Here we go again for the Mid-Atlantic I-95 corridor region with more accumulating snow on the way. A temperature gradient boundary zone that has been hanging around the eastern states for several days will again act as a conduit for moisture later tonight and Tuesday. This next batch of moisture will move in a southwest-to-northeast fashion reaching the Mid-Atlantic region early tomorrow. Tomorrow’s event should be primarily, if not completely, in the form of snow in Philly and NYC, but there is a chance that the precipitation begins as sleet in the DC metro region before quickly changing to all snow. Precipitation should break out near or just before daybreak in the DC metro region and then in the early-to-mid morning hours across Philly and NYC. This will be a “fast-moving, quick thumping” type of snowfall with a burst of heavy snow in DC during the morning hours, and in the late morning/mid-day hours in Philly and NYC. The snow should then end quickly from northwest-to-southeast by early tomorrow night.
The upper level pattern for this upcoming event is rather impressive with a strong jet streak playing a key role. It appears that the I-95 corridor region will be in the right/rear quadrant region of a strong upper level jet streak which is conducive to upward motion. Snow accumulations should be on average in the 3-6 inch range from DC-to-Philly, and 2-4 inches in the New York City metro region. We’ll have to see if any small-scale heavier snow bands set up on Tuesday which is quite possible given the expected strong dynamics associated with this powerful upper level jet streak. [12Z NAM 300 millibar winds forecast map for early Tuesday depicting the strong upper level jet streak at 150+ knots across the Northeast US (purple region)].
A few notes about yesterday's snowfall in Philly...Philly Int’l Airport officially recorded 8.6 inches which was only the 8th time in which 8 inches or more has fallen in the month of December and 3 of those 8 events have occurred in just the last 5 years. Also, yesterday's 8.6 inches of snow at PHL was more than recorded for the entire 2012-2013 winter season.
Finally, another storm threatens the Mid-Atlantic region this weekend with more significant snow and/or rain possible.