PBZ issues Area Forecast Discussion (AFD) at Sep 27, 7:32 PM EDT
318
FXUS61 KPBZ 272332 AAA
AFDPBZ
Area Forecast Discussion...UPDATED
National Weather Service Pittsburgh PA
732 PM EDT Sat Sep 27 2025
.SYNOPSIS...
Rain showers south and east of Pittsburgh on Saturday. Dry and
unseasonably warm on Sunday and Monday. Low rain chances for
northern West Virginia early Tuesday but otherwise dry with a
cooling trend through the rest of next week.
&&
.NEAR TERM /THROUGH SUNDAY/...
KEY MESSAGES:
- Showers continue southeast of Pittsburgh through this
afternoon before clearing out tonight
- Patchy fog possible late tonight into early Sunday morning
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A deep trough over the southeast CONUS lifts northeastward
towards the Mid-Atlantic coast through the near term as high
pressure builds into the region from the west. With this
pattern shift, the ongoing shower activity southeast of
Pittsburgh should diminish and move off to the east along with
the cloud cover that has covered most of the area. Lingering
low-level moisture, in combination with efficient radiative
cooling under clearing skies and drying mid levels, will allow
for patchy fog development overnight. Low temperatures continue
to trend around 5 to 8 degrees above seasonal averages, only
dropping into the mid to upper 50s in most places by early
Sunday morning.
&&
.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY/...
KEY MESSAGES:
- Dry and warm on Sunday and Monday
- Increased cloud coverage Monday
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Ensembles support the upper low cutting off from the flow on Sunday
with height rises locally downstream of building ridging to our
west. Meanwhile, surface high pressure establishes across the Great
Lakes keeping us dry to close out the weekend and warmer than
Saturday with less cloud cover. It'll be unseasonably warm with an
80+% chance of >80F for highs. Dew points should mix out some, but
it could still feel more like the mid 80s by the afternoon.
Still dry on Monday as the surface high gradually weakens but
remains in control. The only notable difference will be an increase
in cloud coverage from the southeast with moisture extending north
from now Tropical Depression Nine. Highs are thus likely to be a few
degrees cooler than Sunday, especially south and east of Pittsburgh
where cloud cover resides for more of the day.
&&
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
KEY MESSAGES:
- Uncertainty for the beginning of next week dependent on tropical
low development and track
- Trend is toward a dry solution locally
-------------------------------------------------------------------
Eyes turn to the Atlantic at the beginning of next week with TD9 set
to approach the Carolinas by Tuesday and Hurricane Humberto
remaining well offshore. A complicated pattern evolves with synoptic-
scale interactions and how all of this may unfold with numerous
solutions still in play. The bottom line right now is that
notable impact to our area is not expected, and the trend
locally has been toward a drier one in the past 24 hours.
All ensembles support high pressure sinking south through Ontario by
mid-week, though differences in strength and timing of mid-level
waves lend some uncertainty to how quickly it builds and how strong
it is. The 24 hour trend has been toward a stronger, quicker
building high which favors a lean toward a drier, warmer solution
locally as TD9 turns east offshore of the Carolinas. The NBM
25th/75th MaxT spread Tuesday and Wednesday has shrunk now to around
5-7 degrees vs. the ten degrees 24 hours ago and is sitting in the
mid to upper 70s; primary uncertainty is stemming from question
regarding northward extent of cloud coverage from the system with
low end showing mostly sunny areawide and high end broken to
overcast. It still remains possible that TD9 gets absorbed by the
southeast CONUS trough/cut off low, very slowly meanders around the
coast, and extends moisture far enough north to bring some rain to
the southern part of our area on Tuesday. In this case, could see
mentionable PoPs extend as far north as Pittsburgh, but the latest
NBM follows trends of global ensembles and backs off rain mention
for nearly all of our area with only a slight chance creeping into
Preston/Tucker Counties.
With the increased cloud coverage, temperatures are likely to fall
off closer to normal (low 70s) by mid-week as the placement of the
surface high promotes cool, dry northerly flow. Rain chances through
week's end are very low to nil as all ensembles exhibit good
agreement on the high sinking into the New England region and
strengthening as it does so. If you're looking for more of a fall
feel, that should arrive to close out the week. Temps may moderate a
bit by next weekend.
&&
.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
Showers this afternoon were mainly focused from IDI to CKB, and
have largely shifted ewd with only residual meager buoyancy
remaining. Abundant low-level saturation exists for much of SW
PA and WV, with drying high pressure to the north and west.
For tonight, rapid clearing is likely as high pressure builds,
with relatively calm wind promoting quick cooling. This
combination of ingredients poses a higher-confidence forecast
for dense fog, with the primary uncertainty related to the wrn
edge of decreasing vsby.
The HREF distribution suggests a bimodal distribution for vsby,
with either dense fog or nothing resulting. For DUJ, LBE, MGW,
AGC, several hours of dense fog has a high (60-80%) probability
of occurrence, with earliest onset possible where rain occurred
earlier today. One limiting factor in these locations (MGW/LBE)
will be the departure of low-level clouds, which may slow the
onset of any fog.
For PIT/FKL/BVI, there is uncertainty in whether drying high
pressure or cooling/saturation will win the gradient battle, and
confidence in dense fog impacting these terminals is lower. So
prevailing vsby restrictions will be handled differently in
those TAFs, with 1-2SM featuring greater confidence, and any
drops below handled in TEMPO groups.
Fog and low cigs are expected to lift by mid-morning as light
wind ensues and dry air invades amid building high pressure.
Patchy river-valley fog will be possible late Sun night at some
terminals, but otherwise VFR conditions are anticipated once
tonight's fog dissipates Sun morning.
.OUTLOOK....
VFR returns amid high pressure Mon through mid week.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.
&&
$$
SYNOPSIS...Cermak/MLB
NEAR TERM...Cermak/Shallenberger
SHORT TERM...MLB
LONG TERM...MLB
AVIATION...Kramar
Source: PBZ issues Area Forecast Discussion (AFD) at Sep 27, 7:32 PM EDT (https://mesonet.agron.iastate.edu/p.php?pid=202509272332-KPBZ-FXUS61-AFDPBZ-AAA)
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