PBZ issues Area Forecast Discussion (AFD) at Sep 24, 2:01 AM EDT164
FXUS61 KPBZ 240601
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
201 AM EDT Wed Sep 24 2025
.SYNOPSIS...
Periodic precipitation chances will continue through the week
with seasonable temperatures. Mainly dry conditions should
return this weekend.
&&
.NEAR TERM /THROUGH TODAY/...
KEY MESSAGES:
- Dense fog in spots north of PGH this morning
- Shower/thunder chances increase again this morning with
another shortwave. Possible instances of flooding.
---------------------------------------------------------------
A weak shortwave ridge crossing the region early this morning
has ended any shower activity. With the limited cloud coverage
early this morning, recent rainfall, and light winds, areas of
fog have developed. Issued a dense fog advisory for PA counties
north of Pittsburgh given available surface observations and
satellite data. Currently it is effect until 9AM, but it is
possible we will be able to pare it back as cloud coverage
increases from the west. Overall, morning fog is expected to
dissipate between by mid-morning.
A sfc low is then progged to cross north across the forecast
area over the course of the afternoon. Effective shear values
will increase, CAPE values will still be relatively low, but
given the setup, cannot rule out a few strong storms. However,
the severe potential looks less likely this afternoon.
Piggybacking on the above, latest ensemble guidance shows joint
probabilities of 0% to 25% of CAPE>500j/kg and shear>30kts
during the day. SPC has removed the "Marginal" risk previously
in place over portions of the forecast area and went with just
general thunder with their latest update.
&&
.SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/...
KEY MESSAGES:
- Flood threat continues overnight
- Rain and thunderstorm chances continue Thursday
----------------------------------------------------------------
Rain chances will persist into early Thursday under deep
southwest flow as the upper low meanders over the Great Lakes.
Strengthening jet dynamics across West Virginia and western
Pennsylvania may enhance rainfall rates, leading to periods of
heavy rain Thursday morning. Isolated areas could receive 1-2
inches of rain in 6 hours. Given this potential, the Weather
Prediction Center (WPC) has placed portions of region under a
"Marginal" to "Slight" risk for flooding.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
KEY MESSAGES:
- Light showers expected Friday
- A building ridge will likely support warm and drier conditions
over the weekend
------------------------------------------------------------------
Behind the departing trough and cold front, the risk for heavy
rainfall will diminish as drier mid and upper-level air moves
in. A few isolated showers may develop early Friday, mainly
across the higher terrain due to lingering low-level moisture
and upsloping as winds shift from the northwest.
Looking ahead, ensemble guidance consistently indicates a ridge
building over the region Sunday into Monday. This setup will
likely bring drier conditions along with temperatures trending
warmer than average.
&&
.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
A band of showers/embedded thunderstorms associated with a 700mb
shortwave will continue to weaken and exit the region through
02Z. A period of mostly VFR conditions should ensue/continue
into the overnight hours under brief, temporary ridging.
There is fairly high confidence in the development of IFR/LIFR
flight conditions overnight, but there is still some uncertainty
whether these restrictions will manifest more as low stratus or
fog. Given the moist surface, nearly calm wind, and elevated
dewpoints, any prolonged clearing should result in the
development of IFR/LIFR fog, while increasing high clouds may
lead to favoring an IFR/LIFR stratus deck. For now, favoring fog
more than stratus between 06Z and 14Z.
Modest improvement to low MVFR is possible with some weak
mixing. MVFR ceilings will likely linger through the day. The
next shortwave and a NE lifting surface warm front is expected
during the day Wednesday, aiding another round of convection
during the afternoon. Have used PROB30 groups for both the
initial showers and likely later convection. IFR impacts are
possible in brief heavy rain, with gusty wind also possible.
.OUTLOOK....
Similar diurnal trends with rounds of rain can be expected for
Thursday into Friday morning before an 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...Dense Fog Advisory until 9 AM EDT this morning for PAZ007>009-
013>016-020-022-077-078.
OH...None.
WV...None.
&&
$$
SYNOPSIS...88
NEAR TERM...88
SHORT TERM...Hefferan/88
LONG TERM...Hefferan/88
AVIATION...CL
Source:
PBZ issues Area Forecast Discussion (AFD) at Sep 24, 2:01 AM EDT---------------
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