Severe Thunderstorm Warning 299, NWS Pittsburgh, PA

Area Forecast Discussion
National Weather Service Pittsburgh PA
441 PM EDT Mon Sep 13 2021

.SYNOPSIS...
Shower and thunderstorm chances are expected through this evening
north of Interstate 80. Otherwise, warm and dry weather will continue
until more widespread showers and thunderstorms move across the
region with a Wednesday cold front.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
Afternoon Update: SPC Mesoanalysis indicates high CAPE values
coincident with favorable wind shear north of I80 this afternoon.
This area will be monitored for convection as a shortwave trough
allows for forcing for ascent while lapse rates increase. If cells
develop, damaging wind is the primary threat. The window in which
convection is possible will narrow, as peak heating is beginning to
cease and shortwave is propagating eastward. Previous:

Shower and thunderstorms chances should continue through this evening
north of I 80 as a cold front moves slowly south across NW PA, and a
shortwave approaches. Most of the rain is expected to stay north of
the forecast area where better upper support is progged. Capping warm
air aloft should also limit the thunderstorm potential, though lift
in the vicinity of the front could still result in a few
showers/storms. A strong storm is possible with marginal shear and
instability, but the warm air aloft should be a limiting factor in
this potential.

Otherwise, dry weather is expected through tonight under shortwave
ridging south of the front. Warm temperatures should continue
tonight, with lows around 10 degrees above average.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH THURSDAY/...
Ridging/SW flow aloft should push the front back to the north
Tuesday, with mainly dry weather expected. A shortwave trough, and
its associated sfc cold front, is expected to approach the Upper Ohio
Valley region Tuesday night, with shower chances increasing,
especially late.

More widespread showers are expected Wednesday as the trough and sfc
cold front cross the region. Marginal shear and instability could
result in a severe thunderstorm potential Wednesday afternoon and
early evening, though cloud cover could be a limiting factor in the
amount of destabilization and the resulting severe weather potential.
Rain chances should then diminish Wednesday night as the front
completes its passage.

Models differ on the positioning of a souther stream trough Thursday,
and it moves slowly NE toward the region. Continued with low chances
for showers attm, using a blended model solution to account for the
uncertainty. Above average temperatures are expected to continue
through the period.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
The southern stream trough should continue to drift across the Ern
CONUS through Saturday, with low chances of showers and
thunderstorms continuing across the Upper Ohio Valley region.

Model ensembles then indicate a ridge should build across much of the
Ern CONUS through the rest of the weekend, with dry and warm weather
expected.

&&

.AVIATION /21Z MONDAY THROUGH SATURDAY/...
Widespread MVFR stratocu is expected to persist through early aftn
as a swd sagging frontal boundary has created sufficient lift in the
moist, but stable boundary layer for that formation. An upstream
shortwave is expected to lift the boundary nwd again later today
before spawning some isold, to sct shra/tsra this eve near the I 80
terminals. VFR is thus expected to return until that convection
potential affects those ports.

.Outlook...
Restrictions are then likely with a Wed cold front.

&&

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

&&

Hazardous Weather Outlook...UPDATED
National Weather Service Pittsburgh PA
126 PM EDT Mon Sep 13 2021

OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023-029-
031-073>076-WVZ001>004-012-021-509>514-141730-
Tuscarawas-Carroll-Columbiana-Coshocton-Harrison-Jefferson OH-
Muskingum-Guernsey-Belmont-Noble-Monroe-Mercer-Venango-Forest-
Lawrence-Butler-Clarion-Jefferson PA-Beaver-Allegheny-Armstrong-
Indiana-Washington-Greene-Westmoreland-
Higher Elevations of Westmoreland-Fayette-
Higher Elevations of Fayette-Hancock-Brooke-Ohio-Marshall-Wetzel-
Marion-Monongalia-
Ridges of Eastern Monongalia and Northwestern Preston-Preston-
Eastern Preston-Western Tucker-Eastern Tucker-
126 PM EDT Mon Sep 13 2021

This Hazardous Weather Outlook is for east central Ohio, western
Pennsylvania, and northern West Virginia.

.DAY ONE...This afternoon and tonight.

An isolated severe thunderstorm is possible through this evening
north of Interstate 80.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

Scattered severe thunderstorms are possible Wednesday afternoon and
evening with a crossing cold front.

.SPOTTER INFORMATION STATEMENT...

Weather spotters are encouraged to report significant weather
conditions according to Standard Operating Procedures.

Special Weather Statement
National Weather Service Pittsburgh PA
518 PM EDT Mon Sep 13 2021

PAZ008-132145-
Venango PA-
518 PM EDT Mon Sep 13 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTHERN VENANGO COUNTY THROUGH
545 PM EDT...

At 518 PM EDT, Doppler radar was tracking a strong thunderstorm near
Guys Mills, or 13 miles east of Meadville, moving east at 25 mph.

HAZARD...Wind gusts up to 40 mph and pea size hail.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects. Minor hail damage to vegetation is
         possible.

Locations impacted include...
Cooperstown, Pleasantville, and Oil Creek State Park.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 4149 7957 4148 8000 4150 8000 4150 7998
      4151 7998 4151 7996 4156 7991 4156 7989
      4157 7989 4157 7987 4158 7987 4159 7985
      4160 7985 4160 7983 4162 7983 4162 7956
TIME...MOT...LOC 2118Z 266DEG 23KT 4160 7990

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...40 MPH