Severe Thunderstorm Warning 232, NWS Pittsburgh, PA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
936 AM EDT THU SEP 12 2013

.SYNOPSIS...
A STRONG COLD FRONT WILL SWEEP WARMTH AND HUMIDITY FROM THE UPPER
OHIO VALLEY REGION TODAY AND PROVIDE MORE SHOWERS AND STORMS. MUCH
COOLER WEATHER IS IN STORE FRIDAY AND SATURDAY BEFORE TEMPERATURES
REBOUND TO NORMAL LEVELS.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
UPDATED FORECAST TO ACCOUNT FOR LATEST TIMING ON PCPN ASSOCIATED
WITH THE FIRST COLD FRONT. LATEST DAY1 CONVECTIVE OUTLOOK BROUGHT
SLIGHT RISK FARTHER SW INTO NWRN WV. WITH THE AMOUNT OF STRATUS
IN A RICH ATMS...DUE NOT FORESEE WIDESPREAD SVR WX. ISOLD SVR WX
APPEARS TO BE A STRETCH TOO GIVEN HOW WEAK EFFECTIVE SHEAR IS
PROGGED. MEAN CLOUD LAYER IS 20KTS ALLOWING STORMS TO MOVE AT A
GOOD CLIP SO ANY FLOODING WILL BE LOCALIZED...BUT PROB IN THAT IS
LOW AS WELL. PREVIOUS DISCUSSION FOLLOWS:

TWO FRONTS TO KEEP AN EYE ON TODAY. THE FIRST WILL MOVE THROUGH
THIS MORNING AND THE SECOND LATE THIS AFTERNOON. ACTIVITY WILL
DEVELOP BETWEEN THE BOUNDARIES AND MOVE EASTWARD AS THE DAY
PROGRESSES. ACTIVITY TO THE WEST IS STRETCHING OUT ON THE NORTHERN
SIDE OF FRONT #1. THE ACTIVITY SHOULD BLOSSOM AFTER SUNRISE AND
BEGIN TO OVERSPREAD THE NORTH BETWEEN 14 AND 16Z. SHOWERS AND
STORMS WILL DRIFT SOUTHWARD THROUGH THE AFTERNOON.

STILL HAVE QUESTIONS ON STRENGTH OF THE ACTIVITY. ATMOSPHERE WILL
BE PLENTY UNSTABLE...PARTICULARLY ACROSS THE SOUTH WITH HIGH CAPES
AND LOW LI'S. FORECAST SOUNDINGS ARE NOT OVERLY IMPRESSIVE WITH
K-INDEX VALUES IN THE LOW 30S AND MDPI/WINDEX AROUND .50/30-35.
TIMING WILL HINDER DEVELOPMENT AS INITIALLY CONVECTIVE TEMPS ARE
IN THE LOWER TO MID 80S. CONVECTIVE TEMPS DO COME DOWN TO
REASONABLE VALUES BY LATE MORNING...BUT BY THEN THERE WILL ALREADY
BE ACTIVITY ON GOING AND PLENTY OF CLOUD COVER. AT THIS
TIME...THINK THE BEST WAY TO HANDLE WILL BE CAT SHOWER/CHC STORMS.

THE VERY UNSTABLE AIR WILL BE FORCED SOUTHWARD WITH THE FIRST
FRONT DURING THE AFTERNOON. BECAUSE OF THIS WOULD THINK THAT THE
BEST AREA FOR STRONG/SEVERE ACTIVITY WOULD BE ACROSS THE SOUTHERN
HALF OF THE AREA IN THE LATE MORNING/AFTERNOON. ALSO HAVE A
FEELING THAT HEAVY RAIN COULD BE A GREATER THREAT AS MOISTURE
CONVERGENCE INCREASES IN THE SOUTH AND PWATS JUMP UP TO AROUND 1.8
INCHES. SPC HAS KEPT THE AREA IN A GENERAL THUNDERSTORM...KEEPING
THE SLIGHT RISK AREA TO OUR EAST.

CLOUD COVER WILL BE IMPORTANT ONCE AGAIN. SOME DRIER AIR HAS
SETTLED IN OVER THE OHIO VALLEY WHICH COULD ALLOW FOR SUNSHINE IN
THE MORNING. WILL NEED TO KEEP CLOSE WATCH ON AMOUNT OF SUN BEFORE
THE ACTIVITY REACHES THE AREA.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
FRONT WILL CLEAR THE AREA BY 00Z...WITH SOME LINGERING SHOWERS
POSSIBLE ACROSS THE SOUTHEAST. DRY AIR WILL MOVE SOUTHWARD IN THE
NW FLOW. MAIN TROUGH SWINGS THROUGH LATE TONIGHT WITH STRONG CAA.
STRATOCU IS LIKELY TO COVER THE AREA LATE TONIGHT WITH THE COLDER
AIR.

TROUGH WILL REMAIN OVER THE REGION THROUGH MUCH OF FRIDAY WITH
ANOTHER STRONG UPPER LEVEL WAVE MOVING SOUTHWARD ON THE WESTERN
EDGE. WITH NW FLOW ACROSS THE LAKES...AND CAA CONTINUING...
ISO/SCT SHOWERS COULD DEVELOP FRIDAY. BEST AREA FOR SHOWER
DEVELOPMENT WOULD BE ACROSS THE NORTHERN HALF.

TROUGH WILL SWING EASTWARD FRIDAY NIGHT PULLING THE COLDEST AIR
OVER THE UPPER OHIO VALLEY. EXPECT CLOUDS TO HOLD ON MOST OF
FRIDAY NIGHT...WITH WELL BELOW NORMAL TEMPS.

RISING HEIGHTS AND SURFACE HIGH WILL ALLOW FOR A COOL AND
COMFORTABLE SAT. HAVE LOWERED HIGHS ON SAT IN ACCORDANCE WITH
LATEST MODEL DATA SHOWING 85H TEMPS AROUND +4. FORECAST SHOWING A
MIXING LAYER UP TO AROUND 4000FT WHICH SHOULD ALLOW THE COLDER AIR
TO MIX DOWN. DID NOT WANT TO GO TO LOW...AS STILL DEALING WITH AN
EARLY SEPTEMBER SUN.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
THE POSITION OF HIGH PRESSURE COME DAWN SUN MRNG WILL NOT BE
IDEAL FOR RADIATIONAL COOLING...BUT IT WILL BE A CHILLY NIGHT. 40S
WILL BE COMMON FOR MINIMUM TEMPS WITH UPR 30S ACR DEEPER MTN
VALLEYS AND N OF I-80. RETURN FLOW USHERS IN WARMER WEATHER
SUNDAY INTO EARLY NEXT WEEK. THE ONE WEATHER SYSTEM TO SPEAK OF IS
A MOISTURE STARVED COLD FRONT CROSSING SUN NGT INTO MON. ELECTED
TO CONTINUE NO POPS FOR THIS BOUNDARY AS IT TRAVERSES.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
MAINLY MVFR CONDS IN BR/PTCHY STRATOCU WL INCR TO VFR THIS MRNG. A
STG CDFNT WL MOVE ACRS THE RGN THIS AFTN WITH A ROUND OF MVFR SHWRS
AND PSBL TSTMS. INCLUDED VCTS FOR SITES S OF I 80 WHERE THE BEST
INSTBY IS PROGGED...ALTHOUGH STILL MENTIONED MVFR SHWRS N OF I 80.
EXP A WSHFT TO THE NW AFT FROPA. THE FNT SHOULD EXIT THE RGN ERLY
THIS EVE WITH SCT-BKN STRATOCU DVLPG OVRNGT.

.OUTLOOK.../FRIDAY THROUGH MONDAY/...
RSTRNS ARE PSBL FRI IN SCT SHWRS AS AN UPR TROF MOVES ACRS THE
GT LKS...OTRW VFR CONDS EXP THRU THE PD.

&&

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

&&

SYNOPSIS...98
NEAR TERM...98/22
SHORT TERM...22
LONG TERM...07
AVIATION...07

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PITTSBURGH PA
1053 AM EDT THU SEP 12 2013

MDZ001-OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023-
029-031-073>076-WVZ001>004-012-021>023-041-131500-
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-PRESTON-TUCKER-
1053 AM EDT THU SEP 12 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR WESTERN MARYLAND...EAST
CENTRAL OHIO...NORTHWEST PENNSYLVANIA...SOUTHWEST
PENNSYLVANIA...WEST CENTRAL 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.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE PITTSBURGH PA
838 AM EDT THU SEP 12 2013

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0655 PM     TSTM WND DMG     1 ESE BETHLEHEM         40.04N  80.67W
09/11/2013                   OHIO               WV   DEPT OF HIGHWAYS

            TREES DOWN ON EAST COVE AVENUE

0659 PM     TSTM WND DMG     4 ESE WEST LIBERTY      40.16N  80.53W
09/11/2013                   OHIO               WV   DEPT OF HIGHWAYS

            TREES DOWN ON CASTLEMAN RUN ROAD

&&

EVENT NUMBER PBZ1302749
EVENT NUMBER PBZ1302750

98

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