060
FXUS61 KPBZ 211138
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
738 AM EDT Mon Sep 21 2026

.WHAT HAS CHANGED...
Additional rain through Monday morning is likely south of
Pittsburgh with another round of heavier rain in that same area
Monday night.

&&

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

2) Much cooler temperatures arrive by mid-week

&&

.DISCUSSION...
KEY MESSAGE 1...
An MCS that moved into central West Virginia Sunday
evening will provide a shield of stratiform light to moderate rain
with embedded thunder across eastern Ohio overnight Sunday night.
While true flash flood concerns are lower, some localized heavier
rates are tracking into southeastern Ohio and will bear monitoring
for a flash flood threat. Otherwise, longer-duration higher
amounts atop an already saturated ground that received 2-3" in
the past 24 hours from eastern OH to southwestern PA could
result in rises on creeks and streams and an areal flood
concern. Come Monday morning, we`ll have to monitor a few
features for a continued flooding threat. A slowly meandering
boundary is progged by 00z guidance to park right around the
Mason Dixon Line through the day as another wave rides along it,
and the strongest convergence/overrunning would support the
bulk of the rain in northern WV and far southwestern PA in the
morning. The 00z HREF 6 hour mean through 10am paints 0.5- 0.75"
along the I-70 corridor while the LPPM is around 2-3x that
total which suggests that some convective enhancement is
possible, so headed into the morning hours on Monday, focus will
shift to that area. The 00z CAMs have exhibited a slight shift
to the north in the boundary location, so if this footprint of
QPF was to shift one way or the other, would think that a slight
northerly jog is in play, though still remaining south of
Pittsburgh. Given the very saturated ground already in place,
and ensemble mean PWAT values at 1.7-1.9", a Flood Watch remains
in effect through noon Monday.

CAMs then suggest another general lull Monday afternoon into the
evening, and this is why the Flood Watch only extends through noon
for now. Another impulse arrives late Monday evening as does weak
low pressure riding along the surface boundary, and both features
look to reinvigorate showers and storms again, this time along the
ridges (best orographic ascent on the eastern side with a
southeasterly wind) and north of Pittsburgh. Ensemble probability
for >1" of rain then from Monday morning through Tuesday morning
reaches 60-80% south and east of Pittsburgh with a finger of lower,
but not zero, probability extending back from Indiana to Butler
County. The probability of >2" is up to around 40% and >3" around
20% as well southeast of Pittsburgh, so higher end totals in that
area are certainly on the table. That said, the flashy nature to the
rainfall is still lower probability as the chance for >1"/hour rates
in any given hour in that same timeframe doesn`t reach much higher
than 20%. In any case, flood threats will be maintained through at
least Wednesday.

Another upper trough arrives Tuesday into Wednesday, and ensemble
means close this one off into a broad low which means we won`t lose
the support for continued rain until likely Thursday when it exits
and surface high pressure centered over New England establishes and
kicks the surface boundary out. With this round, the higher totals
are painted across eastern Ohio where NBM mean 24 hour amounts
through 8 PM Wednesday sit around 0.75-1" but still suggest the
potential for higher amounts with the 75th to 90th percentiles of
1.5-2". Some showers may even linger into Thursday as the main
approaching trough possibly closes off into an upper low. There is
still hope for a drier pattern for Friday and next weekend.

KEY MESSAGE 2...
Cool temperatures remain the second part of the story this week.
Given the abundant cloud cover and stubborn east/northeast flow,
higher ridge locations may have trouble reaching 60 degrees Tuesday
through Thursday, while lower and mid 60s will be common west of the
higher elevations. While minimum temperatures will remain fairly
close to normal, daytime highs may run some 10 degrees below
climatology during the midweek period.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
Rain showers may persist throughout the day, but periods of
lower, more scattered coverage are likely into the afternoon and
evening along with the potential for some meager mixing. MVFR/IFR
cigs/vis are still expected for much of the day due to the
copious moisture in the low-levels. FKL and DUJ should see a
light shower but otherwise remain VFR with a BKN to OVC mid-
level deck. A stout easterly wind establishes this afternoon
around 10 knots gusting to 15-20 knots at times.

Another push of rain and embedded thunderstorms arrives after
sunset Monday night with highest probability for restrictions
coming for PIT, DUJ, LBE, and MGW. Ceilings will drop region-
wide after this round of rain moves out of the area due to the
lingering low-level moisture.

Outlook...
Low cigs are fog are likely into Tuesday morning with
restriction chances lingering through at least Wednesday with
plenty of moisture and on-and-off rain chances.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Flood Watch until noon EDT today for PAZ020-021-029-031-
     073>076.
OH...Flood Watch until noon EDT today for OHZ039>041-048>050-
     057>059-068-069.
WV...Flood Watch until noon EDT today for WVZ001>004-012-021-
     509>514.

&&

$$

DISCUSSION...MLB
AVIATION...MLB/Lupo