336
FXUS61 KPBZ 220536
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
136 AM EDT Tue Sep 22 2026

.WHAT HAS CHANGED...
Updated for 06z TAF issuance. Unsettled weather continues
through mid-week, but confidence is increasing in a dry
upcoming weekend.

&&

.KEY MESSAGES...
1) Rain chances continue much of this week. Longer duration rainfall
totals could be high and lead to localized flooding and/or river
rises into Wednesday morning.

2) Below-normal temperatures linger through much of the week.

&&

.DISCUSSION...
KEY MESSAGE 1...
A wave of low pressure riding along the east-west draped boundary
now analyzed off to our south will reinvigorate showers and storms
during the early overnight hours Monday night. From roughly
I-70 on north, where temperatures will hold in the low 50s,
light stratiform rain will be the theme with a persistent
easterly wind. South of I- 70, temperatures are a bit warmer and
fumes of MUCAPE will support higher coverage and intensity of
showers and embedded thunderstorms driven by an inverted surface
trough from the aforementioned low. Precipitable water values
have dipped a little bit back toward 1.5", and as has been the
case for the past couple days, HREF and REFS probability for
1"/hour rainfall rates is low. It`ll be the longer duration 3
hour amounts and associated river rises to monitor. Latest hi
res guidance pushes the rain off to our east in the latter half
of the overnight hours.

That surface trough won`t budge much into Tuesday, and we`ll see
coverage of showers increase again through the day. An upper trough
will approach from the west and begin to slow down and close off
into a low. The broad nature of the forcing with diffluent mid-level
flow and the inverted trough is giving Tuesday more of a scattered
shower type look rather than a more coherent shield of rain. PWAT
values come down a touch more and the column dries a bit in the mid
and upper levels, but showers will still be productive with the bulk
of the moisture in the warm cloud layer. Still not concerned about
hourly rates as the 10 km neighborhood probability for 1"/hour in
any given hour is 20% or less. 24 hour mean totals from HREF through
8am Wednesday range from a quarter to three quarters of an inch, and
even the 90th percentile peaks around 1.25-1.5 inches south of
Pittsburgh. While the flash flooding threat overall may be
decreasing especially after tonight, overflow/areal flooding threats
remain. Thus, the Flood Watch continues through 12Z Wednesday.
Counties west of Pittsburgh were dropped as these areas are expected
to avoid the higher totals.

Support for rain continues through Wednesday and into Thursday as
the upper low develops with highest coverage shifting west into
eastern Ohio in tandem with reorientation of the surface trough and
PVA around the closing upper low. Guidance actually favors coverage
decreasing into the afternoon and evening hours which makes sense as
we become more centered beneath the upper low and lose the forcing
locally, all while surface high pressure over New England begins its
attempt to nudge southwest. We won`t lose the support for continued
rain until likely Thursday when the upper low exits and the surface
high better establishes and kicks the surface boundary out. Longer
range 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.

KEY MESSAGE 2...
Beneath the cold upper low, with persistent easterly flow, and
beneath thick cloud cover and showers, NBM advertises a 60-70%
chance that our I-80 areas and down the PA & WV ridges can`t get
above 60F for highs on Tuesday, and similar probabilities
remain in the ridges on Wednesday. Elsewhere, the goal posts
spread from low 60s on the cool end to mid 60s on the warm end,
and given the conditions in place, it`s likely a better bet to
hedge cooler. Minimum temperatures will remain fairly close to
normal given abundant moisture, but daytime highs will run 10
degrees below normal through Thursday. So, even optimistically,
mid 60s is likely our ceiling through Thursday before more
seasonable temperatures return for the weekend.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
A moderate to high confidence IFR and lower forecast is in place
through most of the TAF period. Plenty of near-surface moisture as
well as deep column saturation will maintain low cigs and periods of
mist and rain showers along an inverted surface trough through
Tuesday. The one difference on Tuesday compared to the past couple
days is that the coverage should take on more of a scattered shower
nature as opposed to a broader shield of light to moderate rain. For
this reason, have kept the RA mention through the pre-dawn hours on
Tuesday, but then transitioned to SHRA during the daytime. Vis
should predominantly hold at 6SM or higher with periodic
restrictions lower in periods of more moderate showers. Cigs are
favored to hold at IFR through Tuesday, though some meager diurnal
mixing could raise them to near MVFR threshold in the afternoon
hours. Not all that optimistic in that solution given the thick
cloud coverage that would have to mix out, but LBE may actually fare
slightly better as stiff easterly wind around 10-15 knots downslopes
off of the ridges and locally improves cigs a bit.

Improvement to at least MVFR is possible late Tuesday night as the
surface trough gradually shifts east.

Outlook...
Restriction chances linger through at least Wednesday with plenty of
moisture and on-and-off rain. Conditions are favored to improve come
Thursday as the pattern turns drier into the weekend.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch through Wednesday morning for PAZ021-029-031-
     073>076.
OH...Flood Watch through Wednesday morning for OHZ059-068-069.
WV...Flood Watch through Wednesday morning for WVZ002>004-012-021-
     509>514.
&&

$$

DISCUSSION...MLB
AVIATION...MLB