Area Forecast Discussion
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FXUS61 KPBZ 240133

Area Forecast Discussion
National Weather Service Pittsburgh PA
933 PM EDT Sun Jul 23 2017

A stagnant mid-level trough will keep very humid conditions over
the region through Monday with a continued threat for showers
and thunderstorms. Dry conditions are expected through early
Thursday before a cold front approaches from the northwest.


A combination of factors is continuing to lead to heavy rainfall
over the area this evening. We are implanted directly in the
right entrance region of an upper jet streak with a slowly
moving short wave trough moving through. This is accentuation
differential PVA over the area all while a series of mesolows
track out ahead of an incoming cold front in an area of
increased low level convergence. Because the pre-frontal
activity has been developing in an area of much weaker shear as
well as a synoptic scale inflection point, cell movement has
been exceedingly slow. This has lead to ample problems with
flooding through the evening.

While flooding will remain a concern for several more hours, the
light is at the end of the tunnel. The regional radar mosaic
does indicate the back edge of activity is finally sagging
southeastward into central Ohio. While it will take a few more
hours to clear our area, it does seem that the heaviest rainfall
should be ending shortly. We will continue to monitor flood
guidance as many areas are near to critical thresholds.

Fog will develop overnight as layer RH values start to fall off,
however its ubiquity is questionable until the exact degree of
clearing can be ascertained. Fries


Mid level trough sweeps through Monday afternoon so this will
be the last round of showers/storms before a welcome break

Upper level heights will rise on Tuesday, and a broad surface
high will build into the Great Lakes. This will finally bring a
stretch of dry weather and sunshine for Tues/Wed.


A deep upper trough and associated surface cold front will
settle south from Ontario on Thursday, bringing the threat for
showers/storms during the afternoon and evening.

Forecast for Friday into the weekend gets a bit muddy. If the
aforementioned wave progresses into the Southeast, then the
weekend is shaping up to be spectacular with dry conditions and
highs around 80. Some model solutions open the upper wave up
across the Appalachians keeping the threat for clouds and
precipitation (especially over the eastern ridges) into Friday
and perhaps Saturday.


Showers and thunderstorms will continue to stream through the
area overnight as an upper-level disturbance swings through.
This could lead to visibility reduction with heavy rain in the
short term.

After the showers/thunderstorms move off to the east, deterioration
back to MVFR and possibly IFR is expected. A mix of morning
stratus and fog is expected over much of the area, with fog
favored in the clearing further west.

Expecting improvement to VFR through Monday morning. The very
slow moving boundary will sag south through Monday, re-
invigorating showers and thunderstorms in the afternoon, mainly
south of Pittsburgh.

VFR is expected to prevail toward midweek as high pressure
builds in.




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