PBZ issues Area Forecast Discussion (AFD) at Sep 23, 7:10 AM EDT576
FXUS61 KPBZ 231110
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
710 AM EDT Tue Sep 23 2025
.SYNOPSIS...
An upper level disturbance will cross the region and will bring
the chance of showers and thunderstorms today and into tonight.
A cold front will cross on Wednesday renewing the chance of
showers and thunderstorms.
&&
.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:
- Rain chances continue today.
- Fog potential late tonight.
---------------------------------------------------------------
A 500MB shortwave trough will cross the region today as some
leftover showers traverse the forecast area through the morning
hours. Hi-res models continue to indicate morning showers
moving through but as daytime heating proceeds, some SB CAPE
will swell to around 1000 J/Kg but shear this afternoon will
only be around 20 knots. Rainfall expected today will continue
to be a day with prolonged steady rainfall. The afternoon will
stand to see scattered thunderstorms developing. In fact, the
NBM probs are giving around 75% for 0.50 inches and roughly 30%
to 50% for an inch or more of rainfall.
Heading into tonight, the instability for the scattered activity
during the will quickly wane as showers and thunderstorms weaken
and dissipate in the 23Z to 02Z time frame. Cloud cover tonight
stands to be extensive and the potential of fog development will
depend on any breaks in the cloud cover.
&&
.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
KEY MESSAGES:
- Excessive Rainfall Outlook for Wednesday and Thursday.
- A few strong thunderstorms possible on Wednesday.
----------------------------------------------------------------
The Wednesday period will feature another shortwave trough
swinging through the area. As the trough swings through the
area, showers and thunderstorms will begin to develop by midday.
Hi-res models suggest the northern parts of the forecast area
will struggle to see 500 J/Kg MU CAPE due to the extensive cloud
cover. However, some breaks are possible in the south where some
MU CAPE values of 1000 J/Kg will be possible. Mainly into the
northern WV counties and SW PA counties, a Marginal Risk of
damaging wind has been issued. As well, the HREF suggests that
Wednesday will feature PWATS will have an 80% to 90% prob of
being greater than 1.5 inches. Thus, the WPC has put this area
into a Slight/Marginal risk of Excessive Rainfall.
This will continue into Wednesday night with a general lessening
in coverage of shower activity. Temperatures will still be quite
warm with lows in the lower 60s for lows. By Thursday, the cold
front to the west will begin to move into the region with
another day of a Marginal Excessive Rainfall. Convection will
be along the front and with the focal point for ascent, the NBM
probs are giving roughly 50% of 1 inch of precip or more for
Thursday. By Thursday night, the front will have moved through
the area with cooler temperatures expected. Another fog night is
possible here.
&&
.LONG TERM /FRIDAY THROUGH MONDAY/...
KEY MESSAGES:
- Lingering showers on Friday.
- A ridge will build into the area over the weekend.
------------------------------------------------------------------
By the end of the workweek, a long-range ensembles suggests a
ridge will build over the Ohio River Valley from Friday through
Sunday, bringing decreasing precipitation chances. The last of
the 500MB trough passing the Upper Ohio Valley will be late in
the day on Friday. This will suggest that a few showers may be
lingering over the area. Saturday may have a few lingering
showers but the chance is expected to wind down in the morning.
The Sunday Monday timeframe will feature the ridge building
into the area. A dry forecast is expected for Day 6 and 7.
Afternoon high temperatures are projected to run about 5 degrees
above average, topping out in the mid-70s. Overnight lows
should remain near average, especially if clear skies favor
radiational cooling in the wake of passing cold front.
&&
.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
A weak 700mb shortwave will maintain a region of lift over a
moisture environment to produce periods of scattered to numerous
rain showers through the evening. Thunderstorm potential favors
the afternoon period and generally locations S/E of KPIT where
instability best exists through the freezing level. Any
shower/thunderstorm that contains heavier rain could briefly
lower visibility further than forecasted as well as cause
temporary gusts to 35kts. There is high confidence in shortwave
ridging creating a lull in convective activity after 02z tonight
until the next shortwave arrives later Wednesday.
The more difficult aspect to discern is area ceiling trends
given abundant moisture across the region but high variability
in timing of daytime improvements and cloud coverage overnight.
In general, the expectation is for gradual improvements from
MVFR/IFR to VFR/localized MVFR through 00z amid diurnal heating
and continued areal lift. Thereafter, hi-res modeling seems to
diverge based on the degree of cloud clearing overnight. More
rapid clearing of various decks likely lends to greater fog
(less than 1/2 mile) and LIFR stratus development for most
terminals; lingering clouds combined with moisture convergence
may cause rapid east to west spread of an IFR to locally LIFR
stratus deck that limits fog production.
.OUTLOOK....
The next shortwave will traverse the upper Ohio River Valley
region starting Wednesday morning, spreading showers and
isolated thunderstorms NE. It will likely maintain at least MVFR
cigs (50-60% probability) through the day for most sites as it
offsets typical improvements from increased daytime lift/mixing.
Similar diurnal trends with rounds of rain can be expected for
Thursday into Friday morning before the upper trough axis
finally shifts east of the region. There is then increased
confidence in a drier weekend period with longer intervals of
VFR conditions.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...Shallenberger
NEAR TERM...Shallenberger
SHORT TERM...Shallenberger
LONG TERM...Shallenberger
AVIATION...Frazier
Source:
PBZ issues Area Forecast Discussion (AFD) at Sep 23, 7:10 AM EDT---------------
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