Mesoscale Discussion #291 JUST Issued

Mesoscale Discussion 0291
NWS Storm Prediction Center Norman OK
0901 PM CDT Mon Mar 13 2017

Areas affected…Northern VA…Central MD…Southeast PA…Western

Concerning…Heavy snow

Valid 140201Z – 140600Z

SUMMARY…Moderate to heavy snow will blossom across this region
during the evening hours, with rates of over 1″/hour possible
through 06z.

DISCUSSION…Recent radar loop indicates that precipitation is
rapidly increasing in areal coverage and intensity across parts of
the Delmarva region. At 01z, snow is being reported along and north
of a line from NYG – NAK – PTW, while rain is being reported to the
south. This rain/snow line will likely move only slightly northward
before 06z, suggesting that the DC and Baltimore metro areas will
remain in mostly frozen precipitation. However, several recent
model runs suggest that this southern fringe of the snow zone may
begin to mix with/change to sleet or freezing rain around midnight
as profiles begin to warm in the 900-700mb layer. Nevertheless, it
appears likely that a corridor of locally heavy snowfall rates will
develop from far northern VA, northeastward into central MD and
southeast PA through 06z. Warm surface temperatures may result in
substantial melting of snow initially, but higher rates will likely
overcome the warm ground and begin to accumulate soon.


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