****Icy mess in Mid-Atlantic from late Wed. into early Thurs..... breakdown for DC, Philly, NYC...slippery roads for Thursday AM commute...repeat performance this weekend...snow threat next week****

This forecast map of “total freezing rain amounts” by mid-day on Thursday certainly sends warning signals that there can be big-time Thursday AM commute issues with an icy build-up in many parts of the Mid-Atlantic region. Map courtesy NOAA, Weather Bell

Overview

An active weather pattern will likely bring three winter storm systems to the Mid-Atlantic region during the next week or so. The first system will bring a mix of precipitation to the DC-to-Philly-to-NYC corridor from late tomorrow into Thursday morning and all areas are likely to experience slippery road conditions for the Thursday AM commute. A thin layer aloft of slightly above-freezing air will push into the region on Wednesday night, and this will play a big role in precipitation types ranging from snow-to-sleet-to-freezing rain to just plain rain. Always a difficult forecast when dealing with these thin layers, but my initial feeling on this mid-week threat in the I-95 corridor is as follows: DC metro region will get hit hard with freezing rain leading to a significant ice-buildup, the Philly metro region may have an extended period of sleet, and the NYC metro region may actually see snow for much of the event that certainly can mix with sleet at times. A similar weather event could unfold for the upcoming weekend in the Mid-Atlantic region with a “snow-to-sleet-to-freezing rain-to-plain rain” scenario on the table. Looking past the weekend system, there very well may be an accumulating snow threat for much of the Mid-Atlantic region by the middle of next week and it can be significant.

A thin layer of air with slightly above-freezing temperatures is likely to develop aloft (arrow) by late tomorrow night over the DC metro region and this could lead to an extended period of freezing rain with ground-level temperatures (circled) remaining at or below-freezing in many spots…in other words, quite a slippery mess is coming for the Thursday AM commute. Plot courtesy NOAA, tropicaltidbits.com

Breakdown for DC, Philly, NYC

DC: As moisture arrives later Wednesday or early Wednesday night, there can be a bit of snow and/or sleet; however, precipitation is likely to change to freezing rain in the overnight hours with an icy build-up by Thursday morning; especially, across the normally colder N/W suburbs. On Thursday, temperatures will take awhile to rise above freezing; especially, across the normally colder N/W suburbs. Consequently, there can still be slippery road conditions for the Thursday AM commute...plain rain likely in the mid-day and afternoon with temperatures finally climbing to well above freezing levels.

All it takes is for a thin layer of air with slightly above-freezing temperatures to move in aloft and result in a change from snow to sleet and perhaps ultimately to freezing rain. In this example, the layer aloft (arrow) with slightly above freezing temperatures is very thin by early Thursday morning in the Philly metro region and ground-level temperatures (circled) are still below-freezing. In other words, expect slippery conditions for the Thursday AM commute all across the Philly metro region. Plot courtesy NOAA, tropicaltidbits.com

Philly: As moisture arrives later Wednesday or early Wednesday night, it’ll likely be cold enough for snow, but then a thin layer of above-freezing air will push in aloft and result in a changeover of the precipitation to sleet which is likely to last for an extended period of time in the overnight hours...a sleet festival for many areas across SE PA. By late Wednesday night, the sleet may mix with or change to rain and - with ground temperatures at or below freezing - any rain that falls will freeze on most surfaces. In fact, temperatures will be reluctant to climb above freezing for most of the morning on Thursday across SE PA; especially, in the normally colder N/W suburbs...plain rain is likely by mid-day or early afternoon on Thursday.

When you see lots of colors on a surface map this time of year that is usually not a good thing as it means sleet (purple) and freezing rain (pink) are involved with a precipitation pattern. Indeed, lots of colors on this forecast map for late Wednesday night suggest there can be an icy mess in many parts of the Mid-Atlantic region, and snow (in blue) across the northern half. Map courtesy NOAA, tropicaltidbits.com

NYC: As moisture arrives early Wednesday night, it’ll likely be cold enough for snow, but then a thin layer of above-freezing air can push in aloft during the overnight hours and result in a mixture of snow and sleet. By early Thursday, it is possible that enough warming aloft causes some rain to mix in with the snow/sleet and with temperatures at or below freezing, any rain that does fall can freeze on many surfaces. In fact, temperatures will be reluctant to climb above freezing for most of the morning on Thursday in the NYC metro area; especially, across the normally colder N/W suburbs...plain rain is likely by the afternoon on Thursday.

A very similar scenario may unfold for the weekend in the Mid-Atlantic region in that snow, sleet and/or freezing rain is on the table…much like the upcoming mid-week event. Map courtesy NOAA, tropicaltidbits.com

Similar scenario possible this weekend with a mixture of snow, sleet, freezing rain and rain

Looking ahead, there have been rather persistent storm signals for a system this coming weekend that can have an impact on the Mid-Atlantic in much the same manner as the mid-week event in that frozen precipitation will be possible on the front-end and then plain rain is likely on the back end. In fact, the setup will be quite similar with a late week cold frontal passage and then a fresh cold air mass pushes into the region by the early weekend as moisture gathers to the southwest of here. As a result, there can be some snow, sleet and/or freezing rain from later Saturday into Saturday night and the frozen precipitation will likely change to plain rain on the back end of the storm system early Sunday.

Looking ahead to next week, there are signs for a storm system to head towards the Mid-Atlantic coastline potentially resulting in some accumulating snow from later Tuesday into Wednesday. As with this week’s system, snow can certainly be mixed with sleet and/or freezing rain in some sections…way too early for details. Map courtesy ECMWF, Weather Bell Analytics

Snow threat by the middle of next week and it may be significant

After the weekend system passes by to the northeast of here, cold air is likely to push into the Mid-Atlantic region and, as many teleconnection indices suggest, this cold air intrusion may be able to penetrate farther to the south than prior ones during the next few days. It appears that yet another storm system may gather strength by the middle of next week in this ongoing active weather pattern and this one is likely to have more cold air to work with...all of which enhances the chance for accumulating snow in the Mid-Atlantic region perhaps in the Tuesday/Wednesday time frame and it may be significant. Stay tuned...many days to go before next week’s threat.

Meteorologist Paul Dorian
Arcfield
arcfieldweather.com

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