11:30 AM (Wed) | ***Significant winter storm to bring accumulating snow/ice to the Mid-Atlantic region from tomorrow into Friday…several inches on the tables in DC-to-Philly-to-NYC corridor***
Paul Dorian
A strong jet streak aloft (250 millibars) will contribute to upward motion in the Mid-Atlantic coastal region on Thursday and Thursday night and this will lead to development and intensification of surface low pressure. Map courtesy NOAA, tropicaltidbits.com
Overview
A significant winter storm will impact the Mid-Atlantic region on Thursday and Thursday night and it is likely to develop into a rather long duration event and last well into the day on Friday. Snow should break out early tomorrow morning in the DC and Philly metro areas and by the late morning hours in New York City. The snow can come down hard for a few hours beginning shortly after its arrival time in the I-95 corridor. The precipitation may slacken off for a brief time later tomorrow into early tomorrow night, but more precipitation will re-develop tomorrow night likely as a wintry mix and this can change back to all snow on Friday.
12Z NAM surface forecast map as of 7AM, Thursday with widespread snow (shown in blue) in the Mid-Atlantic region and it can come down hard for awhile. Map courtesy NOAA, tropicaltidbits.com
Details
The winds kicked up early last night in the Mid-Atlantic region following the passage of a strong cold front and temperatures (and dew points) dropped dramatically in the overnight hours. Strong high pressure will build today across northern New England/southeastern Canada and then act as an anchor for this fresh, cold, dense air mass as moisture pushes heads this way from southwest-to-northeast. Temperatures are quite likely to stay at or below freezing during much of this upcoming event in the I-95 corridor which will ensure plenty of frozen precipitation or the freezing of liquid precipitation on trees and untreated surfaces – even in the metro regions.
12Z NAM forecast map of “frontogenesis” as of 7AM Thursday and this can lead to some heavy snow bands along the I-95 corridor in the morning and mid-day hours. Map courtesy NOAA, tropicaltidbits.com
Unlike the storm from earlier this week which moved into the Ohio Valley, this upcoming low pressure system will end up just off the Mid-Atlantic coastline allowing for a colder environment in the region. Snow should break out in the early morning hours across DC and Philly and by the late morning hours in New York City. With some expected strong lifting action in the atmosphere, the snow can come down pretty hard for a few hours beginning shortly after its arrival time and this stretch of accumulating snow may actually turn out to be the heaviest snowfall during this event in some locations. There is a chance the precipitation slackens off a bit for a brief time late tomorrow or early tomorrow night, but it will re-develop likely as a wintry mix of snow, sleet and/or freezing rain.
Temperatures will remain at or below freezing throughout much of the upcoming event and icing will become a big problem in parts of the I-95 corridor. This is a forecast map of “total accumulated freezing rain” through mid-day on Friday by the 12Z GFS. Map courtesy NOAA, Pivotal Weather
The low pressure system will tend to stall out for awhile just off the Mid-Atlantic coastline and this will allow for a rather long duration event. A wintry mix on Thursday night may end up lasting well into the day on Friday in the I-95 corridor and it can conceivably change back to all snow with some additional accumulations possible. Snow arrival times and accumulation estimates for the metro regions along I-95 are listed below. The higher amounts in those snowfall ranges will be on the N/W side of the given metro region and there can be isolated higher amounts.
DC: 3-7AM; 3-6 inches of snow with an icy buildup possible
Philly: 4-8AM; 4-8 inches with an icy buildup possible
NYC: 10AM-1PM; 4-8 inches
Meteorologist Paul Dorian
Perspecta, Inc.
perspectaweather.com
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