784
FXUS61 KPBZ 241740
AFDPBZ

Area Forecast Discussion
National Weather Service Pittsburgh PA
140 PM EDT Mon Jun 24 2024

.SYNOPSIS...
Dry and cooler weather is expected today under building high
pressure. Mainly dry and warmer weather is expected Tuesday,
before showers and thunderstorm chances return Tuesday night and
Wednesday with the approach and passage of a cold front.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
KEY MESSAGES:

- Seasonable temperatures and less humid today

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Surface high pressure will build across the Upper Ohio Valley
region today, as an upper trough crosses the NE CONUS. This will
result in dry and seasonable weather across the region. North to
northwest flow will advect drier air into the area through the
day, with dew points dropping into the 50s for many locations.

The CU rule and model soundings indicate a scattered cumulus
cloud layer will develop as convective temperatures are reached.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
KEY MESSAGES:

- Dry weather continues through Tuesday
- Shower and thunderstorms return Tuesday night through
  Wednesday evening
- Severe storms possible Wednesday

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High pressure will slide east of the region late tonight and
Tuesday, with the surface flow veering to the south. Rising
1000-500mb heights in flat ridging, and warm advection, will
drive temperatures back above average by around 5 degrees.

Differences exists in the operational models concerning the
development of an MCS upstream on Tuesday, and its eventual
track. Would expect initial development of an MCS along the
850mb low level jet late Monday night into early Tuesday across
the Midwest/Western Great Lakes region. Given the tendency for
MCSs to follow the 1000-500mb thickness pattern, and the best
instability remaining to our west, would expect the MCS to drop
southward across areas to the west of our forecast area, similar
to the scenario depicted in the 00Z NSSL WRF model output.
Maintained a dry forecast across the area on Tuesday at this
time.

Shower and thunderstorm chances will increase Tuesday night as
the next shortwave trough approaches, and ascent increase in
warm, moist advection. The shortwave, and its associated surface
cold front, will cross the area Wednesday into Wednesday
evening, with showers and thunderstorms expected. 0-6km shear is
expected to increase to near 40kt, according to the latest model
guidance. Model ensembles also indicate instability increasing
through the day with ML CAPE around 1000 j/kg. Plenty of
uncertainty still exists in the exact details of the mesoscale
environment, though some severe storms could be possible should
model progs verify. The Storm Prediction Center has placed a
portion of SW PA and nrn WV in a Slight Risk for severe storms
Wednesday, with the remainder of the area currently in a
Marginal Risk.

Showers and thunderstorms will end from W-E with FROPA Wednesday
night.

&&

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

- Dry weather through Friday
- Cooler Thursday, before a late week warmup
- Shower and thunderstorm chances return for the weekend
-------------------------------------------------------------------

Model ensembles indicate high pressure will build across the
region Thursday. Northwest flow should result in cooler and less
humid conditions. Ridging with rising 1000-500mb heights, and
warm advection, will result in dry weather and above average
temperatures on Friday.

The next shortwave trough and surface cold front is expected to
approach the region late Friday night and Saturday, returning
shower and thunderstorm chances to the forecast. These should
continue Saturday night into Sunday, as the front slowly crosses
the region.

Warm advection should result in above average temperatures on
Saturday, before reading return close to seasonable levels
Sunday as the cold front crosses.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
High probability of VFR under the influence of high pressure
through the TAF period. Diurnal heating/mixing will yield mostly
scattered 5-8kft CU and northwest wind gusts to 20kts this
afternoon.

Calm, clear sky may foster localized river valley fog Tuesday
morning, but dry air should keep probabilities more confined
south of KPIT.

The biggest uncertainty lays in the potential movement of a MCS
(storm system) through the Great Lakes region overnight into
Tuesday. Though the favored path is west of the region, there
remains a low probability for decaying showers and thunderstorms
to enter eastern OH to western PA between 15-20z Tuesday.
Probability of occurrence remains too low for TAF mention at
this time.

.Outlook...
Assuming westward MCS path, VFR is likely into Tuesday night
before a weak shortwave trough fosters showers and thunderstorms
(with associated restrictions) Wednesday into Thursday morning.

High confidence in VFR under the influence of high pressure
Thursday into Saturday morning before the next low pressure
system passes.

&&

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

&&

$$

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