GSP
LONG TERM /FRIDAY THROUGH MONDAY/...
As of 300 am EST Tuesday: Friday will provide a brief lull between
systems as a shallow
ridge sets up between a departing
shortwave
trough and the next major system amplifying over the northern
Plains. We are trying to keep our excitement in check for the
weekend system given the spread evident in the operational models
and
ensembles. Uncertainty remains high, but there are trends toward
greater confidence in at least some wintry weather affecting much of
our region over the weekend.
The setup will include a zonally-oriented 850
mb baroclinic zone
atop our region just north of the old frontal zone Friday night.
This could well provide a focus for moist upglide redeveloping
quickly across the area Friday night into Saturday. Subfreezing 850
mb temps would permit wintry ptypes at onset in most areas, with
mainly snow in the northern tier and possibly a light wintry mix
farther south as profiles wet bulb down. Meanwhile, the
deepening
upstream system will dive southeast through the central
CONUS the
first half of the weekend and amplify west of the Appalachians. Run-
to-run and model-to-model consistency issues abound, with the
operational
GFS now much deeper with an
H5 low tracking across the
Deep South Saturday night. The
ECMWF and Canadian camps depict more
of a positively-tilted open wave crossing the forecast area. The
common factors include fairly cold profiles already in place and
decent potential for
moisture return ahead of the amplifying system.
The main difference is that the
ECMWF/CMC solutions would be a
quicker hit/shorter duration, which would limit wintry accumulations
a bit more.
The
GFS, on the other hand, exhibits a far more dynamic southern
closed low position, bringing the heart of its
moisture and forcing
over the cold air in place Saturday night through Sunday. In fact,
the 850
mb low center track on the
GFS is perfect for record setting
snowfalls across our region. This solution has the surface low
tracking through southern AL/GA along the frontal zone Saturday
night and
deepening over the SC
coastal waters on Sunday. In
addition,
frontogenesis would be robust atop our area in this case,
and a lobe of negative
EPV crossing the region would even suggest
some potential for thundersnow. However, it`s important to note the
recent consistency issues with the
GFS runs, and the fact that the
GEFS plumes have plenty of spread. Still, the prudent course is to
to start featuring the system in the HWO given the potential for
accumulating snowfall.
The upper system will depart late Sunday, but with lingering
northwest
flow snowfall quite possible along the spine of the
southern Appalachians. Additional
height falls may occur back to the
west over the Ohio River Valley on Monday. This early week system
appears a bit more
moisture starved, and it seems the better
dynamics will pass north of our forecast area. However, additional
scattered snow showers will be possible in the mountains following
the wave passage late Monday given the northwest
flow upslope
moisture in the residual cold air.