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-- Discussion containing changed information from previous version are highlighted. --
300
FXUS61 KPBZ 190551
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
151 AM EDT Tue Sep 19 2017

.SYNOPSIS...
Generally warm and humid conditions will prevail for the next
week across the area.

&&

.NEAR TERM /THROUGH TODAY/...
Easterly boundary layer flow bringing maritime air farther west
toward the ridges has allowed for the blossoming of
stratocumulus along the eastern slopes of the CWA tonight. This
has also allowed for dewpoints to start to tick up in the rest
of the CWA as an even more dank boundary layer flows westward.
Local dewpoints have been surging into the low to mid 60s across
the area as a result. If clear skies were in the cards like the
last couple of nights, this would likely mean abundant fog,
however the situation is a bit different over the next 12 hours
or so.

High clouds are starting to slowly advance eastward into eastern
Ohio vis-a-vis convective blow off. The wave responsible for
this convection to our west will be rapidly weakening as it
drives into the teeth of the resident high pressure over the
area over the next day or so. Multi-model projections suggest
some showers should wander into central Ohio by Tuesday
afternoon, however east of there the ridge should hold sway
fairly convincingly. Thus, realistically almost the entirety of
our area should remains largely dry other than a renegade shower
that would try to develop given the moist boundary layer in
place.

With said moist boundary layer, while away from the high clouds
that are advancing into Ohio, we have clear skies through
sunrise outside of the foggy valley locations, once again
destructive sunshine will result in abundant cumulus
development. Thus, cumulus over the eastern CWA and high clouds
in Ohio will yield no better than partly sunny skies anywhere in
the CWA by afternoon. However, given a very warm start and
continued warm advection off the deck, highs should largely rise
back into the 80s for most locations. Fries

&&

.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...
The main weather impacts of the entire forecast reside in this time
period.  The ever slow moving cold front dissipates, however a mid
level shortwave trough crosses the region Wednesday.  With dewpoints
still in the 60s, associated mid level cooling, and daytime heating,
scattered showers are possible during the afternoon and evening over
parts of eastern Ohio, southwestern Pennsylvania, and the mountains
of West Virginia/ Maryland. There is enough of a consensus from
several operation models and hints with low probability of a
hundredth of an inch from ensembles to include pops in the forecast
over the aforementioned location.

Any activity will wane with the loss of heating Wednesday night.
588dm H5 anti-cyclone re-establishes itself over the mid atlantic.
Despite a northerly trajectory of low level air, daytime highs
Thursday won`t cool off and we will keep our 80F streak alive at
most locations.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
Highlights:
- Continued Above Normal Temps
- No Rain Predicted
- Ten Straight Days above 80F+ /16th-25th/ possible @ PIT

Mid level ridging remains in place over the eastern United States,
as it will be for most of the work week.  This brings a broken
record forecast of patchy predawn fog especially in deeper valleys
giving way to a mostly sunny sky. Each consecutive day we are dry
the probability of fog will decrease given lower surface moisture,
but it will be offset by longer September nights.

H8 temps hover around 17C for the entire long term.  Energy block
method yields widespread lower to mid 80 values save for the
mountains where 70s will be common.  Elected to go with guidance
that does not contain bias corrected grids since we are in a
transition from below normal to an above normal stretch.

Any impacts from Maria will be beyond the scope of this seven day
forecast even mid and high clouds associated with the storm.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
Deterioration to MVFR and IFR is expected for most ports
overnight as fog develops. This should mix out within a couple
of hours after sunrise. VFR conditions with diurnal CU and
increasing mid/high clouds are expected for the rest of the TAF
period as a weak upper trough approaches.

.Outlook...
Other than local morning fog, no widespread restrictions
expected through Sat with building ridging.
-- End Changed Discussion --

&&

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

&&

$$