Hail and Damaging Wind in Pennsylvania, September 9, 2008

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
443 AM EDT TUE SEP 9 2008

.SYNOPSIS...
A COLD FRONT WILL PUSH SOUTHEAST ACROSS PENNSYLVANIA TODAY. HIGH
PRESSURE WILL BUILD OVER THE REGION TONIGHT THROUGH THURSDAY.
A LOW PRESSURE SYSTEM WILL LIKELY PASS JUST SOUTH OF PENNSYLVANIA
FRIDAY OR FRIDAY NIGHT.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
08Z SFC ANALYSIS SHOWS COLD FRONT ENTERING NW PA ATTM. POTENT
SHORTWAVE TRACKING THRU THE GRT LKS WILL PUSH FRONT THRU NW PA
EARLY TDY...THEN EXITING THE LOWER SUSQ VALLEY BY LATE AFTN.

MAIN FCST CONCERN TDY WILL BE POTENTIAL FOR SVR WX OVR THE SUSQ
VALLEY...WHERE SREF PLUME DATA INDICATES MODERATE CAPE DEVELOPING
BY AFTN IN ADVANCE OF APPROACHING FRONT. STRONG MID LEVEL FLOW ON
SOUTHERN PERIPHERY OF SHORTWAVE SHOULD RESULT IN AMPLE SHEAR TO
PRODUCE ORGANIZED /POSS SVR/ CONVECTION ACROSS SOUTHEAST
PA...MAINLY BTWN 17Z-22Z.

ALSO OF CONCERN WILL BE POTENTIAL OF LOCALIZED FLASH FLOODING OVR
THE LOWER SUSQ VALLEY...WHERE 1HR FFG REMAINS LOW /BTWN 1 AND 1.5
INCHES/ DUE TO RECENT RAIN FROM TS HANNA. GIVEN ANOMALOUS
PREFRONTAL PWATS...CAN/T RULE OUT A SPOT OR TWO SURPASSING
FFG...MAINLY OVR ADAMS/YORK/LANCASTER COUNTIES. NOT CONFIDENT
ENOUGH TO ISSUE FFA AT THIS POINT...ESPECIALLY SINCE THE THREAT
WILL LIKELY BE LOCALIZED.

PAINTED PARTIAL CLEARING AND DIMINISHING CHC FOR SHRA/TSRA AFTER
16Z ACROSS THE NW ZONES...AND BY 20Z ACROSS MUCH OF CENTRAL PENN
AS THE DEEPER MOISTURE CONVERGENCE ALONG THE LEE SIDE TROUGH
SHIFTS OVER OR JUST TO THE EAST OF SUSQ RIVERS MAIN STEM.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
HI PRES BUILDS INTO THE REGION TONIGHT AND WEDNESDAY. ACCOMPANYING
DRY AIRMASS AND DIMINISHING WINDS SHOULD ALLOW TEMPS TO GET QUITE
CHILLY OVR THE NORTHERN MTNS TONIGHT...RESULTING IN AREAS OF
VALLEY FOG IN THAT AREA TOWARD DAWN. SREF MEAN 850 TEMPS SUPPORT
HIGHS WITHIN A FEW DEG OF 70F WEDNESDAY UNDER ABUNDANT SUNSHINE.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
ANOTHER COOL NIGHT IN STORE FOR CENTRAL PA WED NITE...AS DRY
AIRMASS /SREF PWATS -1SD TO -SD/ COMBINES WITH CLEAR SKIES LIGHT
WINDS. HAVE INCLUDED PATCHY FOG ARND DAWN TO MOST OF THE
AREA...WHICH COULD BE LOCALLY DENSE NEAR ANY BODIES OF WATER.

FAIR WX AND A DRY BNDRY LYR FOR THUR...LIMITING THE CU FIELD ONCE
AGAIN. MIXED LYR WILL REMAIN SHALLOW THUR AFTN...SO EXPECT TEMPS
TO REMAIN SEASONAL.

FLOW APPEARS TO BECOME FLUID AND PROGRESSIVE AS SFC RIDGE SLIDES
OFFSHORE ALLOWING MOISTURE TO POOL INTO THE MID/UPPER ATMOS FRI/SAT.
ATTM THE CHALLENGE FOR THE UPCOMING WEEKEND IS WHETHER WE WILL SEE A
WEAK MOIST ONSHORE FLOW ALONG SOUTHERN PERIPHERY OF RIDGE. THIS
COULD RESULT IN A DAMP FRI/SAT...AS SEVERAL ENSEMBLE MEMBERS HINT AT
FRONTAL BNDRY HANGING UP ARND MID ATLANTIC REGION. ATTM HAVE SIDED
WITH GEFS IN THERMAL RIDGE POKING NORTH INTO THE MID-ATLANTIC LATE
WEEK...AS T850 IN THE MID TEENS SHUD PUSH MAX T A FEW DEGREES
ABOVE NORMAL AND CHC SHRA/TSRA FOR THE WEEKEND ALONG FRONTAL
BNDRY.

INCREASING CONFIDENCE IN A HIGH AMPLITUDE PAC NW RIDGE...ALLOWING A
DOWNSTREAM TROUGH TO DIG INTO CENTRAL CONUS/GRT LKS SUN. GIVEN
PROGRESSIVE FLOW AND NOT MUCH BLOCKING OFFSHORE OF NEW
ENGLAND...TROUGH SHUD SWING THROUGH PA MON WITH ANOTHER CHC FOR
SHRA/TSRA AND COOLER TEMPS TO START NEXT WEEK.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
LYRD MID AND HIGH CLOUDS WILL OVERSPREAD CENTRAL PENN FROM THE
SOUTHWEST OVERNIGHT. ALSO OVERNIGHT...INCREASING SWRLY WINDS ALOFT WILL LEAD
TO LOW LEVEL WIND SHEAR THOUGH ABOUT 12Z...ESPECIALLY ACROSS THE
NW HALF OF PENNSYLVANIA.

SHOWERS AND THUNDERSTORMS WILL BECOME LIKELY ACROSS THE NW MTNS
OVER THE NEXT SEVERAL HOURS. MOST CIGS AND VSBYS WILL DIP ONLY
INTO THE MVFR CATEGORY AT WORST BETWEEN 04Z AND 12Z TUESDAY.

A COLD FRONT ASSOCD WITH A DVLPG LOW PRES SYS MOVG NEWD FM THE
GRT LKS AND INTO THE ST LAWRENCE VLY IS FCST TO PASS THRU THE AREA
LATER TODAY...BRINGING WITH IT NUMEROUS SHOWERS AND ISOLD TSRA.

MAINLY MVFR CIGS AND VSBYS WILL ACCOMPANY AND PRECEDE THE
FRONT...WITH WITH LOCALIZED IFR CIGS/VSBYS IN THE STRONGER STORMS
(AND ALSO IN THE MOIST WRLY UPSLOPE FLOW AT KJST AND KBFD FOR A
FEW HOURS IMMEDIATELY AFTER THE COLD FRONTAL PASSAGE.

HI PRESSURE IS EXPECTED TO BUILD IN FOR FOR TUESDAY NIGHT THROUGH
THURSDAY EVENING ACCOMPANIED BY GOOD FLYING CONDS...OUTSIDE OF A
FEW HOUR PERIOD OF VALLEY FOG (BOTH WED AND THUR) AND RESTRICTED
EARLY MORNING VSBYS.

DETERIORATING CIGS AND VSBYS WILL OCCUR AGAIN LATER THURSDAY NIGHT
AND FRIDAY WITH SCATTERED SHOWERS.

&&

.CTP WATCHES/WARNINGS/ADVISORIES...
NONE.

&&

SYNOPSIS...FITZGERALD
NEAR TERM...FITZGERALD
SHORT TERM...FITZGERALD
LONG TERM...FITZGERALD/BEACHLER
AVIATION...GARTNER/STEINBUGL

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
427 AM EDT TUE SEP 9 2008

PAZ024-025-090900-
BLAIR PA-CAMBRIA PA-
427 AM EDT TUE SEP 9 2008

...A STRONG THUNDERSTORM WILL AFFECT CAMBRIA AND WEST CENTRAL BLAIR
COUNTIES...

AT 421 AM EDT...A STRONG THUNDERSTORM WAS LOCATED NEAR WESTMONT...
MOVING NORTHEAST AT 45 MPH.

WIND GUSTS TO 40 MPH AND SMALL HAIL ARE POSSIBLE WITH THIS STORM.

THIS STORM WILL BE NEAR NANTY-GLO AROUND 440 AM...EBENSBURG AROUND
450 AM AND ASHVILLE AROUND 500 AM.

FORECASTER: KF

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
439 AM EDT TUE SEP 9 2008

PAZ019-025>027-090915-
BLAIR PA-HUNTINGDON PA-MIFFLIN PA-SOUTHERN CENTRE PA-
439 AM EDT TUE SEP 9 2008

...STRONG THUNDERSTORMS WILL AFFECT NORTHEASTERN MIFFLIN...NORTHERN
BLAIR...NORTHERN HUNTINGDON AND SOUTH CENTRAL CENTRE COUNTIES...

AT 434 AM EDT...STRONG THUNDERSTORMS WERE ALONG A LINE FROM
HUNTINGDON TO ALTOONA...MOVING NORTHEAST AT 47 MPH.

WIND GUSTS TO 40 MPH AND SMALL HAIL ARE POSSIBLE WITH THESE STORMS.

THESE STORMS WILL BE NEAR MCALEVYS FORT AROUND 450 AM...SEVEN
MOUNTAINS AROUND 500 AM AND PARK FOREST AROUND 510 AM.

FORECASTER: KF