Damaging Wind in Pennsylvania, September 3, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
200 PM EDT TUE SEP 3 2002

...SEVERE THUNDERSTORM WATCH THIS AFTERNOON IN NORTHWEST....

A SURGE OF MODERATE INSTABILITY...SLIGHTLY ABOVE NORMAL PWAT AND
SOME 1-1.5SD 850 WINDS POSE THE RISK OF SOME THUNDERSTORMS AHEAD OF
THE APPROACHING COLD FRONT TO REACH SEVERE LIMITS. THE BEST THREAT
MAY STAY TO OUR NORTH. THE MODELS SHOW THIS FRONT WEAKENING AND NOT
PUSHING TOO FAR TO OUR SOUTH.  RAINFALL IN SOUTHERN AND EASTERN
SECTIONS COULD BE NON-EXISTENT.  KEPT BEST POPS IN WEST/NORTHWEST
WHERE THE LAKE BREEZE COMBINED WITH THE FRONT MAY INITIATE SOME CONVECTION.

AS FOR THE FRONT...LOW LEVEL THICKNESS ANOMALIES SHOW SOME
ANOMALOUSLY WARM AIR JUST TO OUR SOUTH ON WEDNESDAY OVER NC AND
SOUTHERN VA.  HOWEVER...ANOMALOUS NORTHWESTERLY FLOW AT 850 HPA AND
-1 TO -1.5 SD PWATS FORECAST ON WED SUGGEST COOLER AND MORE
COMFORTABLE WEATHER OVER CENTRAL PA WED. SHOULD BE MOSTLY SUNNY TOO.
HIGH PRESSURE AND THE LOW PWAT VALUES SUGGEST COOL THURSDAY AM AND
AGAIN FRIDAY AM.  WITH LIGHT WINDS WE ARE SETTING UP FOR EXCELLENT
VALLEY/RADIATIONAL FOG CONDITIONS LATER THIS WEEK.

THERMAL AND HEIGHT FIELDS ARE CLOSE TO NORMAL WED-THU. NOT
SURPRISING...GUIDANCE IS DRY AND HAS TEMPS WITHIN 1-2 DEGREES OF
EACH OTHER.

...EXTENDED...

THE ONLY HINT OF A SLIGHTLY BELOW NORMAL DAY FOR HIGHS AND LOWS IS
FRIDAY.  IN FORECAST...SHOWED FRIDAY AS THE COOLEST DAY OF THE WEEK.
HOWEVER MODELS SHOW ANTICYCLONIC CONDITIONS WILL DOMINATE THE REGION
THROUGH EARLY NEXT WEEK...SO DESPITE INCREASING ABOVE NORMAL
THICKNESS...850 HPA TEMPS...AND HEIGHTS SAT-TUESDAY...MORNING LOWS
SHOULD LINGER CLOSE TO NORMAL VALUES.(MDT 59 AND IPT 56 FOR THIS
PERIOD).  DAYTIME HIGHS SAT-TUES SHOULD RUN ABOVE SEASONAL NORMALS
(MDT: 79 IPT: 76 AND BFD: 70).  ENSEMBLE MOS IS GENERALLY RUNNING
3-5F ABOVE THIS MOST OF THE FORECAST PERIOD.  IT LOOKS DRY TOO.

BASED ON RADIATIONAL COOLING CONSIDERATIONS AND THE FACT THAT WE ARE
NOW ROLLING INTO PEAK RADIATIONAL FOG SEASON...WILL SEE IF SOFTWARE
WILL ALLOW THE WEATHER TO SHOW PATCHY MORNING FOG FRI-MONDAY.  THE
WARM STREAM VALLEYS COMBINED WITH A SURFACE ANTICYCLONE SHOULD BE
IDEALLY SUITED FOR THIS SCENARIO.

THE ENSEMBLES SHOW GOOD AGREEMENT IN FORECAST OVER ALL WITH BELOW
NORMAL HEIGHTS IN WEST.  THIS PATTERN SUGGESTS WE SHOULD BE SLIGHTLY
ABOVE NORMAL AS FORECAST BY MREF MOS.  LOW-LEVEL ANTICYCLONIC
CONDITIONS WITH COOL MORNING LOWS MAY MITIGATE THIS TO SOME
DEGREE.

.CTP...
PA...SEVERE THUNDERSTORM WATCH TIL 6 PM NORTHWESTERN COUNTIES.

GRUMM

PAZ004>006-010-011-032200-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1222 PM EDT TUE SEP 3 2002

...A SEVERE THUNDERSTORM WATCH IS IN EFFECT UNTIL 600 PM EDT TUESDAY
EVENING FOR THE FOLLOWING COUNTIES IN CENTRAL PENNSYLVANIA...

MCKEAN...WARREN...CAMERON...POTTER AND ELK.

SCATTERED SHOWERS AND THUNDERSTORMS WILL DEVELOP OVER LAKE ERIE AND
MOVE ACROSS THE WATCH AREA THIS AFTERNOON...AHEAD OF AN ADVANCING
COLD FRONT.  SOME STORMS MAY CONTAIN POTENTIALLY DAMAGING WIND GUSTS
AND LARGE HAIL.

STAY TUNED TO NOAA WEATHER RADIO AND OTHER LOCAL MEDIA FOR FURTHER
DETAILS OR UPDATES.

DEVOIR