921
FXUS61 KPBZ 011637
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
1237 PM EDT Sat Jun 1 2024

.SYNOPSIS...
Showers will return to the area late tonight into 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 TONIGHT/...
KEY MESSAGES:

- Dry weather continues through this evening before rain moves
  in from the west late tonight.
- Warmer temperatures in the upper 70s and lower 80s are
  expected this afternoon.
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Upper analysis shows the ridge axis crossing overhead this
morning as surface high pressure shifts over the east coast.
This will keep dry weather in the forecast through most of the
day until rain returns late tonight.

Partly/mostly sunny skies under cirrus this morning will become
more cloudy through the day with increasing warm/moist advection as
the ridge shifts east in response to the approach of a weakening
shortwave trough. Despite increasing cloud cover, warm
advection will boost afternoon temperatures to just above
normal, pushing high temperatures into the upper 70s to lower
80s.

Mostly light showers will arrive late tonight and Sunday morning
ahead of the weakening shortwave. Recent model trends have
slowed onset of showers slightly, putting onset of rain in the
eastern Ohio zones likely after midnight and into the Pittsburgh
metro near sunrise Sunday. Stable overnight conditions and
marginal shear should preclude lightning development.

&&

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

- Showers and low probability thunder expected Sunday before
  tapering off during the evening.

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Gradual progression of the generally weakening shortwave trough
is expected Sunday, with the system generally exiting late
Sunday night. The associated precipitation areas will progress
across eastern Ohio during the morning hours then through
western Pennsylvania during the afternoon and evening. The
environment will feature minimal instability due to excessive
cloud cover (less than 500 J/kg SBCAPE focused mainly south of
I-70) and weak shear; this will limit storm strength (limited
severe threat) and rainfall rates/updraft organization (limited
flooding threat). The lack of stronger surface forcing and the
decaying dynamics of the shortwave will also create more of a
scattered coverage appearance, meaning some locations may see
little to no rain.

Dry weather should return by Sunday night with the loss of
daytime heating and exiting of the shortwave, with any lingering
showers confined to upslope Laurel Highland zones. The lack of
notable dry advection behind the system could make fog a
potential overnight impact, depending on the degree/quickness of
cloud clearing.

&&

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

- Low probability showers and thunderstorms with above normal
  temperature likely to start the next work week.
- Increasing precipitation chances accompany a mid to late week
  low pressure system that will cause falling temperature.

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Subtle ridging stretching from the lower Tennessee River Valley
to the upper Ohio River Valley Monday is likely to promote dry
weather and slightly above average temperature. The probability
for showers and thunderstorms should be low and generally
confined to the higher terrain where better moisture and terrain
convergence may lead to an isolated afternoon storm. Little
change in the broad synoptic flow is expected for Tuesday, which
will promote above normal temperature and dry weather. That
said, there remains a scenario that convective evolution to the
west could push far enough east to increase precipitation
chances late Tuesday into Wednesday morning.

Ensemble means continue to favor the eastward progression of an
upper level trough into the western Great Lakes Wednesday. This
scenario would provide increasing large scale ascent/forcing to
promote more widespread showers and thunderstorms Wednesday
into Thursday. However, an alternate but plausible outcome is
that more staunch ridging will either delay trough arrival or
deflect its passage farther north; this would delay the next
precipitation chances while maintaining above normal
temperature.

Confidence is higher for general troughing to move over the
Great Lakes region by Friday that would promote periods of
showers and thunderstorms and downward trending temperature.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...
VFR will continue as into the evening as high pressure slowly
edges east of our region. Mid and upper clouds will dominate
through then evening hours, slowly lowering and thickening with
time.

An approaching, weakening shortwave trough will push some light
rain showers into eastern Ohio after 06Z, with coverage slowly
expanding across the Upper Ohio Valley through the morning. NBM
probabilities of MVFR ceilings are 60-80% areawide after 12Z,
and have included that thinking in the TAFs. Best chance of
dropping to IFR is at ZZV according to the same blend, with
lesser chance to the east. This seems reasonable, as daytime
mixing may prevent ceilings that low later in the morning.

Wind will remain light through the TAF period, with a slow veer
from southeast to southwest with time.


.Outlook...
Restrictions and showers/possible thunderstorms continue into
Sunday evening as the shortwave crosses. MVFR to IFR fog or
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/Frazier
NEAR TERM...Rackley
SHORT TERM...Rackley
LONG TERM...Rackley/Frazier
AVIATION...CL/88