706
FXUS61 KPBZ 251150
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
750 AM EDT Sat May 25 2024

.SYNOPSIS...
Dry weather is expected through the morning. The chance for
showers and strong to severe thunderstorms will increase this
afternoon and evening. Sunday is expected to be mostly dry
under high pressure, but thunderstorms will returning Sunday
night into Memorial Day. As we flip the calendars to June,
temperatures fall back to just below normal.

&&

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

- Dry through much of the morning hours
- Increasing chances for strong to severe storms this
  afternoon/evening with a crossing shortwave
- Hail, damaging wind, and excessive rainfall will be the main
  threats
  _____________________________________________________________

Weak ridging has briefly built overhead through the overnight.
This will begin to flatten and shift east through the morning
hours, resulting in continued dry weather through much of the
morning. Meanwhile, stacked low pressure will eject out of the
upper Midwest today with a trailing front sweeping across the
Ohio Valley this afternoon and evening. Warm, moist advection
has already begun this morning as the long-lingering front
across our southern area lifts northward as a warm front. A few
showers with perhaps a rumble of thunder may develop along this
boundary later in the morning. However, more organized
scattered to widespread convection is not expected to develop
until mid-afternoon as the cold front slowly advances into Ohio.

Afternoon temperatures in the low/mid 80s and dew points in the
mid/upper 60s will boost MUCAPE values above 2000 J/kg by
mid/later afternoon. Hail and strong wind potential with
stronger/taller storms will be maximized in the several hours
before sunset. The SPC marginal outlook continues for the entire
area.

By this evening, the threat for severe weather will likely shift
from a hail/wind threat to an excessive rainfall and flash
flooding threat, particularly south and southeast of Pittsburgh
where the front will come to a crawl through the overnight
hours. Storms focused along this boundary may produces excessive
rainfall over areas already primed for localized flash flooding.
Farther north, convection will wane through the evening hours.

&&

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

- Dry weather returns through much of Sunday, with
  thunderstorms returning in the evening.
- Strong to severe storms are possible late Sunday night,
  primarily across eastern Ohio.

_____________________________________________________________

Brief ridging builds once again on Sunday, with dry weather
expected through much of the day.

Low pressure will develop across the Plains tonight, lifting
across the Great Lakes by Monday. Moisture will advance across
the region with southwest flow Sunday evening into Monday,
though the latest guidance has slowed the progression of this
system and the eventual onset of convection across the region.
CAMs confine any late afternoon convection to the ridges, with a
pre-frontal line of thunderstorms not nearing our forecast area
until midnight. This timing is not typically favorable for
severe weather in our area, and weakening is expected as these
storms cross into the area. However, a strengthening 30-40kt LLJ
across the area late Sunday night may help maintain several
stronger storms with damaging wind and/or large hail into
eastern Ohio. SPC has highlighted this risk with a Marginal Risk
for that area, keeping the Slight Risk farther west.

Showers and thunderstorms will continue on Monday, with slow cold
frontal passage slowly diminishing rain chances from west to
east into the evening. Daytime surface heating may contribute to
and environment favorable for severe thunderstorm development,
particularly on Monday afternoon. SPC has outlooked the area in
a Marginal Risk.

&&

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

- Near normal to below average temperatures are expected under
  an elongated trough over the Northeast.
____________________________________________________________

Another couple of rainy days look to be in store as a secondary
cold front crosses the region Tuesday and low pressure crossing
to our north on Wednesday. Ensembles then suggest a pattern
change as deep upper troughing develops over the eastern CONUS
with ridging over the Plains. Broad surface high pressure should
finally keep the area dry while temperatures fall back towards
seasonal average.

&&

.AVIATION /11Z SATURDAY THROUGH WEDNESDAY/...
High confidence forecast (95%) of VFR through the evening hours
and no precip through 16Z. Confidence falls back into the
40-50% range during the afternoon and evening given uncertainty
with thunderstorm placement.

VFR weather with yield to a developing cumulus field by midday
then as a shortwave trough passes during the afternoon hours,
this will kick off showers and thunderstorms. Brief IFR vis are possible
with the heavier downpours, but it won`t last long /less than
30 minutes/, while CIGS could drop into the MVFR category.

Timing is tricky, so did the best to time in the afternoon
hours, where the highest probs exist and aligns well with the
CAMs.

Any airport that sees a storm this afternoon - early evening
should see at least MVFR fog and some places could even see IFR
fog, but will use later forecasts to fine tune forecasts.

.Outlook...
High pressure and subsidence should promote VFR and dry weather
late Saturday night into Sunday. Fog may develop before dawn
Sunday in rain-soaked locales that experience overnight
clearing.

Thunderstorm probabilities increase overnight Sunday into
Monday as a more robust low pressure system moves through the
Great Lake region. A pattern shift thereafter will introduce
periodic precipitation chances and potential for more prolonged
cig restrictions.

&&

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

&&

$$

SYNOPSIS...Rackley
NEAR TERM...Rackley
SHORT TERM...Rackley
LONG TERM...Hefferan/Rackley
AVIATION...Shallenberger/McMullen