1:05 PM | *Snow threat for Thursday night and Friday*

Overview
The weather will be quite interesting this week with big changes coming to the Mid-Atlantic region around mid-week.  The week is starting off quite mild with temperatures way above normal for this time of year and that mild weather will continue on Tuesday as well.  By late tomorrow night, rain is likely to move into the I-95 corridor as a strong cold front approaches and that rain threat continues for the first half of Wednesday.  Much colder air will pour in behind the mid-week frontal passage and then we’ll have to monitor a potential storm that should form near the Mid-Atlantic coastline on Friday.  As a result of the influx of cold air and late week storm potential, snow is a threat in the DC, Philly, and New York City corridor from later Thursday night into Friday.

Mid-week rain
A strong cold front approaches by mid-week and it will generate occasional rain in the I-95 corridor from late tomorrow night into mid-day on Wednesday.  The rain can come down hard at times as a strong cold front pushes through the region and there can be some gusty winds and a thunderstorm or two.  Temperatures will fall noticeably following the frontal passage as early as Wednesday afternoon and it’ll be quite cold again around here for Wednesday night and Thursday.  

12Z GFS forecast map for Friday afternoon (blue=snow, green=rain); map courtesy tropicaltidbits.com, NOAA

Snow threat Thursday night and Friday
By Thursday night, clouds will start to increase as moisture pushes eastward across the Ohio Valley.  One low pressure system is likely to track into the Ohio Valley Thursday night, and then weaken and a new low pressure area is likely to form early Friday near the Mid-Atlantic coastline.  This low will then intensify during the day on Friday as it pulls northeastward from the Mid-Atlantic coastline.  As a result, snow could break out in the DC, Philly, and New York City corridor later Thursday night and continue into Friday with temperatures likely cold enough to support precipitation in the form of snow along the immediate I-95 corridor. Two questions remain at this point which make it difficult to have any confident handle on potential accumulations, if any, during the late week time period.  The open questions are:  1) “how quickly can this system intensify and 2) "how far up the coast can it travel before pulling out to sea? Currently, NOAA’s GFS (above) and GFSX computer forecast models tend to agree with the European model in forming a relatively weak and somewhat suppressed (i.e., well to the southeast of here) storm system which would limit the potential for any serious accumulating snow around here; however, there are still reasons to believe that a stronger storm can form and move farther up the coastline and other forecast models support that more ominous possibility (e.g., Canadian GEM, see map below).  Stay tuned.  

12Z Canadian GEM forecast map for Friday afternoon (blue=snow, green=rain); map courtesy tropicaltidbits.com

Longer term temperature swings
Relatively cold conditions are likely during the upcoming weekend following the possible late week storm and there is even a chance for more snow in parts of the Mid-Atlantic region from a southeastward moving “clipper” low pressure system.  Beyond that, there are signs for a significant warm up for much of next week before it likely turns colder again by the middle of the month. 

Meteorologist Paul Dorian
Vencore, Inc.