Area Forecast Discussion

Pittsburgh, PA

Forecast Discussion for PBZ NWS Office
FXUS61 KPBZ 011807

Area Forecast Discussion
National Weather Service Pittsburgh PA
107 PM EST Tue Dec 1 2020

Area snow will begin to taper off tonight into Wednesday morning
before dry weather returns Wednesday afternoon under building high
pressure. Seasonable temperature and dry weather should continue
until a late week system.


Snow will generally continue overnight as moisture wraps around an
upper low tracking into southeastern Canada. An embedded shortwave
will give one last southward push of snow this evening, potentially
aiding in heavy snow band development along the I-80 corridor.
During this last push, strong upper jet dynamics, steepening low
level lapse rates and enough dendritic growth will promote an
additional 1-2" of snow across eastern OH and southwestern PA while
northwestern PA and the eastern ridge tops could see another 3-6" of
snow. Thus, the Winter Storm Warnings and Winter Weather Advisories
will continue.

Drier air will begin infiltrating the region tonight as the upper low
further pulls to the northeast. The drier air combined with weakening
NW flow and the early stages of building sfc high pressure will
reduce snowfall rates and erode showers from the southwest to the
northeast. Weak lake enhancement may maintain snowfall rates north of
I-80 later into the night, which could boost area snowfall totals.


Building surface high pressure and rising pressure heights will
continue to eliminate snow showers Wednesday, which will linger
longest over the eastern ridges and I-80 corridor. By the afternoon,
dry weather should develop for all locations, with increasing
insolation expected. Residual cold air and snow covered grounds will
limit heating and keep area temperature below seasonal averages.

Dry weather with slight warm advection is expected for Thursday as
shortwave ridging develops aloft ahead of a developing shortwave
trough over the Mississippi River Valley. Despite increasing cirrus,
area temperature should rise to near seasonal averages.


Much uncertainty remains in the long term forecast period as models
depict a wide array of solutions for how the aforementioned trough
develops. Among the solutions, one path has the low significantly
deepening and becoming occluded as it tracks across the Ohio River
Valley into the Mid-Atlantic, which would promote widespread rain
through the weekend within the warm sector over the area,
transitioning to snow on the back side. The other keeps the trough an
open wave, swiftly crossing the region Friday with minimal
precipitation impacts. Forecast represents a blend of these outcomes,
keeping low chance PoPs and near normal temperature through the

The pattern will likely remain unsettled with another low pressure
system bringing additional precipitation early next week.


Cold air spinning into the region around low pressure moving into
western New York will continue to provide snow into tonight across
the region. Frequent drops to IFR/LIFR visibility can be expected,
especially from PIT on north and east. FKL/DUJ will see the most
restrictions due to lake enhancement. Ceilings have improved a bit to
MVFR in many cases as increased mixing has raised inversion heights
a bit, but this will come with the price of gustier wind, as well as
more variable visibility conditions as snow becomes more showery.
Some overall improvement is expected late tonight as the low starts
to pull away, and VFR conditions may return to most locations south
of I-80 by midday tomorrow.

Restrictions will continue to east Wednesday afternoon as the low
pressure system lifts into eastern Canada, with high pressure
building in its wake. The next chance of general restrictions may
arrive this weekend.


PA...Winter Weather Advisory until 7 AM EST Wednesday for PAZ009-013>016-
     Winter Storm Warning until 7 AM EST Wednesday for PAZ007-008-074-
OH...Winter Weather Advisory until 7 AM EST Wednesday for OHZ039>041-
WV...Winter Weather Advisory until 7 AM EST Wednesday for WVZ001>004-012-
     Winter Storm Warning until 7 AM EST Wednesday for WVZ510>514.



NWS PBZ Office Area Forecast Discussion