Severe Thunderstorm Warning 168, NWS Pittsburgh, PA

Area Forecast Discussion
National Weather Service Pittsburgh PA
212 PM EDT Mon Sep 3 2018

.SYNOPSIS...
Heat, humidity and isolated afternoon thunderstorms are
expected through mid-week. A late week cold front will bring
better rain chance and more seasonable temperatures.
Temperatures will be ten degrees cooler next weekend.

&&

.NEAR TERM /THROUGH TUESDAY/...
Scattered showers and storms have developed on the lake breeze
downwind of Lake Erie. This will transition through the forecast
area through the afternoon hours across the northwestern 1/3rd
of the forecast area. Farther southwest in eastern Ohio,
northern West Virginia, and southwestern Pennsylvania, enough
subsidence should offset scattered storm development. HRRR
wants to place isolated storms in this region, but several other
of the CAMS do not. Elected to keep an optimistic dry forecast
rolling, even though most would like the rainfall for their
lawn. Can't rule out a pop up storm, but if any develop they
will be brief and not last long given them will quickly rain
themselves out.

Valley fog will develop overnight, most likely in the Allegheny
river region given they will experience measurable rainfall
during the day. Also the deeper gorges of West Virginia.
Overnight lows will remain humid as dewpoints reside in the
upper 60s to lower 70s.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/...
Heat remains the main story for the short term with Wednesday
being the hottest day of the week. Heat index values will push
into the upper 90s outside of the mountains, but dewpoints will
be in the 69-71F range which will be two degrees short of us
reaching heat advisory criteria /100-100F threshold needed/.

As the mid atlantic ridge weakens mid level heights fall
allowing a weak baroclinic zone to drop south. As it moves
through the forecast area during the afternoon Thursday ramped
up pops to likely as their will be plenty of moisture to tap
even through the trigger mechanism is fairly weak. It is
possible the boundary could cross northern areas precip free
since it will be moving through during the early morning hours.

As this point, do not see a high water nor severe threat. Wind
flow is not that strong. There should be enough movement in the
storms despite PWATS around 1.7 inches that negate a flash flood
threat. If I had to pick which is a greater concern at this
juncture it would be flash flooding.

The only location that could set a record high Tuesday and
Wednesday would be Dubois as benchmarks reside at 88. All of the
longer period of record sites, daily maximums sit in the low
100s.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Highlights:
- Heat Wave is over
- Return to Active Pattern
- Temperatures just above near normal

Overall good agreement amongst long range ensembles for the
extended. By this weekend, there are differences where the cold
front stalls/ washes out over northern West Virginia which will
have affects on pop grids. The next weather system crosses
Sunday. This will bring showers and storms over much of the
region as the low tracks across Lake Erie. GFS is much faster
getting the system through by as much as 12 hours over the
ECMWF.

The good news is the H5 anti-cyclone weakens allowing the
westerlies to setup across the area. This spells a little relief
from the hot weather as daytime highs settle back into the upper
70s to lower 80s save for the mountains. The mean off the
statistical guidance is just below the high end of the
temperature spread, so mid 80s are possible Friday, before a
cool down this weekend.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Lofty high pressure will maintain general VFR and light wind
with caveats for peridawn fog and isolated afternoon convection.
At this point DUJ is the only site with visibility restrictions
in the TAF, but cannot rule out the possibility of vis
restrictions at other terminals.

Outlook...
The next chance for general restrictions will come Thursday with
an encroaching frontal boundary.

&&

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

&&

Hazardous Weather Outlook
National Weather Service Pittsburgh PA
318 AM EDT Mon Sep 3 2018

MDZ001-OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023-
029-031-073>076-WVZ001>004-012-021-509>514-040730-
Garrett-Tuscarawas-Carroll-Columbiana-Coshocton-Harrison-Jefferson-
Muskingum-Guernsey-Belmont-Noble-Monroe-Mercer-Venango-Forest-
Lawrence-Butler-Clarion-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-
318 AM EDT Mon Sep 3 2018

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...Tuesday through Sunday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

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

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