SUMMARY...Moderate to heavy snow now developing across parts of
central Virginia and Maryland is expected to persist through mid to
late morning, with rates (around or in excess of 1 inch per hour)
likely maximizing in the 6-10 AM EST time frame.
DISCUSSION...A broadly cyclonic 50-70+ kt 500 mb jet streak
continues to gradually develop eastward across the northern Gulf
Coast states, with its exit region now beginning to nose to the lee
of the southern Appalachians, toward the southern Mid Atlantic coast
through mid to late morning. It appears an associated broad area of
strong upward vertical motion will include a period of strengthening
lower/mid-tropospheric frontogenesis across Virginia and adjacent
portions of the Mid Atlantic.
Across central Virginia into adjacent portions of central Maryland,
where temperature profiles are expected to remain entirely below
freezing, models indicate that lift may begin to become maximized
within the favorable mixed-phase layer for dendritic ice crystal
growth by daybreak, and continue through mid to late morning. Aided
by relatively high precipitable water content (up to around .70
inches), one or more bands of heavy snow, at rates around or in
excess of 1 inch per hour, appear possible. Forecast soundings
suggest that this may persist for a 3-4 hour period at any
particular location, generally in a narrow corridor from the
vicinity of the Blue Ridge, north of Roanoke VA, east/northeastward
through southern portions of the Greater Washington D.C./Baltimore
Metropolitan Area.