PBZ issues Area Forecast Discussion (AFD) at Sep 23, 1:07 AM EDT428
FXUS61 KPBZ 230507
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
107 AM EDT Wed Sep 23 2026
.WHAT HAS CHANGED...
Dry weather returns for all late on Wednesday. Looking at
chilly overnight lows at the end of the week.
&&
.KEY MESSAGES...
1) One last day of scattered showers across eastern Ohio before dry
weather returns
2) Below-normal temperatures linger through mid-week and moderate by
the weekend
&&
.DISCUSSION...
KEY MESSAGE 1...
We'll remain sandwiched between surface low pressure off to our
south and surface high pressure off to our northeast on Wednesday.
An inverted trough will pivot to the west into eastern Ohio and
focus one last day of scattered showers there. Latest HREF
probability for measurable precip suggests that coverage peaks in
the early morning hours before shifting southwest and ultimately
dying out as high pressure finally wins out with much drier air
pushing in from the north. The lower dew points have already
arrived in western Pennsylvania and will continue advecting
west, so expect that the day will be dry there. By late
Wednesday, we should see our whole area turn dry.
The column really dries out on Thursday and support for rain ceases
as an upper low closes off across the Mid-Atlantic and places us on
the dry, northerly flow side. Ensembles surge much lower 850-700 mb
RH values south, so clouds should scatter out and return some
sunshine. Ensembles then point toward a dry weekend locally as a
coastal low develops off the Mid-Atlantic and shortwave ridging
between that and a trough across the Dakotas becomes our dominant
feature. There remains a sliver of a chance that the coastal low
jogs farther west, and latest runs have suggested a trend in that
direction, which would bring some low PoPs as far west as Pittsburgh.
The latest ensemble QPF distribution has about 86% of the
members keeping Pittsburgh dry with a tail of values as high as
~0.4" and thus the mean being drug way up above the 95th
percentile. So, while there are a select few low probability high
outliers, even in the worst case scenario for Pittsburgh, the
rainfall totals are less than half an inch. Farther east at
Latrobe to Indiana, a similar distribution exists with about
0.6" on the high end.
KEY MESSAGE 2...
Slow moderation of temperatures begins on Wednesday as the
drier air starts to scatter out clouds, but beneath the cold
upper low and with persistent easterly flow, NBM advertises only a
40-50% chance of >65F in the PA & WV lowlands with a 60-80%
chance in southeastern OH. The ridges likely hold in the low
60s. Those probabilities gradually tick up into the weekend when
upper 60s and low 70s are favored to return. With that said,
we'll then flip from below normal highs to below normal lows as
high pressure establishes, dew points crash, and skies clear
out. Optimal radiational cooling conditions should peak Thursday
night when we even see some probability increase for lows <40F.
Those peak at around 50% down the PA ridges and increase quite
a bit into eastern Preston and Tucker Counties up to 80-90%.
Would not even be entirely surprised if the cold spots of Canaan
Valley come in near freezing.
&&
.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
Gradually improving conditions to VFR are favored through the
overnight hours. In fact, drier air has been quick to arrive from
the northeast and erode the MVFR restrictions at most sites outside
of ZZV and LBE where lower level moisture remains trapped despite
the persistent downsloping in easterly flow. Still think that,
following the more aggressively optimistic guidance,
restrictions erode there shortly after 06z and VFR should return
for all but ZZV. There, dew points remain higher with thicker
cloud coverage, and an inverted surface trough will drive
scattered showers from the overnight hours through the mid-
afternoon. Think that cig will hold at MVFR while vis is
predominantly VFR with periodic dips to MVFR in the heavier
showers. Once those clear in the afternoon, VFR returns.
Easterly wind will remain stiff on Wednesday around 10 knots gusting
to 20-25 knots at times.
Outlook...
A prolonged period of VFR, possibly only broken locally by
steam fog migrating off of the rivers, returns for the remainder of
the week. Our next shot at active weather and higher probability
restrictions doesn't look to come until the end of the month.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
DISCUSSION...MLB
AVIATION...MLB
Source:
PBZ issues Area Forecast Discussion (AFD) at Sep 23, 1:07 AM EDT---------------
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