Area Forecast Discussion
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FXUS61 KPBZ 231824

Area Forecast Discussion
National Weather Service Pittsburgh PA
224 PM EDT Wed Aug 23 2017

Calm weather is expected today before a low chance for showers
returns on Thursday. Below-average temperature and less-humid
air will continue through the weekend.


Steep low-level lapse rates will support modest instability
sufficient to generate a cu field by early afternoon, but the
lowering inversion height will limit vertical depth and any
chances for precipitation. If a fetch off the lake can inject a
moisture plume into this environment, isolated showers will be
possible, but the probability is too low to mention.

A low-amplitude shortwave trough is depicted in most models to
move through this evening, grazing the nrn section of the
forecast area and generating light precipitation. Minimal PoPs
were included with this feature, which primarily will offer
increasing cloud cover.

Overall, today`s temperature will end up below seasonal averages
with maxima in the mid 70s and lows in the upper 50s.


A broad upper trough in the ern CONUS will dominate the wx
pattern through much of the remaining forecast as an upper ridge
amplifies in the central CONUS.

On Thu, a shortwave trough will impact the Ohio Valley, leading
to increased cloud cover and slightly-increased chances for rain
showers. Coverage and amount of rain will depend on atmospheric
moisture return, which will be meager amid sfc high pressure.
So, PoPs were increased, but QPF remains light.

Persistent nwly flow will maintain a steady-state environment
through Friday night, with little in the way of rain chances and
generally sunny and less humid conditions.


A high-confidence wx pattern is predicted through early next
week, as surface high pressure builds swd from the Great Lakes
amid an amplifying ridge in the central CONUS. The Ohio Valley
will lie between this ridge and the persistent upper trough on
the east coast. The resultant nly flow will maintain temperature
below seasonal average into the middle of next week.

By next Tuesday, moisture streaming from the Gulf in association
with tropical system Harvey may provide a canopy of high clouds
and an increasing chance of light rain.


VFR conditions are expected through the TAF period with diurnal
CU under building surface high pressure. Some MVFR restriction
are possible Thursday morning with isolated morning fog through

No widespread restrictions expected under surface high
pressure. MVFR possible in morning fog Friday through Saturday.





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