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FXUS61 KPBZ 170948

Area Forecast Discussion
National Weather Service Pittsburgh PA
548 AM EDT Wed Jul 17 2019

The remnants of Barry will produce periods of showers and thunderstorms
through Wednesday night, with locally heavy rain likely. A hot and 
humid airmass will remain in place through the weekend.


530am update...
Small tweaks to near term PoP and temps to better capture current
radar and sfc ob trends, but the overall forecast message remains the

Previous Discussion...

Widespread showers and thunderstorms are expected through tonight as
the remnant wave of Hurricane Barry shifts from Indiana through the 
upper Ohio River Valley and into the northeast U.S. Storms will 
become more focused and organized during the late afternoon and 
evening hours along a cold front that will drop south out of the 
Great Lakes. Slight drier and cooler air plus NW flow behind the 
front will end precip chances, with the front moving through the 
entire area by Thursday morning.

The warm, humid environment Today will be characterized by marginal 
CAPE, weak shear, and notably deep moisture with PWATs 2.5 SD above 
normal. Expect fairly efficient rain making processes that will allow
for significant accumulations in short periods of time, making flash
flooding the predominant weather threat for Today. However, given 
fairly dry grounds resulting in higher FFG and hi-res models lacking 
enough high QPF signatures, will forego a flash flood watch at this 
time. A watch may be needed if more training of storms occurs, so 
radar trends will need to be monitored.


Brief NW flow behind the cold front and exiting Barry remnants
Thursday morning will quickly becoming a building ridge by the
afternoon. Building pressure heights will allow for hotter high
temperature Thursday despite the cold frontal passage, with most
areas above normal. Residual moisture along the eastern ridges into
the WV mountains plus daytime heating may allow for a few afternoon

Increasing heights and moist southerly sfc winds are expected Friday
into Saturday as the 500mb high becomes centered over southern WV,
resulting in hot and humid conditions with little chance for rain
outside of iso storms Saturday afternoon. Confidence is high that 
most locations outside of the higher terrain will reach Heat Advisory
criteria (apparent temperature of 100F or higher) both Fri/Sat, with
increasing confidence of Heat Warning criteria (105F or higher) for 
southeast OH into portions of extreme western PA. Social Media and 
HWO messaging will continue but, given potential impacts with heavy 
rains Today, will delay any hazard issuance at this time. 

While low, there is a chance of a storm complex moving out of the 
Great Lakes and into our northern CWA late Thursday night into
Friday. This rain and its resultant cloud cover could also alter the
heat advisory potential.


The ridge will begin to break down Saturday night through Monday as 
a series of shortwave troughs roll through the region with periods of
showers and thunderstorms. The trough axis should dig farther south
by Tuesday in conjunction with a sfc cold front, resulting in a 
return to drier weather and near normal temperature.


Clusters of showers with very isolated thunderstorms continue to lift
across the region mainly north of PIT this morning. Expect this
activity to depart by around 12Z, with a very short lull in rain
coverage. Most locations will start out VFR, save for early dips to

Coverage of showers and storms will increase later this morning as 
deeper moisture and the upper wave associated with the remnants of 
Barry arrive. Ceilings will likely straddle a low VFR/high MVFR 
line across the region, with terminals east of PIT most likely to
remain with prevailing VFR ceilings. Thunderstorms are expected to 
form to the northwest along a weak front stretching along an 
ERI/AKR/CMH line, and head southeast into the region during the 
afternoon. Timing the period of most impact remains tricky, and
elected to continue with prevailing SHRA/VCTS in the TAFs. Any storm
could of course provide brief MVFR/IFR restrictions. Precipitation 
will taper off this evening behind the weak front. Expect ceilings to
fall to MVFR and then IFR tonight, with some patchy fog possible as 
well, as low level moisture remains abundant.

MVFR/IFR restrictions may continue into Thursday morning. 



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