Area Forecast Discussion
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811
FXUS61 KPBZ 252125 AAA
AFDPBZ

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
525 PM EDT Mon Sep 25 2017

.SYNOPSIS...
High pressure will bring dry and warm weather through mid-week
before the passage of a cold front heralds a return to
seasonably-cool conditions.

&&

.NEAR TERM /THROUGH TUESDAY/...
525pm...only minor changes to the cloud cover. Rest of the
forecast is in excellent shape.

Upper ridging on the nrn side of Hurricane Maria will maintain
broad subsidence over the region, leading to dry mid levels and
only passing cirrus. Temp maxima in the upper 80s and dewpoints
in the 60s should slow the falloff of temps this evening until
late tonight, when localized fog may form again in the river
valleys as the boundary layer nears saturation.

Tuesday will see little change in the overall pattern, and
therefore little change in the forecast apart from a slight
cooling of H8 temperature. Hence, Tue maxima may end up slightly
below those observed today. Despite deep mixing, a mid-level
inversion will limit vertical development of clouds, suppressing
any precipitation during the day.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY NIGHT/...
A shortwave trough will deliver a glancing blow to the western
Great Lakes region, driving a cold front sewd on Wed as Maria
comes as near as it will get to the Delmarva coastline. After
another warm day on Wed, this front will make a swd push Wed
evening and help escort the hurricane out to sea, but will also
serve to scour out the low-level warmth and moisture from the
area.

Models are somewhat aggressive on moisture ahead of the
approaching boundary, which appears to be contributing to
broader coverage of precipitation as the models develop
instability. Given a more-realistic dewpoint in the low-mid 60s,
instability is more meager, so PoPs with the frontal passage were
reduced from the default model blend values.

High pressure returns on Thu with a marked cooldown expected.
After the summer-like temperature experienced recently, maxima
in the upper 60s will feel rather cool, although hardly
unseasonable.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
As an upper ridge builds into the Great Plains, a shortwave
trough will move sewd across the Great Lakes. Lacking boundary-
layer moisture, the extent of any precipitation is unclear. But
models signal at least a possibility of measurable light
precipitation during the wave`s passage on Fri.

In the wake of the wave, high pressure returns for Saturday,
with seasonable temperature through the weekend. Models diverge
thereafter on the upper pattern, with both models indicating a
wrn trough, but the GFS suggesting an amplifying upper ridge for
the ern CONUS and a slower approach of the trough to the Great
Lakes region. Given these discrepancies, did not deviate
significantly from the default model blend values in the
extended periods.

&&

.AVIATION /22Z MONDAY THROUGH SATURDAY/...
High pressure will maintain light southeast wind and VFR
through the TAF period. In the early morning hours of Tuesday
morning some non-VFR visibility restrictions possible from
patchy morning fog.

.Outlook...
Restrictions are possible with cold fronts Wed night and Fri.

&&

.CLIMATE...
While we will not be quite as warm as over the weekend,
temperature this afternoon still will be 15 or more degrees
above seasonal averages this afternoon. Here are the local
record high temperatures for Monday:

PIT: 92 (1881, 1900)
ZZV: 94 (1908)
MGW: 93 (1930)
DUJ: 87 (2007)
HLG: 91 (1934)
PHD: 91 (2007)

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
MD...None.
OH...None.
PA...None.
WV...None.

&&

$$



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