Severe Thunderstorm Warning 173, NWS Pittsburgh, PA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
641 PM EDT FRI JUL 22 2011

.SYNOPSIS...
A THUNDERSTORM COMPLEX, MOVING EASTWARD THROUGH THE UPPER OHIO
VALLEY CAN CAUSE DAMAGING WIND, HAIL, AND LOCALLY HEAVY RAIN.
STAGNANT HIGH PRESSURE WILL MAINTAIN MUGGY CONDITIONS THIS
WEEKEND, WITH ADDITIONAL THUNDERSTORMS POSSIBLE. A COLD FRONT
WILL BRING SOME RELIEF FROM THE HUMIDITY BY TUESDAY.

&&

.NEAR TERM /THROUGH SATURDAY/...
HAVING COLLABORATED WITH SPC, HAVE ISSUED SEVERE THUNDERSTORM
WATCH FOR THE ENTIRE UPPER OHIO VALLEY. CONTINUE TO HAVE CONCERNS
WITH LOCALLY HEAVY RAIN. AMOUNTS OVER 2 INCHES IN LESS THAN 3
HOURS MAY CAUSE FLOODING. THUNDERSTORM RAINS CAN CAUSE LATE NIGHT HAZE
AND FOG IN THE HUMID SURFACE LAYER OVER NOW WET GROUNDS.

DUE TO MORE CLOUDS AND CHANCES OF THUNDERSTORMS WITH COLD FRONT
APPROACHING, EXPECT HIGH TEMPERATURES SATURDAY TO NOT BE SO HOT AS
PREVIOUS DAYS...ALTHOUGH DEW POINT VALUES WILL REMAIN RELATIVELY
UNCHANGED.

WITH ONLY A FEW EASTERN OHIO COUNTIES EXPECTED TO APPROACH HEAT
ADVISORY CRITERIA TOMORROW AFTERNOON...WILL HOLD OFF ON ANY
HEADLINES AT THIS POINT...ESPECIALLY TO PREVENT CONFUSION WITH
HEADLINES ALREADY IN EFFECT.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH MONDAY/...
WITH COLD FRONT EXTENDING ACROSS THE EASTERN GREAT LAKES SLOWLY
DROPPING TO THE SOUTHEAST...SCATTERED THUNDERSTORMS WILL REMAIN IN
THE FORECAST THROUGH MONDAY. HIGH TEMPERATURES WILL DROP 2-3 DEGREES
EACH DAY DUE TO INCREASING CLOUD COVER WITH THE COLD FRONT...AND AT
THIS POINT...HEAT ADVISORIES ARE NOT ANTICIPATED FOR THESE DAYS.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
CONCUR WITH RECENT HPC GUIDANCE, BASED ON BLEND OF ECMWF AND GEFS
MEAN MODEL OUTPUT, THAT HIGH PRESSURE, COMING EAST FROM THE PLAINS
STATES, WILL INITIALLY PROVIDE LOWER HUMIDITY, LOWER SURFACE DEW
POINTS, ACROSS THE UPPER OHIO VALLEY TUESDAY AND WEDNESDAY. HIGH
TEMPERATURES WILL ALSO BE SLIGHTLY LOWER THAN ON PREVIOUS DAYS, BUT
STILL A COUPLE DEGREES WARMER THAN NORMAL, JUDGING FROM GFS MOS.

AS HIGH PRESSURE PASSES EAST TO THE ATLANTIC COAST, LOW LEVEL
SOUTHWEST WINDS WILL RETURN HOTTER TEMPERATURES AND MORE HUMID
CONDITIONS, HIGHER DEW POINTS, THURSDAY AND FRIDAY, AS INDICATED BY
GFS MOS AND ECMWF MODEL OUTPUT. THIS SHOULD INTRODUCE AT LEAST A
SLIGHT CHANCE OF THUNDERSTORMS, BUT NOT WORTH THE MENTION AT THIS
JUNCTURE.

&&

.AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
BASED ON RECENT RADAR DATA, EXPECT THUNDERSTORM COMPLEXES WITH
POTENTIAL IFR RESTRICTIONS IN HEAVY RAIN AND WIND GUSTS 35-50 KTS.
HAIL ALSO POSSIBLE. THUNDERSTORM COVERAGE WILL LOWER TO ISOLATED
LATE TONIGHT. HOWEVER EXPECT MVFR HAZE AND PATCHES OF IFR FOG
THROUGH 14Z.

THE REST OF DAYTIME SATURDAY, EXPECT LATE MORNING VISIBILITIES TO
IMPROVE TO VFR WITH CUMULUS DEVELOPMENT THROUGH THE AFTERNOON.
A NEARBY FRONT CAN INITIATE BANDS OF SCATTERED THUNDERSTORMS, WITH
POSSIBLE RESTRICTIONS, IN THE HUMID, UNSTABLE AIR MASS INTO
SATURDAY EVENING.

OUTLOOK /SATURDAY NIGHT THROUGH WEDNESDAY/...
EXPECT LATE NIGHT AND EARLY MORNING MVFR HAZE AND IFR FOG ALONG
WITH SCATTERED MAINLY AFTERNOON AND EVENING THUNDERSTORMS THROUGH
MONDAY. EXPECT PREVALENT VFR TUESDAY AND WEDNESDAY.

&&

.CLIMATE...
DAILY RECORD HIGH TEMPERATURES

JULY 22...
PITTSBURGH 96 AT 157 PM TIED RECORD FROM 1933.
PEAK HEAT INDEX 104.
LAST TIME TEMPERATURE AS HOT AS 96 WAS ON AUGUST 15TH 1995.
LAST TIME HOTTER THAN 96 WAS 100 ON JULY 15TH 1995.

PITTSBURGH WARMEST LOW THIS DATE 75 FROM 1978. AS OF 7PM...THE LOW
TEMPERATURE HAS BEEN 75...BUT THE TEMPERATURE MAY DROP BELOW 79 BY
THE END OF THE DAY.

ZANESVILLE OH TIED RECORD OF 96 FROM 1991.

MORGANTOWN WV 96 BROKE RECORD 95 FROM 1957.

JULY 23...
PITTSBURGH PA 98 FROM 1933.
ZANESVILLE OH 96 FROM 1991.
MORGANTOWN WV 95 FROM 1991.

LENGTH OF CLIMATE RECORDS...
PITTSBURGH PA RECORDS BEGAN 1871, AT PIT INTL AIRPORT SINCE 1952.
ZANESVILLE OH RECORDS BEGAN 1946.
MORGANTOWN WV RECORDS BEGAN 1948.

&&

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

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE PITTSBURGH PA
549 PM EDT FRI JUL 22 2011

MDZ001-OHZ039>041-048>050-057>059-068-069-PAZ007>009-013>016-020>023-
029-031-073>076-WVZ001>004-012-021>023-041-232200-
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-
549 PM EDT FRI JUL 22 2011

...SEVERE THUNDERSTORM WATCH 672 IN EFFECT UNTIL 1 AM EDT SATURDAY...

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...TONIGHT.

PLEASE LISTEN TO NOAA WEATHER RADIO OR GO TO WEATHER.GOV ON THE
INTERNET FOR MORE INFORMATION ABOUT THE FOLLOWING HAZARDS.

   SEVERE THUNDERSTORM WATCH.

THUNDERSTORM RAINFALLS OVER 2 INCHES MAY CAUSE LOCALLY RAPID
FLOODING.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

APPARENT TEMPERATURES SATURDAY CAN PEAK IN THE RANGE OF 95 TO 100.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

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