Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pittsburgh PA
831 PM EDT Sat Mar 15 2014
low pressure crossing south of the region may bring some snow late
Sunday and Monday.
Near term /through Sunday/...
only late evening changes needed for the near term period were adjustments
to sky and temperature trends.
models continue to struggle with the evolution of the next system
prognosticated to cross south of the region late Sunday. The GFS
maintains the strongest and most northerly solution while the
other models keep the bulk of the precipitation well to the south.
Regardless...there seems to be a sharp cutoff in the precipitation
north of the Mason Dixon line with high pressure remaining
situated over the Great Lakes and helping to suppress this system.
As such...have maintained the highest snow totals south over the
ridges and maintained smaller accumulations elsewhere.
All of the models continue to suggest to at least some modest
accumulations over the ridges. Since the two systems are just
beginning to interact with one another this afternoon...felt best
to carry a Winter Storm Watch for the ridge counties for now.
Current thinking would hedge towards the highest amounts being
limited to Tucker County but with the continued model
uncertainty...felt a watch was the best choice for all three
counties for now.
Short term /Sunday night through Tuesday/...
precipitation will be ongoing for the first half of the period as
the low pressure system over the south heads towards the coast.
Considering the system remains an open wave...precipitation should
quickly depart by midday Monday. Further north and
west...skies should begin to clear out...and it should be a decent
day from Pittsburgh northward. However...with the northeasterly
flow...temperatures will most likely stay below or just near
High pressure will build over the remainder of the region by
Monday night. Warm advection Tuesday should bring temperatures
once again into the 40's and 50's.
Long term /Tuesday night through Saturday/...
another deep upper low is forecast to move from the Central
Plains and over the Great Lakes by Wednesday. The preponderance
of model guidance continues to indicate the upper low should take
on an increasingly negative tilt with a strong middle-level jet
rounding the base of the upper low...with resultant impressive
0-6 km shear. However...given the strong warm advection indicated
above the boundary layer...prognosticated instability is lacking and
thunder should be precluded.
After the passage of wednesday's system...global guidance becomes
increasingly divergent in its approach to handling the short wave
pattern. However...increasing heights signal warm advection...hence
temperatures are expected to moderate shortly after the Wednesday
Aviation /01z Sunday through Thursday/...
broken-overcast low clouds moving out of north. Some scattered-broken middle clouds to
replace them this evening. The southern half will be clear to scattered middle
clouds. West winds of 10-15 kts should taper a bit this evening and
start to veer. Middle level clouds will be on the increase Sunday as
the next system begins its journey across far southern part of forecast area.
Outlook.../Sunday night through Thursday/...
the next chance for restrictions will come from the northern edge of
low pressure that should cross from the Gulf Coast to the coast of
North Carolina. IFR conditions in snow are possible Sunday night into
Monday morning at mgw/lbe...with lesser chances at zzv/hlg/pit/agc.
VFR conditions are expected behind the system Monday through Tuesday
night. Another system should bring showers and possible restrictions
Wednesday...with a return to VFR Wednesday night and Thursday.
Maryland...Winter Storm Watch from Sunday afternoon through Monday
afternoon for mdz001.
WV...Winter Storm Watch from Sunday afternoon through Monday
afternoon for wvz023-041.