425
FXUS61 KPBZ 222242
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
642 PM EDT Thu May 22 2025

.SYNOPSIS...
Upper low pressure center will remain over the Great Lakes
today and tomorrow keeping precipitation chances in the forecast
through the beginning of the weekend. High pressure will
finally bring some dry weather by Sunday.

&&

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

- Numerous showers this evening will become more isolated to
  scattered overnight
- Little diurnal temperature change expected
-------------------------------------------------------------------

Scattered to numerous light rain showers will continue this
evening due to mix of vorticity movement within upper troughing
over the eastern Great Lakes and diurnally induced weak
instability. The mixed near surface layer will also allow for
occasional gusts between 20 to 30 mph (mainly in the higher
terrain).

The loss of diurnal heating tonight, as minimal as it may be,
will transition the region to more isolated to scattered light
rain (or drizzle) showers that are generated primarily on jet
induced lift as additional shortwaves round the base of the
upper trough. Abundant cloud cover and residual post-frontal
mixing should limit typical diurnal cooling and keep the range
of area temperature within 5-10 degrees of the current afternoon
readings. Temperature falls may be more prominent late in the
overnight period for the far eastern OH zones where some dry
advection and subsidence could briefly clear cloud decks to
allow greater radiational cooling.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
KEY MESSAGES:

-Rain showers will persist Friday and Saturday, though coverage
 will decrease.
-Well below normal temperatures continue.
----------------------------------------------------------------

Ensemble guidance and cluster analysis remains in good agreement
on the general progression of the trough through this period
with the low center shifting eastward into Saturday. While that
will mean that the deeper moisture will shift north and east,
we will remain in NW flow for the bulk of the period. With
850hpa temperatures close to 0C, lake enhanced and upslope rain
showers are likely. Coverage will be at it`s greatest during the
daylight with fairly modest diurnal heating. Increasing
subsidence will lend to drier conditions generally south of
Pittsburgh as we go into Saturday. Confidence in showers will be
highest north of I-80 but some differences in the evolution of
the shortwave ridging maintain at least low shower chances
through as far south as Pittsburgh.

Sunday should be the best chance for dry weather areawide and
also the day we see the most amount of sunshine.

Cold advection will keep temperatures 10-15 degrees below
seasonal averages Fri and Sat, and 5-8 degrees Sunday though
some moderation is expected with with peaks of sun through the
cloud deck.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
KEY MESSAGES:

- The return of unsettled weather through midweek.
- Moderating temperatures but still below normal.
-------------------------------------------------------------------

A fairly active period in place through midweek as models are
coming into better agreement on the return of precipitation late
Monday into Tuesday as a southern stream low pressure system
lifts toward the upper Ohio Valley. While the models seem to be
handling this particular system well, the broader upper pattern
does have some differences. Cluster analysis through this
period varies on the depth and speed in which an upper low over
the northern central CONUS reinforces the broad troughing over
the Great Lakes. The general trend is to keep conditions showery
with temperatures remaining below average.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
Low VFR to MVFR ceilings are likely to initially prevail amid
cold advection underneath upper troughing and waves of scattered
light rain showers. Subsidence and a moist boundary layer may
support more widespread cig lowering to MVFR/localized IFR
heights between 04z-11z but timing of lowest cigs and exact low
cig height is a bit uncertain due to a relatively mixed boundary
layer that can cause cig fluctuations.

Dry advection and subsidence will attempt to erode stratocu near
ZZV around sunrise Friday, but diurnal heating should ensure all
TAF sites remain within bkn deck. This heating/mixing will
result in improving cigs toward VFR by 00z (save for FKL/DUJ)
but may induce isolated early afternoon rain showers.

Outlook...
Dry weather and VFR is initially favored overnight Friday, but
residual NW flow and a potential weak front may return low
probability rain showers and MVFR cig chances as far south as
KPIT/KAGC/KLBE to start the day Saturday.

High confidence in areawide VFR by Saturday night into the
majority of Sunday under the influence of high pressure and
rising heights aloft. An active pattern featuring restrictions
and rain is likely to return to the region by mid week.

&&

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

&&

$$

SYNOPSIS...34
NEAR TERM...Frazier
SHORT TERM...34
LONG TERM...34/Shallenberger
AVIATION...Frazier