Area Forecast Discussion
Issued by NWS Pittsburgh, PA

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FXUS61 KPBZ 271320

Area Forecast Discussion
National Weather Service Pittsburgh PA
920 AM EDT Tue Oct 27 2020

Light rain chances will continue today with a weak crossing
disturbance. Widespread rain is expected Thursday and Thursday night
with low pressure.


A rather dreary and stagnant pattern continues across the forecast
area. Adjusted temperatures just a degree cooler to account for the
persistent cloud cover. Light rain chances continuing to be
intermittant through this afternoon and evening will leave a slight
to chance of measurable precip. Temperatures continue to be 5 to 10
degrees below normal.


The last in a series of weak crossing shortwaves, and limited jet
ascent, should maintain the patchy light rain chances tonight. Weak
sfc high pressure is expected to briefly build across the Upper Ohio
Valley region Wednesday, with dry weather expected.

A closed upper low is progged to advance out of the Southern Plains
Wednesday night and Thursday, as remnant tropical low tracks NE from
the Gulf in SW flow ahead of the upper low. The upper low is then
expected to phase with a northern stream trough later Thursday and
Thursday night as it crosses the Ern CONUS, as the associated sfc low
tracks across the Ohio Valley/Mid Atlantic region. The combination
of the remnant tropical moisture, and increasing jet and shortwave
supported ascent, should result in widespread rain across the region
late Wednesday night through Thursday night. At this time, total QPF
amounts of 1.5 to 2.5 inches are expected over a 36 hour period.
With relatively dry antecedent conditions in place, these amounts
should not result in any major hydro issues, though future trends
will continue to be monitored.

The sfc low is progged to track to the Mid Atlantic Coast Thursday
night. Cold advection behind the low could result in some of the rain
mixing with snow north of I 80 late Thursday night, though no
accumulation is expected. Seasonably cool temperatures are expected
through the period.


The upper trough should complete its passage Friday, with rain
chances diminishing. Dry weather should return Friday night through Saturday
night as high pressure builds across the region ahead of a Central
CONUS trough. The trough is then expected to cross the region Sunday
with low chances for showers. Sfc high pressure building under NW
flow aloft should return dry and cool weather for Monday.


MVFR stratus is expected for much of the day due to saturated low
levels within a somewhat stagnant flow. However, slight sfc high
pressure building and increasing lift ahead of an approaching
shortwave trough should lift area cigs and could potentially create
brief breaks in the low level deck.

The passage of the shortwave trough will create areas of light
rain/drizzle late today through the overnight period, favoring the
I-80 corridor. In addition, top-down moistening plus weak frontal
convergence will drop area restrictions overnight, with widespread
IFR/LIFR cigs expected.

Building sfc high pressure, weak shortwave ridging, and slight dry
air intrusion will all help area restrictions improve through the day

Widespread restrictions amid light to moderate rainfall is expected
Thursday into early Friday morning as tropical remnants pass
southeast of the region.

VFR conditions should return by Saturday with building sfc high
pressure and shortwave ridging.




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