Area Forecast Discussion
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FXUS61 KPBZ 300944

Area Forecast Discussion
National Weather Service Pittsburgh PA
544 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


Minimal change needed at this time to the ongoing forecast based
on latest observations and trends. The previous discussion

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 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


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.


Surface high pressure will build into the area from the western
Great Lakes Monday night into Tuesday. This will allow the area to
remain in cooler northerly flow even as subsidence builds. A dry
forecast will thus be maintained through mid-week.

Ridging at all levels of the atmosphere should thereafter increase
from mid-week onward as amplification of the pattern is evident on
basically all guidance over the upper Mississippi Valley and
northern Great Lakes during the second half of the week. This
ridge and resultant low level thermal ridge should start to flop
over toward our area by Friday, which at this point looks to be
the warmest day of the next week or so, when temperatures should
push again well above normal.


General VFR is forecast through the evening with exceptions for
isolated convection which will wane with the sun. Mention will be
reserved for amendments given the declining coverage and questionable
location of cell initiation.

Given the frontal position and abundant low level moisture, expect
the return of some fog on Saturday morning, although mid level
cloudiness is expected to alleviate a widespread IFR threat. Will
hedge from previous pessimistic forecast with an MVFR mention.

Broad upper troughing should maintain periodic shower and thunderstorm
restriction potential through Monday.




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