11:30 AM (Mon) | ***Wintry mess on the way for the Mid-Atlantic with snow, sleet, and freezing rain… slick spots possible and small accumulations…watch for burst of heavier snow in DC region***

“Evaporative cooling” at the arrival time of the precipitation in the DC metro region late today could cause a quick drop of temperatures by a few degrees. As a result, the initial wave of mixed precipitation could actually change to all snow for awhile by early this evening in the DC metro region and there can even be a burst of heavier snow. Map courtesy NOAA, tropicaltidbits.com

Overview

A wintry mess of snow, sleet, freezing rain, and plain rain is coming to the Mid-Atlantic region as low pressure heads from the south-central states to the Ohio Valley.  A dense dry and cold air mass is in place across the Mid-Atlantic region and it will be reluctant to give up its ground as moisture pushes in this direction from the west-to-southwest.  As a result, frozen precipitation is a good bet during this event in the entire DC-to-Philly-to-NYC corridor and the progression of the moisture field to the northeast will be quite slow.  The arrival time in the DC metro region should be 4 or 5 pm and there is the threat for a burst of heavier snow by early tonight - an hour or two after the onset of the mixed precipitation. Arrival time in the Philly area is late this evening and precipitation will probably hold off until tomorrow morning for the NYC metro region.

Looking ahead, the active weather pattern will continue and another storm is going to intensify near the Carolina coastline Wednesday night/Thursday and its impact in the DC-to-Philly-to-NYC corridor is likely to be limited.  Yet another storm could travel across the country this weekend and perhaps have an impact in the Mid-Atlantic region in the Sunday/Monday time frame. 

A mix of light snow, sleet and freezing rain is likely on Tuesday and Tuesday night in areas north of the PA/MD border…watch for slick spots on untreated surfaces. Map courtesy NOAA, tropicaltidbits.com

Discussion

The new work week begins with high pressure across the Northeast US and cold, dry dense air is in place along the DC-to-Philly-to-NYC corridor. Meanwhile, low pressure is beginning to make a move from the central Plains to the Ohio Valley and it currently has a ton of moisture with it which is about to push into the cold, dry air mass entrenched across the Mid-Atlantic.  As the moisture field pushes into the dry air mass in the Mid-Atlantic region later today and tonight, it will tend to hold together pretty well in the DC metro region, but it will tend to break apart some by the time it reaches areas to the north of the PA/MD border.  Consequently, a better chance of heavier bursts of precipitation will take place in the DC metro region during this event (by early tonight) as compared with areas north of the PA/MD border on Tuesday/Tuesday night. 

Freezing rain will be a concern in the Mid-Atlantic region during this upcoming wintry mess of an event as temperatures will hover near or below freezing much of the time. Map courtesy Weather Bell Analytics, NOAA

DC metro region

A wintry mix of snow, sleet and rain is likely to arrive in the DC metro region around 4 or 5 pm moving from southwest-to-northeast.  With the cold, dry air mass in place, there can be “evaporative cooling” at the onset of the precipitation which could result in a quick drop in temperatures of a few degrees and this could result in a changeover from mixed precipitation to all snow for awhile throughout the DC metro region.  In fact, there is the chance for a burst of heavier snow by early tonight which can quickly cause poor visibility and slick spots on roadways.  The chances for snow in the DC metro region will diminish later tonight, but there can be sleet and freezing rain at times; especially, in areas to the north and west of the District which can cause additional slick spots on untreated surfaces.  Precipitation winds down Tuesday morning in the form of freezing rain early in the AM and plain rain later in the morning.  Accumulations of anywhere from a coating to as much 3 inches or so are possible during this event given the threat of a burst of heavier snow…watch for slick spots during any snow bursts this evening and also late tonight/early Tuesday with the likelihood of freezing rain and/or sleet.

Philly metro region

The push to the north and east of the moisture field with this system will be inhibited by the dense dry air mass that is entrenched across the northern Mid-Atlantic.  As a result, snow may not arrive in the southeastern part of PA until late this evening and it could take an unusually long time for it to move from southern Chester County (late evening arrival) to Bucks County (after midnight arrival).  Occasional light snow, sleet and freezing rain will continue from late tonight through tomorrow night and there can be slick spots on untreated surfaces and accumulations of a coating to an inch or two. 

New York City region

The dense dry air mass in pace across the NE US will help to push off the arrival of the precipitation until tomorrow morning in the NYC metro region.  There will be occasional light snow, sleet and freezing rain on Tuesday and Tuesday night and even into the early morning hours of Wednesday with slick spots possible on untreated surfaces and accumulations of a coating to an inch or so are possible. 

Low pressure will intensify near the Carolina coastline late Wednesday night/Thursday and its precipitation shield is likely to generally stay to the south and east of the DC-to-Philly-to-NYC corridor…it does still need to be closely monitored as a small shift could make a big difference. Another system will come ashore in California late this week (left circle) and this could pose a winter storm threat to the Mid-Atlantic region by the latter part of the upcoming weekend. Map courtesy NOAA, tropicatidbits.com

Late week storm and late weekend storm threat

Another low pressure system will move across the central US later this week and it’ll likely intensity over the Carolina coastline late Wednesday night/early Thursday.  The precipitation shield for this system looks like it will generally be confined to the region south and east of the DC-to-Philly-to-NYC from southern West Virginia/southern Virginia to the Carolinas.  It is still a close call for the Mid-Atlantic and will need to be monitored over the next couple of days. 

Here we go again…12Z Euro model depicts a powerful-looking storm system near the Mid-Atlantic coastline as of Monday evening, February 1st. Map courtesy WSI, Inc., ECMWF

Another system will impact California later this week and it could end up in the eastern states by the latter part of the upcoming weekend.  The threat of snow to the Mid-Atlantic region from this next in a series of storms would likely be in the Sunday/Monday time frame. Of course, snow lovers in the Mid-Atlantic region must now feel like Charlie Brown with the football being pulled away from him as he is about to kick it.

As the overall active weather pattern produces storm-after-storm in California in coming days, snowfall amounts could become amazing in some higher elevation locations. In fact, model forecasts suggest as much as 12+ feet of snow in the Sierra Nevada Mountains of eastern California over the next ten days or so. Map courtesy NOAA, tropical tidbits.com

Incredible snow for Sierra Nevada Mountains in eastern California

One final note of interest, this active weather pattern is bringing storm-after-storm through California which has certainly alleviated their drought conditions of recent weeks.  Significant rainfall is likely to continue in coastal sections during this active stretch of weather and tremendous snowfall is likely in the higher elevation locations of the Sierra Nevada Mountains in eastern California.  In fact, one computer forecast model puts out as much as 12 feet of snow in the Sierra Nevada Mountains over the next ten days. This likelihood of heavy rain and snow is actually some good news for the state of California as the snowpack in the Sierra Mountains is critical to water supply during the summer season (i.e., snow melt).

Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com

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