614
FXUS61 KPBZ 312201
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
601 PM EDT Fri May 31 2024

.SYNOPSIS...
Dry weather continues through the daytime on Saturday with
warming temperatures. Rain will return to the area Saturday
night and Sunday with crossing low pressure. Above normal
temperature and low probability showers and thunderstorms are
favored thereafter until the next system arrives mid to late
week.

&&

.NEAR TERM /THROUGH SATURDAY/...
KEY MESSAGES:

- Dry weather continues through Saturday.
- Temperatures will warm back above-normal on Saturday.
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The latest surface analysis shows high pressure centered across
the Upper Ohio Valley/Lower Great Lakes region. An upper ridge
was also building in from the Midwest, with 1000-500mb height
rises 60-90 meters across OH, PA and northern WV.

The ridge axis and surface high will shift eastward overnight,
turning flow more southerly and increasing warm/moist advection.
Cirrus is expected to increase through the night which, with
increasing humidity and warm advection, may help reduce the
efficiency of overnight radiational cooling. Overnight lows are
expected to run from the mid-40s to low-50s across the area,
though pockets in the upper 30s are possible north of I-80.

Cloud cover will increase on Saturday as the trough crosses from
the Mississippi Valley into the Ohio by late day. Warm advection
will boost afternoon temperatures back to just above average,
yielding area highs in the upper 70s to lower 80s.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
KEY MESSAGES:

- Showers and low probability thunderstorms arrive late Saturday
  through Sunday.

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The shortwave trough will near the area late Saturday, crossing
on Sunday. Generally light rain showers are expected with this
system Saturday night through Sunday. Probability for thunder
will be low as even 75th percentile SBCAPE values don`t exceed
100 J/kg, though the highest chance for any rumbles will be
Sunday afternoon. Showers will continue through the day until
the wave exits, becoming more scattered/isolated in the
afternoon. Lingering showers should gradually wane through the
evening and overnight. Flooding/severe threats should remain
minimal due to weak instability and weak deep-layer shear.

Cloud cover and ongoing showers will limit diurnal heating,
keeping Sunday afternoon highs ten or so degrees cooler than
Saturday.

&&

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

- Low probability showers and thunderstorms with above normal
  temperature likely to start the next work week.
- More widespread precipitation favored with mid to late week
  low pressure system.
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Ensembles generally favor gradual ridge building across the
Tennessee and Upper Ohio River Valleys Monday into Tuesday with
some shortwave movement to the north as troughing develops over
the northern Rockies. This should promote above normal
temperature and mainly dry weather for Monday as subsidence and
weak flow keep diurnally driven convection very isolated
(perhaps a thunderstorm or two in the ridges). The deviation
for that forecast could come Tuesday if shortwave movement is
more robust/deeper to the north Tuesday, which would increase
convective potential during the day (favored ECMWF route).
Either scenario would still be somewhat dependent on storm
evolution well west of the region and its impact on the larger
scale flow.

The synoptic pattern shows greater variation mid-week as not
all model solutions track the northern Rockies trough toward the
Great Lakes. Current model consensus, and this forecast
package, does trend toward the approaching/passing trough
scenario which would promote more widespread
showers/thunderstorms during the mid to late week period. If
ridging proves to be more stout ahead of the troughs approach,
that could delay the uptick in precipitation chances till next
weekend while maintaining a more dry and seasonable warm
pattern. Nonetheless, the variations remain too wide for any
discussion of severe or flooding threats at this time.

&&

.AVIATION /22Z FRIDAY THROUGH WEDNESDAY/...
VFR is expected through Saturday as high pressure moves east
across the Upper Ohio Valley region. Light and variable wind
tonight will veer to the SSE on Saturday, with speeds around 5
kt.

.Outlook...
Restrictions and showers/possible thunderstorms return Sunday
with a crossing trough of low pressure. Current ensemble
guidance indicate a 60-70% chance of MVFR on Sunday. MVFR to IFR
fog/stratus is possible Sunday night with low level moisture in
place. VFR returns later Monday and Tuesday under high pressure,
before a restriction and shower/thunderstorm potential returns
with a Wednesday cold front.

&&

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

&&

$$

SYNOPSIS...Rackley
NEAR TERM...WM/Rackley
SHORT TERM...Rackley
LONG TERM...Rackley/Frazier
AVIATION...WM