Area Forecast Discussion
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FXUS61 KPBZ 231924

Area Forecast Discussion
National Weather Service Pittsburgh PA
324 PM EDT SAT JUL 23 2016

Hot and humid conditions will continue. The best chance for
showers and thunderstorms will return on Monday with the passage
of a weak cold front.


Weak boundary, indicated mainly from a wind shift in surface obs
and lower dewpoints over Northwestern PA and NY, is bisecting the
CWA. This will be the focus for the development of widely
scattered thunderstorms through the rest of the evening as it sags
south. With plenty of instability, weak shear, and the support of
a passing short wave, some storms may be strong, with DCAPE values
suggesting a few downbursts may be possible. This is also
highlighted by a marginal risk that has been added by SPC. Will
maintain low chance pops from about Pittsburgh southward, where
the best low level moisture resides. Convection should diminish by
sundown, with the loss of heating.

While dewpoints have dropped off over our northern zones, 70
dewpoints are still prevalent south of I-70 and in Ohio where
temperatures have soared into the mid 90`s. The heat advisory
remains in effect there for heat indices near 100.

Model guidance suggests that these drier dewpoints will never
fully make it across the entire region before southerly flow
returns ahead of the next front Sunday. But, this should be
sufficient enough to provide a cooler night, for the northern
half of the region, than previous nights.


Upper ridge will build eastward briefly on Sunday, with a weak
shortwave crossing the lower Great lakes in advance of a front
that is progged to cross on Monday. Anticipate that most of Sunday
should remain dry, with warm and humid conditions continuing. 591dam
heights build overhead, so again anticipate temperatures exceeding
90 although some high clouds may limit heating for the
northwesternmost zones. At this time, with the uncertainty in
cloud cover, have not expanded in time the heat advisory for Ohio
but will continue to highlight the concern in the HWO.

An upper-level trough and its associated front will approach from
the west early Monday. Based the current model run timing, some
precipitation may already be moving into the area Monday morning,
which may limit the threat for any strong to severe storms despite
instability and moderate shear. For now, agree with SPCs analysis
of a Marginal Risk for the region. Ahead of the boundary, where we
remain cloud free early, temperatures should still warm well into
the 80`s and approach 90. Front will stall just south of the PA/MD
border by Monday night and we will remain in zonal flow. This
could lead to lingering chances of showers/storms, mainly along
the terrain on Tuesday. While dewpoints will be lower, it should
still be another day of mid-80 temperatures.


Zonal flow will be replaced by weak troughing over the eastern
CONUS for the end of the week. With several shortwaves progged to
pass in the upper level pattern, but differences in the
deterministic models, have opted to stay close to a blend of
guidance with near or slightly above normal temperatures forecast.


vfr conditions this afternoon. Some lower dewpoint air in moving
in in the northern airports like KDUJ and KFKL. it will gradually
move southward. In airports from KZZV to KPIT to KLBE and south,
there is a chance of an isolated thunderstorm after 19Z as the
drier air acts as a lifting mechanism. some mvfr restrictions in
the early morning hours sunday possible at in airports from KZZV
to KPIT to KLBE and south.

Restrictions will be possible late Sunday and Monday with the
approach and passage of a weak cold front.


OH...Heat Advisory until 8 PM EDT this evening FOR OHZ048-057>059-
WV...Heat Advisory until 8 PM EDT this evening FOR WVZ004-012.


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