Area Forecast Discussion
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FXUS61 KPBZ 300911
Area Forecast Discussion
National Weather Service Pittsburgh PA
511 AM EDT SAT JUL 30 2016
Periodic showers and storms will continue through the weekend until
high pressure brings the return of dry conditions for much of next
.NEAR TERM /THROUGH TONIGHT/...
An approaching shortwave will help lift a stalled surface
boundary north across the forecast area today and upper level
divergence will also increase as the area transitions to a more
favorable position under the jet. This combined with a moist and
unstable boundary layer will result in more convective coverage
today. Progged instability is marginal with slim profiles and even
the chronically overdone NAM forecasting cape values to remain
under 1000, so the severe threat is low. Forecast precipitation
amounts over the 24 hour period will range from a quarter inch
across far southwestern zones, increasing to the northwest up to
three quarters of an inch on average over Jefferson and Forest
counties where the greatest synoptic lift will be. Locally higher
amounts will be possible at locations that see deeper convection
with PWATs around 1.75" on average and warm cloud processes
dominating but overall rain rates should remain reasonable given
the marginal instability.
.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Shower and storm chances will continue on Sunday as the upper
trough continues to transition east and the surface low associated
with the aforementioned boundary crosses across the north. Drier
air will finally begin to move in aloft on the backside of the
trough which will bring an end to shower/storm chances by Sunday
night. Maintained a dry forecast for Monday under continued dry
northwesterly flow, but there is an outside chance of afternoon
storms as latest model runs indicate a small jet streak developing
Monday afternoon and just enough low-level moisture remaining.
May need to include mention of showers/storms in future updates if
models show continuity with this feature.
.LONG TERM /TUESDAY THROUGH FRIDAY/...
Surface high pressure will keep the forecast dry through the
middle of the work week. Although the GFS suggests that an
isolated shower/storm could approach the region Thursday, will
stick with a slower solution shown by ensembles/ECMWF and hold off
on mention of precipitation until Friday with a cold front. With
500mb heights slowly building through the extended forecast,
temperatures should also slowly rise. Although highs on Tuesday
will start off near seasonable values, temps will approach the 90
degree mark in many locations once again by Friday.
.AVIATION /09Z SATURDAY THROUGH WEDNESDAY/...
Although fog cannot be ruled out this morning, as of 09Z it
appears that mid clouds may have negated much of that threat. The
exception at the moment is Latrobe as a result of clear skies
earlier in the morning hours. Although all locations are expected
to receive rain during the day, widespread restrictions do not
appear likely at this time. The best chance for restrictions will
come from any moderate/heavy showers/storms that develop. The
threat for fog/stratus Saturday night into Sunday morning depends
on rainfall during the day and how quickly clouds can clear out,
with nearly calm winds a factor that would promote restrictions.
.OUTLOOK /SUNDAY THROUGH WEDNESDAY/...
Broad upper troughing should maintain periodic shower and
thunderstorm restriction potential through Monday.