Gibsonia, Pennsylvania Weather Forecast Discussion

613
FXUS61 KPBZ 240836
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
436 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 /UNTIL 6 PM THIS EVENING/...
KEY MESSAGES:
- Dense fog in spots across western PA this morning
- Shower/thunder chances increase again this morning with
  another shortwave. Possible instances of flooding mainly south
  of PGH
---------------------------------------------------------------
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 all PA
counties in the forecast area save for Washington and Greene
given observations and camera data. Currently it is in 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. Additionally, WPC has
pared back the "Marginal" risk of flooding to mainly south of
PGH.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
KEY MESSAGES:
-  Marginal flood threat
-  Rain and thunderstorm chances continue Thursday
----------------------------------------------------------------
Rain chances will persist into Thursday under deep southwest
flow as the upper low meanders over the Great Lakes.
Strengthening jet dynamics across West Virginia and western
Pennsylvania may result in more moderate rain overnight and into
the morning. With that, the Weather Prediction Center (WPC) has
placed portions of region mainly south of PGH under a
"Marginal" risk for flooding, but dropped the "Slight" risk that
was previously in place.
&&
.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 has consistently indicated a
ridge building over the region later in the weekend and into
Monday. This setup will likely bring drier conditions and warmer
temperatures early next week.
&&
.AVIATION /09Z WEDNESDAY THROUGH SUNDAY/...
There is fairly high confidence in the development of IFR/LIFR
flight conditions through dawn, 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.
Modest improvement to low MVFR is possible with some weak
mixing. MVFR/IFR 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. This activity will likely persist into tomorrow
evening.
.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>022-073>078.
OH...None.
WV...None.
&&
$$
SYNOPSIS...88
NEAR TERM...88
SHORT TERM...Hefferan/88
LONG TERM...Hefferan/88
AVIATION...CL/Shallenberger

NWS PBZ Office Area Forecast Discussion