906
FXUS61 KPBZ 040557
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
157 AM EDT Wed Jun 4 2025

.SYNOPSIS...
Dry and warmer weather is expected through Wednesday under high
pressure. Showers and thunderstorm chances return Thursday with
an approaching cold front. This front is expected to drift
southward through Saturday, keeping unsettled weather in the
forecast.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
KEY MESSAGES:

- Dry and mainly clear overnight
---------------------------------------------------------------

Late evening update...
No major changes to the overnight forecast. Removed the mention
of haze, with sfc vsbys unrestricted. A ridge will maintain the
dry weather overnight, with lows around 5 degrees above average.

Previous discussion...
No major changes to the ongoing forecast this evening. Have
seen some degradation to air quality both with deeper mixing
today and as smoke nearer to the surface advects north. Values
have touched levels such that sensitive groups should use extra
precaution if spending prolonged periods outdoors and continue
to monitor the forecast levels.

Meteorologically, this will be at least day one of eastern
ridging, with surface high pressure to the east. This pattern of
subsidence should stave off cloud coverage, through low-level
southwest flow overnight is expected to increase moisture,
keeping low temperatures around 5 to 10 degrees above average.
Chances of staying above 70F are 10% to 30% along the ridges
and in the Ohio Valley.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY NIGHT/...
KEY MESSAGES:

- Hot with moderate heat risk for valleys / urban areas Wed.
- Storm chances in eastern Ohio Thursday.
----------------------------------------------------------------

Height rises continue into Wednesday, with heights topping out
as high as 588dm to 590dm, particularly southeast of
Pittsburgh. While this might allude to temperatures pushing 90F,
there may be enough moisture return Wednesday morning to
support a cumulus deck and some uncertainty with smoke
concentrations and their potential to lower highs a degree or
two from what they would have otherwise.

CIPS analogs maintain around a 70% chance of temperatures
topping 85F, with a <10% chance of 90F. HREF probabilities have
backed off with chanced of >85F, only exceeding 50% in valley
and urban areas. All in all, we would expect urban heat islands
and river valley to be the warmest, where a moderate heat risk
is forecast, with the hottest hours Wednesday afternoon. High
clouds increase overnight ahead of the next wave, increasing
insolation in southwest flow. This has the potential for lows to
be 10F to 15F above normal.

By Thursday, there should be enough moisture return to allow for
increased convective activity, with the highest rain chances
along the CAPE gradient associated with the approaching front.
Frontal progression is expected to be slow, so any storms
Thursday would have to fire off the front or subtle forcing,
creating a domino effect of gust fronts and new updrafts,
highest for eastern Ohio. There is a low chance the mountains
may be in play too with ridgetop convergence. The 50th
percentile CAPE has ~1000 J/kg, but shear remains low. With dry
air aloft (500-600 mean DCAPE, 900 90th percentile DCAPE), this
may signal a downburst wind threat with isolated flooding
concerns possible. Concerns wain overnight with the loss of
heating.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
KEY MESSAGES:

- Slow frontal passage this weekend with rain and storm chances.
-------------------------------------------------------------------

A good deal of what each day looks like Friday through Sunday
will depend on the exact timing and location of the front. Most
ensemble clusters signal at this slow crossing, where the front
is across the area Friday and into Saturday. Subtle differences
in timing wash out the ensemble mean instability a bit,
suggesting decreases each day, but more likely, the environment
will be a bit similar each day, primarily governed by diurnal
storms with as least a chance of downburst wind and hail
threats. Any time we have a stalled boundary, flooding also
remains a concern in training, especially with 1-1.5" PWATS. The
exacts of this will need to continue to be more flushed out.

Clustered ensembles remain in good agreement save an outlier of
a slightly more progressive front, drier, and cooler conditions
Sunday (11% of membership). Otherwise, there is good confidence
in eastern troughing by the middle of next week with
uncertainties in timing, amplitude, and just how fast we return
to ridging late week. Much of the temperature spread if from
the mid 70s to mid 80s for highs.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
VFR will continue with high pressure through the TAF period.
Main change with the 06z package was to remove 6SM HZ from all
sites. Latest guidance indicates near-surface smoke density will
be less Wednesday than on Tuesday. Little to no vis restrictions
were observed on Tuesday, so that is likely to remain the case
on Wednesday. High level smoke/haze will continue.

Wind remains generally light and southwesterly through the
period. The exception is possible gusts to 20kt at FKL with
daytime mixing.

Outlook...
The next potential impact period will be on Thursday
when shower and thunderstorm chances increase (and restrictions
mainly tied to convection) as a series of shortwaves cross over
the ridge axis.

&&

.PBZ WATCHES/WARNINGS/ADVISORIES...
PA...None.
OH...None.
WV...None.

&&

$$

SYNOPSIS...Milcarek
NEAR TERM...WM/MLB/Milcarek
SHORT TERM...Milcarek
LONG TERM...Milcarek
AVIATION...Rackley/88