PBZ issues Area Forecast Discussion (AFD) at Sep 21, 7:45 PM EDT
311
FXUS61 KPBZ 212345
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
745 PM EDT Mon Sep 21 2026
.WHAT HAS CHANGED...
Updated discussion for the evening period and 00z TAF issuance.
&&
.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...
Light rainfall continues across much of the area with continued
overrunning. Flood risk in this activity is null. A southward
moving kink in the front has cleared our WV counties casting
large questions as to whether or not we can even support the
convection required to get heavy rain back into our WV counties
this evening. This chance looks to be falling as we speak, with
Tucker the most likely culprit if any. A fractured, weak
convective line in central WV poses little threat to our
northern WV counties but the area will continue to be monitored.
Later this evening and into the overnight period, a wave of low
pressure riding along the main frontal boundary just to our
south will reinvigorate showers especially to the south and east
of Pittsburgh in the higher terrain, and perhaps even a
thunderstorm or two in northern West Virginia with fumes of
MUCAPE. Precipitable water remaining above 1.5 inches and decent
warm-cloud depths of 10-11kft will continue to support efficient
rain rates. While a brief lull is possible late tonight into
Tuesday morning, additional rounds of showers are likely right
on through Tuesday night and into Wednesday at least, as an
upper trough slowly digs toward the region from the Upper
Midwest and potentially closes into an upper low Wednesday night
or Thursday morning in our general vicinity.
24-hour HREF mean precipitation totals from 8 PM tonight through
8 PM Tuesday generally range from 1 to 1.25 inches down the
spine of the ridges and through Morgantown. 90th percentile
totals are mostly between 1.5 and 2.5 inches, with a few 3+
bullseyes illustrating the localized high rainfall potential.
The probability of 1"+ hourly rates on the HREF through the
period is quite low, but think this may be a bit underdone,
especially into Tuesday morning, given the convergence potential
in the terrain and the still-high PWAT. Much of this area is
already quite wet, with 1-hour flash flood guidance values
around or just below an inch. While the flash flooding threat
overall may be decreasing especially after tonight,
overflow/areal flooding threats remain. Thus, elected to extend
a good portion of the Flood Watch through 12Z Wednesday.
Counties west of PIT/HLG were allowed to drop, as these areas
are expected to avoid the higher rain rates/overall precip
totals.
Support for rain continues through Wednesday and into Thursday
as the upper low develops, with higher totals backing a bit into
eastern Ohio - 0.50" to 1.0 mean 24 hour totals through 8 PM
Wednesday according to the NBM. We won't lose the support for
continued rain until likely Thursday when the upper low exits
and surface high pressure centered over New England establishes
and kicks the surface boundary out. There is still hope for a
drier pattern for Friday and next weekend.
KEY MESSAGE 2...
Cool temperatures are still figured for much of the week. Much
of southwest PA/eastern Ohio north of the surface boundary has
sunk into the 50s today, while 60s are maintained south of I-70.
Given the abundant cloud cover and stubborn east/northeast flow,
higher ridge locations may have trouble reaching 60 degrees
Tuesday through Thursday. Lower and mid 60s are still figured
west of the terrain, although lower values may again be possible
in rain-cooled air. Minimum temperatures will remain fairly
close to normal given abundant moisture, but daytime highs are
still figured to run 10 degrees below normal through Thursday.
&&
.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
Scattered showers are expected through the period at the TAF
sites. The saturated region will mainly be IFR and below through
just about the entire period. Winds are expected to be from the
north through a large part of the period with also period of
light and variable winds. Otherwise, expect some wind gusts
across the area up to 20 knots through the overnight and int
tomorrow.
Expect restrictions to persist through the night with low
stratus, fog, and passing showers impacting the terminals.
Thunderstorms are possible but have only been put in for MGW.
Outlook...
Restriction chances lingering through at least Wednesday with
plenty of moisture and on-and-off rain chances.
&&
.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...CL/AK
AVIATION...Shallenberger
Source: PBZ issues Area Forecast Discussion (AFD) at Sep 21, 7:45 PM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202609212345-KPBZ-FXUS61-AFDPBZ)
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