Area Forecast Discussion
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FXUS61 KPBZ 182211 AAA
AFDPBZ

Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
511 PM EST Mon Dec 18 2017

.SYNOPSIS...
Warmer, but damp weather can be expected early this
week followed by cooler temperatures on Wednesday. The next
chance for widespread measurable precipitation will be later
Friday and into the weekend.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
515pm update...made minor adjustments to overnight PoPs in line
with latest radar imagery and hires model guidance. Temperatures
have been modified with a blend of hires guidance.

Previous discussion...

Drizzle is possible through the evening as a weak wave passes
over the moisture locked in by an inversion. Generally kept
PoPs low but a bit of an upslope component is expected as the
wind shifts more westerly aloft. Will keep highest chance values
here. Otherwise, low level moisture and clouds will remain
locked in place. Temperatures will be able to warm even with
modest mixing and will likely stay elevated, with minimal
diurnal range, overnight.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
Zonal flow will be maintained with weak forcing. Overcast skies
will persist, however, periods of light precipitation should
end by Tuesday afternoon as the depth of the saturated layer
decreases.

Warm southwesterly surface flow will continue the upward trend
in temperatures until a weak boundary drops south across the
forecast area Tuesday night and flow shifts to the northwest...resulting
in cooler temperatures on Wednesday. Stable conditions should
result in little more than continued cloud coverage.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
More amplified pattern is expected through the weekend as a
system ejects into the Plains. Strong warm advection will lend
to temperatures between 10 and 15 degrees above average until a
cold front approaches, but the timing is several days different
between the models. This obviously has an impact on whether we
will see rain or snow by the end of the weekend. Adjustments in
the extended were largely based on superblend and ensemble
guidance.

&&

.AVIATION /22Z MONDAY THROUGH SATURDAY/...
High confidence forecast of IFR cigs and drizzle through at
least this evening, if not longer. Weather patten remains
constant with abundant low level moisture trapped underneath
inversion socking clouds in place through most of Tuesday.

Would not be surprised if cigs teeter around 1KFT IFR/MVFR
threshold tonight before slowly returning to MVFR /015/ by mid
to late morning Tuesday. Most guidance has stratus lifting
tonight which seems odd, however looking at upstream
observations, MVFR cigs are out in Indiana and western Kentucky
so its possible especially after 3Z in the west then 6Z in
mountains.

Winds will be from the southwest between 8-11kt. Gusts near
20kts are possible after 15Z Tuesday.

.Outlook...
No widespread IFR weather is forecast.

&&

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

&&

$$



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