Area Forecast Discussion
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FXUS61 KPBZ 250418

Area Forecast Discussion
National Weather Service Pittsburgh PA
1118 PM EST Mon Feb 24 2020

Periodic rain is expected through Wednesday with crossing low
pressure. Colder weather and snow showers are then expected to end
the week.


Rain should continue to overspread the region overnight as a lead
shortwave and moist advection in SW flow aloft approach and cross the
region. The onset of the rain should initially be delayed with dry
air in place, though with the moist advection and shortwave support
rain should fall after saturation occurs.


A brief break in the rain is expected Tuesday morning as the
shortwave support exits to the north. Showers will return early
Tuesday afternoon with the passage of a warm front. Mid and upper
level dry air will filter in from the south late Tuesday and quiet
cloudy weather will prevail.

A deepening Central CONUS trough is expected to track east Tuesday
night and Wednesday as the sfc low crosses the Upper OH Valley/Lower
Great Lakes region. Another period of rain is expected Wednesday
morning and continue into the evening as this trough, and its
associated sfc cold front, cross the region. Precipitation rates may
be heavy east of Pittsburgh at times due to strong frontogenesis.
Wind gusts may reach advisory criteria in the ridges due to
isallobaric acceleration and a strong gradient wind Wednesday night
into Thursday. The trough is progged to phase with a nrn stream
trough Wednesday night as it deepens across the NE CONUS, with rain
showers changing to snow showers behind the cold front. Above average
temperatures are expected to return to seasonably cold levels by
Wednesday night after FROPA.


Upper troughing is progged to persist across much of the Eastern
CONUS through Saturday. Shortwaves rotating through the main trough,
with lake/terrain enhancement, should maintain periodic snow showers
into the weekend. Model soundings highlight Thursday and Friday
afternoon for having the best ingredients for producing moderate to
heavy snow bands. High northeast wind gusts from a lingering gradient
wind, steep lapse rates from strong cold advection, and deep residual
moisture from the upper-level low over the northern Great Lakes
create a favorable environment for bands over Western PA. However,
low-level direction wind shear (from the sfc to 700mb) and any shift
from NW flow have a chance to disrupt this pattern.

A Central CONUS ridge should track east by Sunday, returning dry
weather to the region. Colder than average temperatures are expected
through the period.


VFR conditions will great the evening forecast, with a slow decay to
MVFR restrictions from west to east. ZZV will see this reduction
first, with the lower clouds reaching PIT around midnight. Initially,
do not expect much restrictions for vis, as the rain will be
encountering a very dry atmosphere. ZZV will be the exception to
this, as current forecast soundings are showing them dipping into IFR
cigs and MVFR vis restrictions shortly after midnight. Widespread
MVFR is expected through Tuesday, with the best chance for more
significant rainfall in the afternoon.

Sub VFR weather continues through Wednesday. The next weather system
brings MVFR and IFR weather in snow showers Thursday. IFR weather
could continue into Friday morning especially for FKL and DUJ as
lake enhanced showers persist.




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