Special Weather Statement, NWS Pittsburgh, PA

Area Forecast Discussion
National Weather Service Pittsburgh PA
1239 PM EDT Thu Oct 21 2021

.SYNOPSIS...
Showers and thunderstorms return this afternoon and evening with a
cold front. Winds will be gusty, with an isolated strong to severe
storm possible.

&&

.NEAR TERM /THROUGH TONIGHT/...
Sfc and coupled upper low pressure will sweep across the Great Lakes
toward northern New England through tonight, with the associated cold
front moving through the Upper Ohio River Valley this afternoon and
evening. A strengthening upper jet as the upper low pivots from a
positive to neutral tilt will further support the front in
developing showers and thunderstorms. Showers will quickly diminish
this evening with FROPA due to dry advection and increasing
subsidence.

An isolated strong to severe thunderstorm capable of producing
damaging wind will be possible along the broken line of storms ahead
of the front. This will be supported by strong shear and strong
winds aloft, but weak instability due to lack of strong
heating/deeper moisture should limit a more widespread wind threat.

As a longwave trough sets up over the Great Lakes tonight into
Friday, an additional shortwave may provide enough vertical motion to
promote localized light rain and/or drizzle early Friday morning
given a moist boundary layer.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
A series of shortwaves with their jet maxima will cross the region
Friday through Saturday as upper trough remains positioned over the
Great Lakes. Periods of mostly isolated showers are possible while
clouds remain fairly abundant. The lack of warming and insolation
plus remnant cold advection will keep area temperature a few degrees
below normal.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
Surface low pressure is expected to deepen and slowly lift from the
Central Plains Sunday in response to a developing trough/jet moving
through the area. The associated warm front will lift northward into
the Ohio River Valley as flow aloft becomes more zonal, with
strengthening jet support and warm/moist advection leading to
increased stratiform rain chances Sunday afternoon into Monday.

The low and upper trough should cross the region Monday into Tuesday,
bringing widespread rain and slightly cooler temperature. Drier and
unseasonably warm should develop thereafter as notable ridging is
expected to build in advance of the next low pressure system.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
A surface cold front is expected to cross the region west to east
this afternoon and evening, with a broken line of showers and
thunderstorms along and just ahead of its leading edge. Isolated gust
up to 40kt may be possible with the stronger storms, otherwise expect
a brief gust and slow veering of sfc wind to the W.

Convection will quickly diminish after FROPA due to cold, dry
advection. Additional shortwave pulses from the overhead trough
should encourage MVFR/IFR cig development and even patchy
sprinkles/drizzle. Timing and duration of these impacts are a little
uncertain as upper flow won't be oriented out of the favorable/more
typical NW.

.Outlook...
Periodic restrictions are expected through the weekend due to upper
troughing, with weak pulses creating localized brief rain chances.
More widespread restrictions and precipitation is likely late Sunday
into early next week with the next low pressure system.

&&

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

&&

Hazardous Weather Outlook
National Weather Service Pittsburgh PA
241 AM EDT Thu Oct 21 2021

OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023-029-
031-073>076-WVZ001>004-012-021-509>514-220645-
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-
241 AM EDT Thu Oct 21 2021

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

.DAY ONE...Today and tonight.

Isolated strong to damaging wind gusts will be possible in the
strongest storms this afternoon and evening with a crossing cold
front.

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

Hazardous weather is not expected at this time.

.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
128 PM EDT Thu Oct 21 2021

OHZ041-211800-
Columbiana OH-
128 PM EDT Thu Oct 21 2021

...A STRONG THUNDERSTORM WILL IMPACT NORTHWESTERN COLUMBIANA COUNTY
THROUGH 200 PM EDT...

At 128 PM EDT, Doppler radar was tracking a strong thunderstorm over
Alliance, or 13 miles west of Salem, moving northeast at 40 mph.

HAZARD...Wind gusts up to 50 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...
Salem, Columbiana, Leetonia, Homeworth, North Georgetown, and Winona.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4090 8082 4090 8058 4080 8109 4090 8108
      4090 8090 4093 8089 4093 8082
TIME...MOT...LOC 1728Z 240DEG 49KT 4091 8111

MAX HAIL SIZE...0.25 IN
MAX WIND GUST...50 MPH

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Special Weather Statement
National Weather Service Pittsburgh PA
349 PM EDT Thu Oct 21 2021

PAZ007>009-014>016-022-212030-
Armstrong PA-Jefferson PA-Butler PA-Forest PA-Clarion PA-Venango PA-
Mercer PA-
349 PM EDT Thu Oct 21 2021

...A CLUSTER OF STRONG THUNDERSTORMS WILL IMPACT NORTHEASTERN
MERCER...VENANGO... NORTHEASTERN BUTLER...NORTHERN
JEFFERSON...NORTHWESTERN ARMSTRONG... CLARION AND FOREST COUNTIES
THROUGH 430 PM EDT...

At 348 PM EDT, Doppler radar was tracking a strong thunderstorm 14
miles east of Slippery Rock, or 14 miles southwest of Knox, moving
northeast at 55 mph.

HAZARD...Wind gusts of 50 to 55 mph.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Oil City, Franklin, Clarion, Brookville, Marienville, Knox,
Rimersburg, Sugarcreek, Brockway, Tionesta, Hasson Heights, and
Stoneboro.

This includes the following highways...
  Interstate 79 in Pennsylvania between mile markers 128 and 137.
  Interstate 80 in Pennsylvania between mile markers 25 and 81.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If outdoors, consider seeking shelter inside a building.

&&

LAT...LON 4144 7896 4144 7897 4145 7898 4145 7906
      4142 7907 4142 7909 4134 7909 4136 7904
      4135 7902 4138 7897 4127 7876 4088 7986
      4148 8025 4149 8000 4156 7991 4160 7983
      4162 7983 4163 7896
TIME...MOT...LOC 1948Z 242DEG 46KT 4114 7979

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...55 MPH