Area Forecast Discussion
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FXUS61 KPBZ 281838
Area Forecast Discussion
National Weather Service Pittsburgh PA
238 PM EDT Wed Sep 28 2016
Upper level low pressure will bring rain to our region for the
rest of the week.
.NEAR TERM /THROUGH TONIGHT/...
The late afternoon update featured further tweaks to POPs and
clouds based on the latest obs and high res trends which favor a
slower precip onset.
Otherwise, upper low pressure will continue to dig over the
Midwest during the near term. Convective temperature will thus be
falling and shower chances increasing through the night. Dry
layers within the atmospheric column will continue to provide
Overnight temperature will fall below convective thresholds, but
shortwave impulse/occluded front is progged to rotate around the
parent-low and maintain likely shower chances for the night.
.SHORT TERM /THURSDAY THROUGH FRIDAY/...
The aforementioned low is forecast to briefly stall over the
Middle Ohio River Valley on Thursday, before lifting northward and
filling once again through the weekend. The concern for the period
is for Thursday when an Atlantic moisture tap is forecast to
stream across I 68 through Garrett County and over areas generally
along and north of the PA turnpike, and deepen the overall
moisture supply in the column.
Currently-progged rain-supporting dynamics for that period are
limited given the lack of convergence/mid level frontogenetical
forcing in this mature stage of the low. The better probability
for heavy rain off the immediate eastern upslope areas should thus
be convection based and instability is not impressive.
Have used general River Forecast Center QPF for todays prog of
the event in conjunction with WPC QPF probability maps. The bottom
line is no flash flood watch until precursor rainfall tonight at
least defines a better threat area in conjunction with moisture
convergence into the occluded frontal zone.
As the Atlantic moisture tap in interrupted by Friday, the sustained
rainfall threat will be alleviated with more scattered convection
providing the rain chances.
.LONG TERM /SATURDAY THROUGH TUESDAY/...
The low is forecast to lift northward and fill through the weekend
with dry flow returning and diminishing rain chances for the
region, and supporting seasonably warm temperature.
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
VFR will predominate into the eveing, but deterioration can be
expected tonight and into Thursday as rain becomes likely with
moisture streaming into the eastern flank of the upper low.
.OUTLOOK /THURSDAY NIGHT THROUGH SUNDAY/...
Periodic restrictions can be expected into the weekend as the
upper level low lingers, then slow lifts north of the region.