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ACUS11 KWNS 081952
SPC MCD 081952

Mesoscale Discussion 1789
NWS Storm Prediction Center Norman OK
0152 PM CST Fri Dec 08 2017

Areas affected...Parts of southern/eastern Virginia into the
Delmarva Peninsula

Concerning...Heavy snow

Valid 081952Z - 090045Z

SUMMARY...Heavy snow rates around or in excess of 1 inch per hour
could develop and impact Richmond and surrounding areas of southern
and eastern Virginia by early evening.  This could commence as early
as 5 PM EST and continue through the 8-9 PM EST time frame.

DISCUSSION...Strengthening large-scale ascent is contributing to
increasingly saturated thermodynamic profiles and precipitation
rates across much of southern through eastern Virginia.  This
appears likely to be aided by a zone of enhanced lift associated
with mid-level frontogenetic forcing, which is forecast to redevelop
northeast of the central Appalachians through the northern Mid
Atlantic Coast region by early this evening.  This is expected to
increase lift through the favorable mixed-phase layer for large
dendritic ice crystal growth, which could potentially provide
support for heavy snow rates.

Generally west through north of the Hampton Roads area, roughly from
near Danville through much of the Greater Richmond area,
northeastward into the Delmarva Peninsula, models suggest that
temperature profiles are generally below freezing.  Current surface
temperatures/wet-bulb temperatures appear marginal for snow reaching
the surface.  However, with the onset of nightfall, and  perhaps
weak low-level cold advection and cooling associated with melting
precipitation, a changeover to snow appears possible by the 22-23z
time frame, if not before.  Heavy snow rates around or in excess of
1 inch per hour appear possible, and may continue into the 01-03Z
time frame, before diminishing.

..Kerr.. 12/08/2017

...Please see for graphic product...


LAT...LON   36807940 37537853 38057728 38907564 38747491 37727568
            36887751 36447929 36807940 is the U.S. government's official web portal to all federal, state and local government web resources and services.