PBZ issues Area Forecast Discussion (AFD) at Oct 24, 7:32 AM EDT496
FXUS61 KPBZ 241132
AFDPBZ
Area Forecast Discussion
National Weather Service Pittsburgh PA
732 AM EDT Fri Oct 24 2025
.SYNOPSIS...
Lake-effect showers taper Friday into Saturday. Frost and
freeze concerns linger each morning. Large forecast uncertainty
develops mid-to-late next week.
&&
.NEAR TERM /THROUGH TONIGHT/...
KEY MESSAGES:
- Rain showers north of I-80 for much of the period; shower
chances peak in the afternoon elsewhere.
- Frost and freeze concerns return tonight.
---------------------------------------------------------------
The current trajectory of the frost advisory and freeze warning
remains on track through daybreak with observational clearing
and calming winds.
North of I-80, lake effect showers will continue with adiabatic
profiles and northwest flow over the comparatively warm Lake
Erie waters. This will allow shower chances to continue through
the morning in areas that have already seen bouts of rain over
past days. Elsewhere, daytime mixing will likely cause the
development of a broken cumulus deck in a continued nealy-
saturated 850mb to 700mb layer. Shallow saturation may once
again allow the development of scattered daytime showers south
of I-80 with probabilities higher the farther north you go with
lake influence on saturated layer depth. Convection will remain
shallow with a strong subsidence inversion above 3km, so any
showers will likely be brief and light.
Upper ridging and a loss of mixing will ensue overnight, likely
clearing much of the broken cumulus decks outside of the I-80
corridor. Probabilities of cloud cover decrease the farther
south you go, as do chances of wind. Thus, radiative cooling
and a frost/freeze is most likely tonight south of I-70 (50% to
70% chance of freeze), and possible south of I-80 (30% to 50%
chance of freeze) depending on the presence of clouds. North of
I-80, chances of a freeze are lower with cloud cover more
likely. These decisions will be made on the day- shift as to not
conflate active products or and county frost/freeze program
cancellation.
&&
.SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/...
KEY MESSAGES:
- Low chances of showers north of I-80.
- Seasonable elsewhere with frost/freeze chances.
----------------------------------------------------------------
Frost/freeze chances linger into the early hours Saturday, but
mostly clear skies in the morning south of I-80 will allow
heating to bring highs up close to seasonal normals, though most
will fall slightly below the mark. Continued upper ridging will
dry out the depth of the near-saturated, near-surface column,
but there may still be enough moisture for a very shallow
cumulus deck. In the I-80 corridor, continued, light NW 850mb
wind will likely keep the moisture depth slightly higher,
allowing a small chance of showers persisting through the
afternoon. South of I-70, high clouds may encroach on a passing
southerly disturbance.
By Saturday night, most low clouds are forecast to dissipate but
there may be high clouds for the southern half of the forecast
area. Thus, contrary to the night before, frost/freeze chances
remain higher north of Pittsburgh, where 40% to 60% chances of a
freeze are currently forecast.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
KEY MESSAGES:
- Mainly dry through early next week.
- Low forecast confidence mid-to-late week with a complex
interaction of upper lows.
-------------------------------------------------------------------
Though high clouds may be possible on a passing southern
disturbance Sunday into Monday, there is relatively high
forecast confidence rain chances will be limited by high
pressure and subsidence with highs near normal and frost/freeze
chances each night.
By mid-week there has been increasing confidence in the
presence of a closed 500mb low off the coast of New England The
strength and location of this will have large implications on
the extended period.
The most likely scenario, with roughly 50% of LREF membership,
is that the aforementioned system that passes to the south feels
the influence of the closed low, forcing it to retrograde under
a northern blocking ridge into an incoming trough. This would
result in east coast cyclogenesis and eastern CONUS troughing.
Locally, this would lead to strengthening northerly flow under
lake influence that would provide showers, whereby the high
terrain to the east may see more rain under the influence of the
coastal surface low itself.
The two drier and warmer scenarios would be related to the
potential development of a midwest ridge between the closed low
and incoming through, forcing any influence from the low to
remain more confined to the coast. Additionally, the incoming
trough itself could cut-off and dive south, enforcing eastern
ridging mid-week, and delaying rain chances until the cut-off
drifts northeast late-week.
For these reasons, the complex forecast remains low-confidence
in the middle-to-late week period. Highs could be anywhere from
the upper-50s to the mid-40s. Rain could also be anywhere from
a light accumulation to up to a couple inches. Much more will be
known as the event draws nearer.
&&
.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
A stratocu deck continues to plague the area this morning,
though most terminals are currently sitting at VFR and should
remain there through the period. The exception continues to be
north of I-80 (FKL/DUJ) where lake-effect showers and locally
LIFR ceilings are ongoing, and along the ridges (LBE) where weak
upslope flow is allowing MVFR ceilings to linger. Improvement will
be gradual for these locations (especially north of I-80), but
by afternoon most of the area should be at VFR. While the bulk
of shower activity will remain limited to areas along and north
of I-80, once again can't rule out a few scattered light showers
or sprinkles making their way farther south to PIT/AGC/LBE this
morning and afternoon. Winds continue to trend lighter than
recent days (7 to 10 knots out of the west-northwest), though
infrequent gusts to 15 knots remain possible during peak mixing
hours this afternoon.
As decoupling occurs after sunset, cloud cover south of I-80 is
expected to diminish between 00Z to 04Z Saturday. North of I-80
(FKL/DUJ), light northwest flow should continue to support
lake-effect stratocu with ceilings at low-end VFR or MVFR,
though the chance for showers will finally start to decrease as
moisture in the boundary layer becomes more shallow.
.OUTLOOK...
Areawide VFR returns over the weekend as the trough axis shifts
east and weak ridging builds overhead. Another system could
return rain and restriction chances from the south early next
week.
&&
.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...Frost Advisory until 9 AM EDT this morning for PAZ029-031.
OH...Frost Advisory until 9 AM EDT this morning for OHZ039-040-
048>050-059.
Freeze Warning until 9 AM EDT this morning for OHZ057-058-068-
069.
WV...Frost Advisory until 9 AM EDT this morning for WVZ001>004-012-
021-509-510.
Freeze Warning until 9 AM EDT this morning for WVZ511>514.
&&
$$
SYNOPSIS...Milcarek
NEAR TERM...Milcarek
SHORT TERM...Milcarek
LONG TERM...Milcarek
AVIATION...Cermak
Source:
PBZ issues Area Forecast Discussion (AFD) at Oct 24, 7:32 AM EDT---------------
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