FXUS61 KPBZ 090120

Area Forecast Discussion
National Weather Service Pittsburgh PA
920 PM EDT Wed Jul 8 2020

The pattern of hot and humid weather with scattered afternoon and
evening thunderstorms will persist through Friday. A weak cold front
will increase rain chance for the weekend.


Outflows from convection this evening over the ridges has indeed
allowed some small showers and storms to develop into western PA just
east of the city. These cells have weakened and are now dissipating.
The forecast area will become precip free within the next hour or

Tonight, any isolated showers and thunderstorms will come to an end
by or just after 8pm with the loss of the daytime heating and no
synoptic forcing to assist. Mainly any locations that already
received rain will see fog development tonight but given the amount
of moisture available with dewpoints in the upper 60s, fog is
possible across alot of the area tonight.

During the day on Thursday, the lack of cloud cover early in the day
will assist in warming temps through the morning. Ample moisture in
place will yield some lower 70s degree dewpoints. Locations that do
not see any convection or a shower or thunderstorm will see Heat
Index values cross the 100 degree mark in many locations. Thus, have
issued a Heat Advisory for Thursday afternoon and evening.


Ridging will still be in place but slightly weaker over Ohio zones
where chance afternoon PoPs were maintained...with slight/isolated
elsewhere. Chances will increase Friday and Saturday with the
approach/passage of an upper trough and associated surface front.

Well above normal temperatures will continue Thursday and Friday
before sliding back toward the seasonal averages Saturday with the
crossing front.


Active weather will continue Sunday and Monday before upper ridging
begins to build back in over the region the remainder of the
week...limiting convection. This will drive temperatures back up into
the 90s...potentially warmer than the current run of above normal
temperatures as latest model runs sow 598/599dm 500mb heights over
the region and ensembles show 20 year return intervals in heights
and temperatures aloft.


Isolated showers will continue to diminish with the loss of heating
and shouldn't have any impacts on area terminals. High pressure in
place will bring a nearly clear sky and calm wind overnight, which
may allow some shallow valley fog in the typical spots. Have included
slightly reduced VSBY for FKL, DUJ, and LBE as a result.

Otherwise, VFR is expected to prevail. Scattered Cu field will
develop again tomorrow afternoon with heating, and a few scattered
showers/thunderstorms will be possible.. especially around the PIT
area terminals where hi-res models agree on convection initiating.

Restrictions are possible again Friday night as a low pressure system
and corresponding cold front cross the region.


Based on the 30-year climatological average, here is the "normal"
number of 90-degree days per year at each of the local climatic

Pittsburgh: 6.9 days
Morgantown: 8.0 days
Wheeling: 5.0 days
Zanesville: 10.0 days
Dubois: 1.0 day

90+F temperatures are still forecast through Friday. Here is a
summary of the most-recent 90+F stretches at each site:

Pittsburgh (7/3-7/10/2020): prior 8-day stretch ended 8/20/1995
Morgantown (7/2-7/10/2020): prior 9-day stretch ended 8/4/1995
Wheeling (7/4-7/10/2020): prior 7-day stretch ended 7/27/2016
Zanesville (7/4-7/10/2020): prior 7-day stretch ended 7/8/2012
Dubois (7/5-7/10/2020): would be longest 90F stretch at DUJ.

Dubois most recently had a 5-day stretch of 90F days ending
7/23/2011. Dubois also is the site with the greatest potential
variability in the forecast maximum during this forecast period, and
therefore the most likely not to reach 90F on any given day.


OH...Heat Advisory from 1 PM to 8 PM EDT Thursday for OHZ039>041-048>050-
PA...Heat Advisory from 1 PM to 8 PM EDT Thursday for PAZ020-021-029-031-
WV...Heat Advisory from 1 PM to 8 PM EDT Thursday for WVZ001>004-012-021-


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