surface forecast map for Thursday morning by the 12Z GFS-parallel model; map courtesy tropicaltidbits.com]
Yes, a significant warm up is about to take place in the Mid-Atlantic region; however, it will be short-lived and colder air will return to the area by the middle of next week. In addition, there are reasons to believe that a storm may organize near the Mid-Atlantic coastline during the middle-to-latter part of next week at the same time colder air is becoming more and more established in the region.
The warm up
Temperatures will climb into the 50’s on Sunday in the I-95 corridor and then peak on Monday well up in the 60’s with an outside shot at a record-breaking 70 degrees in some isolated spots. A cold front will pass through the region by Tuesday and that frontal passage will begin a downward trend in the overall temperature pattern. High temperatures around here should drop to the 50’s on Tuesday and then the 40’s on Wednesday. Once this cold front moves off the east coast early next week, it’ll tend to stall out in a north-to-south orientation and this boundary zone may then play a pivotal role in the weather pattern later next week.
Cold and snow threat
By the middle of next week, colder air will become better established in the Mid-Atlantic region and abundant moisture will become aligned with the stalled-out frontal boundary zone just off the east coast. One upper-level short wave will ride up the east coast in the Wednesday time frame and then a second wave will follow close behind. It is this second upper-level short-wave (bigger circled area on 500 millibar height forecast map below) that will become the crucial player later next week as it ultimately will help to allow low pressure to ride up along the east coast. Depending on the exact timing of the interaction between this second wave and all that moisture sitting along the coastline, the result could be some snowfall in the I-95 corridor anytime from early Wednesday to later Thursday. Not all computer forecast models are in agreement with this threat and we'll see how things evolve over the next few days. The forecast maps in this posting come from today's 12Z updated GFS computer forecast model (called "GFS-parallel") and the latest 12Z European forecast model also contains a snow threat for later next week. Stay tuned.
[500 millibar height forecast map for Thursday morning by the 12Z GFS-parallel model; map courtesy tropicaltidbits.com]
7:00 AM | Colder today, but significant (albeit temporary) warm up begins on Sunday and peaks on Monday
Mostly sunny, breezy, colder than yesterday, highs in the mid-to-upper 30’s
Mostly clear, winds diminish, quite cold, lows in the mid 20’s
Mostly sunny, cold, low 40’s
Mostly cloudy, chilly, cannot rule out a shower, mid 30’s
Becoming mostly cloudy, noticeably milder, periods of rain at night, low-to-mid 50’s
Mostly cloudy, quite mild, occasional showers, mid-to-upper 60’s
Partly sunny, breezy, cooler, mid 50’s
Mostly cloudy, colder, chance for some rain or snow, upper 40’s
A reinforcing shot of Arctic air moved in overnight and high temperatures this afternoon will be confined to the 30’s and there will be a noticeable wind chill. Winds calm down tonight and Saturday will be a tranquil day with plenty of sunshine, but still on the cold side. A significant warm up begins on Sunday and then peaks on Monday, but it will be accompanied by some more rainfall. The 50's are likely for highs on Sunday, 60's on Monday and perhaps even a flirt with the 70 degree mark and a record-breaker, and then we'll drop back to the 50's for Tuesday. Periods of rain are likely on Sunday night along with the warmer conditions and lingering showers are likely on Monday. Even colder air pushes in by the middle of next week in time for the Thanksgiving Day holiday and we'll have to watch an area of moisture that will likely ride up along the coast at mid-week as it could back in far enough to the west to produce some problems here around Wednesday.