Latest NWS Sterling discussion good writeup:
By Wednesday morning, an upper level trough will be digging south
and east across the Mississippi River Valley, taking aim toward the
TN/OH Valley`s. The aforementioned area of low pressure is progged
to consolidate over the eastern Carolinas Wednesday afternoon,
strengthening as it tracks along or just east of the Delmarva
Peninsula Wednesday night. At the same time, the upper trough will
take on a negative tilt as it approaches the Ohio Valley late
Wednesday and the right entrance of the jet positions itself nicely
in terms of upward motion and divergence aloft centering over the
CWA.
Precipitation associated with the system will overspread the area
Wednesday morning, a touch slower with the latest model runs, while
much of the area is at or below freezing. This will allow for snow
to the be the favored ptype initially. The model trends with the
high over or near Quebec have been stronger, helping to supply the
colder air on the eastern slopes of the mountains. Thereafter,
guidance wants to allow for warmer air to work its way along and
east of the I-95 corridor to produce a rain/snow mix Wednesday
afternoon and evening. Further north and west, thermal profiles
indicate an all snow event, with accumulating snow looking
increasingly likely. Model ensembles support this as well, with
fairly good agreement across the board, and probabilities of
exceeding 1/3/6" all increasing run to run.
At this time, an enhanced winter storm threat exists Wednesday and
Wednesday night along and west of the Blue Ridge Mountains,
potentially resulting in a disruption to travel, while a slight
winter storm threat along and east of the I-95 corridor. With a
touch slower progression of the system, models linger precipitation
into a good portion of Wednesday night as the low pushes away from
the coast Thursday morning. There is some discrepancy in this
progression between the global guidance, so this will have to be
ironed out in the coming days. Confidence is increasing with the
potential for accumulating snow and potential impact to the area,
but exact amounts and placement of the rain/snow line carries a
lower confidence at this time. Follow our latest forecast on this
system and potential impacts at weather.gov/lwx/winter.
