Severe Thunderstorm Warning 137, NWS Pittsburgh, PA

Area Forecast Discussion
National Weather Service Pittsburgh PA
235 PM EDT Thu Jun 27 2019

.SYNOPSIS...
Isolated to scattered showers and thunderstorms are expected once
again on Friday in this typical summer pattern. Better rain chances
are expected this weekend with a passing front.

&&

.NEAR TERM /THROUGH TONIGHT/...
A weak boundary is located just to the north of Pittsburgh in
southwest PA, showing up on visible satellite loops as well as in the
pressure/dewpoint fields. CAPE has already built near and to the
south of the boundary, with values already approaching 2000 J/kg.
Scattered thunderstorms are firing across the region, concentrated
over the hear the CWA initially, with a weak mid-level shortwave
providing support for lift. Shear overall is weak, and thus do not
expect much in the way of storm organization outside of cold pool
interactions. Nevertheless, given the strong CAPE, dry air aloft, and
steep low- level lapse rates, strong to damaging downburst wind
appears to be a possibility. Cannot rule out hail as well, with model
soundings showing more favorable CAPE aloft than earlier.

Activity should rapidly fade this evening with the loss of
instability and the departure of the upper wave.  Clearing sky and
light wind may also allow for patchy valley fog formation,
especially in locations that receive rain today. A warm and humid
night is figured, with temperatures a few degrees above climatology.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
Another round of isolated thunderstorms is possible Friday
afternoon, as another weak shortwave passes. This disturbance will
take a more northerly track than the one today though, and there are
also indications of warmer mid-level air that could hinder
development. Will keep PoPs a bit lower than today as a result, in
the 20/30 range. Coverage will once again diurnally decrease during
the evening.

Strengthening Plains ridging will induce falling heights over our
area in response on Saturday. Better coverage of showers and storms
is expected that afternoon with cooler air aloft and still
sufficient instability, and as a front starts to sink in from the
Great Lakes. Strong to marginally severe storms appear possible once
again with favorable lapse rates.  Rain chances will continue
through Saturday night and into Sunday as the front crosses the
region, with rain chances decreasing from south to north with time
behind the boundary as drier air sinks in.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Ridging over the southeast CONUS will dominate this period, with the
axis driving slowly eastward with time. At this time, it appears our
region will be set up on the northern periphery of this feature, with
a period of northwest flow aloft at least during the early part of
next week. This pattern would favor a few rounds of showers and
thunderstorms, with no single day guaranteed to be dry through the
extended period. Temperatures will remain seasonably warm.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
Iso to sct thunderstorms will move east this aftn/eve ahead of a
weak shortwave trough and be fueled by daytime heating. Best chances
for terminal impact will be across portions of eastern OH into
western PA coinciding with best lift and greatest instability. Any
storm that moves over an airfield could briefly reduce cigs/vis to
MVFR/IFR levels and contain gusty, erratic wind.

A combination of increasing low level moisture, incoming sfc high
pressure, and clearing skies will create conditions favorable for
fog development early Fri morning. The amount of cloud clearing and
influx of moisture from afternoon storms will greatly dictate the
degree of vsby restrictions that will occur. Highest probability for
fog will be within river valleys given its proximity to a moisture
source.

.Outlook...
Generally brief restrictions will be possible Friday and the weekend
in any showers or thunderstorms.

&&

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

&&

Hazardous Weather Outlook
National Weather Service Pittsburgh PA
337 AM EDT Thu Jun 27 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>514-280745-
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-
337 AM EDT Thu Jun 27 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...Today and tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Friday through Wednesday.

The probability for widespread hazardous weather is low.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

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