Severe Thunderstorm Warning 296, NWS Pittsburgh, PA

Area Forecast Discussion
National Weather Service Pittsburgh PA
401 PM EDT Wed Sep 11 2019

.SYNOPSIS...
Warm and humid conditions will be in place through Friday, with
periodic chances for showers and thunderstorms. A crossing cold front
will filter in drier air in high pressure for the weekend.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Strong daytime heating in a buoyant airmass, combined with lift from
an encroaching Great Lakes trough has led to the development of
scattered showers and thunderstorms this afternoon.

Cooling mid-levels associated with the upper trough, combined with
strong surface heating suggests steep lapse rates, with mixed layer
CAPE values progged between 1500-2000 J/kg. These values are realized
in AMDAR soundings out of KPIT. Recent soundings and SPC RAP
analysis also suggest sufficient dry air at mid-levels supporting a
damaging wind threat given stronger updrafts. Hail will also be
possible given the deep CAPE profile, although the lack of shear and
warm layer exceeding 12,000ft should keep it mostly sub-severe.

The severe threat should wane with the loss of daytime heating this
evening, though, periodic showers remain possible through the night
given a very warm, humid airmass and continued shortwave support
associated with the aforementioned trough. Summerlike minimums in
the mid and upper 60s are forecast.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
On Thursday, a weak cold front is progged to push south across the
region, although its progress will likely be hindered by the still-
strong ridge in place across the southeast CONUS and lack of jet
support. This boundary should serve as a mechanism for additional
shower and thunderstorm development during the afternoon and evening.
Lingering morning clouds should hinder destabilization, limiting the
overall severe threat.

The boundary is anticipated to lift north as a warm front as the
southeast ridge expands north once again on Friday. Deepening low
pressure across the upper Midwest will push a stronger cold front
through the region Friday night. Numerous showers and thunderstorms
should accompany this system, and likely PoPs were maintained.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
The front will continue its passage on Saturday, with rain chances
ending from west to east during the day. A brief period of zonal flow
will be in place Sunday, with high pressure providing dry weather but
still above-normal temperatures.

Early next week, ridging should become established again, although
models differ on where the axis sets up. This may have implications
for PoPs, as ripples riding over the ridge may provide rain chances.
Chances were kept quite low for now due to uncertainty. In any case,
our September warm spell looks set to continue.

&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
Medium confidence forecast save for the 6Z-14Z time window where
confidence is low given CIGS could be lower than forecast.

CU has developed and storms are not that far behind as of the 18Z
hour. Things are coming together for a line of showers and storms to
develop across northeast Ohio into northwestern Pennsylvania then
move southeast through the afternoon hours. Activity will wane with
the loss of heating between 0Z-2Z. Continued mention of VCTS at all
terminals through 3Z save for FKL and DUJ where any storm should be
out by 22Z. Would not be surprised for a brief drop to IFR vis in any
storm, but did not include any tempos at this time. Do not expect
showers during the night through the end of the forecast time frame.

After the storms fizzle out, what if any fog will develop during the
predawn hours? For now, thinking it will be more of a stratus event
given we won't totally clear out. Dropped CIGS to low end MVFR at FKL
and DUJ, but those could be lowered to IFR with future forecasts,
elsewhere ran with BKN015-025 around daybreak through mid morning.
Moisture is locked in at low levels with the boundary lingering
around.

Wind will light from the west. We could see gusts nearing 20 knots
for a short time period this afternoon.

.Outlook...
Isolated storms are possible Thursday while they will more widespread
restrictions Friday night into Saturday with a cold front.

&&

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

&&

Hazardous Weather Outlook
National Weather Service Pittsburgh PA
303 PM EDT Wed Sep 11 2019

MDZ001-OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023-
029-031-073>076-WVZ001>004-012-021-509>514-121915-
Garrett-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-Westmoreland Ridges-
Fayette-Fayette Ridges-Hancock-Brooke-Ohio-Marshall-Wetzel-Marion-
Monongalia-Ridges of Eastern Monongalia and Northwestern Preston-
Preston-Eastern Preston-Western Tucker-Eastern Tucker-
303 PM EDT Wed Sep 11 2019

This Hazardous Weather Outlook is for western Maryland, east
central Ohio, northwest Pennsylvania, southwest Pennsylvania, west
central Pennsylvania, western Pennsylvania, northern West Virginia
and northern panhandle of West Virginia.

.DAY ONE...This afternoon and tonight.

Scattered thunderstorms will continue through tonight, with isolated
incidents of severe weather possible. The primary hazard will be
damaging wind, however small hail and localized heavy rainfall
cannot be ruled out.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

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