Severe Thunderstorm Warning 284, NWS State College, PA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
249 PM EDT THU SEP 27 2007

.SYNOPSIS...
A COLD FRONT FROM KSYR-KERI-KMFD EARLY THIS AFTN IS PRESSING
SLOWLY SOUTHEAST AND WILL CONTINUE TO MOVE EAST TONIGHT AND FRIDAY
MORNING...AND WILL BE OFF THE EAST COAST BY FRIDAY AFTERNOON. A
LARGE HIGH PRESSURE SYSTEM WILL BUILD INTO PENNSYLVANIA THIS
WEEKEND THROUGH THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 11 PM THIS EVENING/...
AREA OF SHOWERS AND THUNDERSTORMS MOVING INTO WRN PA IS BEING
DRIVEN BY A POTENT SHORTWAVE MOVING EAST FROM THE OHIO VALLEY.
THE MID LEVEL COOLING WITH THIS FEATURE WILL OVERRIDE SOME
ABNORMALLY WARM AND MOIST AIR OVER CENTRAL PA LATE THIS AFTN AND
EVENING. ALMOST FULL SUNSHINE IN THE SE HALF OF THE AREA HAS
ALREADY ALLOWED SOME VERY TALL CU AND A STRAY SHOWER OVER THE
POCONOS AND MID SUSQ VALLEY. EXPECT SHOWERS AND STORMS TO INCREASE
IN COVERAGE FROM W TO SE BEFORE TOO LONG.

SEVERE THUNDERSTORM WATCH 691 IS IN EFFECT UNTIL 10 PM LOCAL TIME.
MAIN THREAT WILL BE WIND WITH MUCH MORE MINOR RISKS FOR HAIL AND
TORS. ANY LINGERING SMALL-SCALE BOUNDARIES FROM OVERNIGHT
CONVECTION COULD ALLOW LLVL HELICITIES TO BE HIGHER IN SPOTS. ONLY
POTENTIALLY SUPPRESSIVE FEATURE IS THE SUBSIDENCE ON THE WRN
PERIPHERY OF THE BAROCLINIC LEAF VISIBLE OFF THE EAST COAST ATTM.
DYNAMICS SHOULD START TO OVERCOME ANY INHIBITION SOON...THOUGH.

WILL RUN WITH HIGH POPS ALL EVENING AND MENTION GUSTY WINDS IN
THUNDERSTORMS FOR MOST OF THE AREA. SOME STORMS COULD BE HEAVY
RAINERS WITH PWATS TOPPING 1.5 INCHES. LARGE AREA OF MODERATE RAIN
WILL MOVE NORTHEAST FROM OHIO INTO OUR NORTHWEST COUNTIES. WILL
MONITOR THIS FOR ANY SMALL STREAM PROBLEMS.

&&

.SHORT TERM /11 PM THIS EVENING THROUGH 6 PM FRIDAY/...
AREA RAINFALL AVERAGES COULD BE ON THE ORDER OF ONE INCH. WE CAN
EASILY HANDLE THAT...BUT IF IT ALL FALLS IN 20 MINUTES...IT COULD
CREATE LOCAL DRAINAGE PROBLEMS. WILL JUST MENTION HEAVY RAIN
POSSIBLE IN STORMS TONIGHT - MAINLY IN THE SOUTH.

AS THE MAIN SHORTWAVE ROLLS EAST AND HEATING DECREASES...WE SHOULD
SEE A DECREASE IN STORMS LATER TONIGHT. FOG MAY AGAIN BECOME
LOCALLY DENSE WITH RAIN AND HIGH MOISTURE.

ANY REMAINING SHWRS SHOULD END OVR EASTERN PA EARLY FRIDAY...AS
THE FRONT SWEEPS EAST OF THE REGION. HOWEVER...DIURNAL HEATING ON
FRIDAY COMBINED WITH COOL POOL MOVING IN ALOFT WILL LIKELY YIELD
SCT AFTN SHWRS...AND PERHAPS THUNDER...MAINLY OVER THE MTNS/UP
NORTH. WILL KEEP CLOSE OR JUST A LITTLE HIGHER THAN ENS MOS GUID
ON TEMPS FOR TONIGHT AND FRI - WITH CLOUDS AND MOISTURE
TONIGHT...AND 8H TEMPS THAT DON/T FALL TOO RAPIDLY UNTIL LATER ON
FRI - WITH 8H TEMPS NEAR +10C OVER KMDT AT 18Z. DOWNSLOPE AND
DRYING WINDS MAY ALSO HELP SE STAY UP A DEG OR TWO FROM GUID.

&&

.LONG TERM /FRIDAY NIGHT THROUGH THURSDAY/...
HIGH PRESSURE AT THE SURFACE AND ALOFT WILL SETTLE OVER THE AREA IN
THE WAKE OF THE CURRENT FRONT. EXCELLENT RADIATIONAL COOLING
ASSISTED BY DEWPOINTS IN THE 30S ON SATURDAY NIGHT WILL ALLOW FOR
LOW TEMPERATURES ABOUT 5-10 DEGREES BELOW NORMAL FOR SUNDAY MORNING.

TEMPERATURES WILL REBOUND INTO EARLY NEXT WEEK AS THE AIRMASS IS
MODIFIED UNDER CLEAR SKIES. PATCHY MORNING FOG WILL RETURN AS
NIGHTS ARE NOW LONGER THAN DAYS.

A DRY SURFACE TROUGH WILL CROSS THE AREA LATE MONDAY OR TUESDAY
ALLOWING FOR A SLIGHT TEMPERING OF HIGHS FOR THE FIRST HALF OF
NEXT WEEK.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
VFR AT MOST SITES...EXCEPT KMDT WITH MVFR HAZE AND KBFD WITH LOW
CLOUDS AND SOME LIGHT FOG. THE STRONG SS SHOULD DESTABILIZE THE
REGION VERY QUICKLY. HAVE STARTED TO THROW IN TEMPOS FOR
-TSRA...AS BIG SHORTWAVE AND UPPER LEVEL FORCING/COOLING MOVE IN
FROM THE WEST. WINDS COULD GUST TO SVR LEVELS IN THE THUNDERSTORMS
THAT FORM.

THE SHRA/TSRA WILL LAST THROUGH MUCH OF THE EVENING AS A COLD FRONT
PRESSES SLOWLY IN FROM THE N/W. MVFR CONDITIONS ARE EXPECTED FOR
MUCH OF THE PERIOD FROM TONIGHT INTO FRIDAY MORNING...WITH AREAS
OF IFR CONDITIONS IN THE HEAVIER SHOWERS AND ISOLATED TSRA.

THE COLD FRONT WILL MOVE TO OUR EAST...BUT SCT SHRA
AND PERHAPS A TSRA WILL BE POSSIBLE IN THE NW MTS /KBFD-KFIG/ FRI
AFTERNOON AS THE COLDEST AIR ALOFT MOVES OVER THE REGION DURING
PEAK HEATING.

VFR CONDITIONS RETURN TO THE REGION LATER ON FRIDAY THROUGH THE
ENTIRE UPCOMING WEEKEND AS A LARGE AREA OF HIGH PRESSURE MOVES
EAST FROM THE CENTRAL U.S...AND THE NW FLOW PRECEDING IT
TRANSPORTS LOW DEWPOINTS IN THE 30S/40S INTO PENN FROM SOUTHERN
CANADA. AREAS OF VALLEY FOG IN THE MORNING MAY BE THE ONLY LIMITING
MVFR/IFR CONDITIONS FOR A FEW HOURS EACH MORNING FRIDAY THROUGH
TUESDAY BETWEEN 09Z-13Z.

&&

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

&&

SYNOPSIS...DANGELO/FITZGERALD
NEAR TERM...DANGELO/TYBURSKI
SHORT TERM...DANGELO
LONG TERM...FITZGERALD/TYBURSKI
AVIATION...DANGELO/STEINBUGL

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE STATE COLLEGE PA
214 PM EDT THU SEP 27 2007

PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-049>053-
056>059-063>066-281815-
WARREN-MCKEAN-POTTER-ELK-CAMERON-NORTHERN CLINTON-CLEARFIELD-
NORTHERN CENTRE-SOUTHERN CENTRE-CAMBRIA-BLAIR-HUNTINGDON-MIFFLIN-
JUNIATA-SOMERSET-BEDFORD-FULTON-FRANKLIN-TIOGA-NORTHERN LYCOMING-
SULLIVAN-SOUTHERN CLINTON-SOUTHERN LYCOMING-UNION-SNYDER-MONTOUR-
NORTHUMBERLAND-COLUMBIA-PERRY-DAUPHIN-SCHUYLKILL-LEBANON-CUMBERLAND-
ADAMS-YORK-LANCASTER-
214 PM EDT THU SEP 27 2007

...SEVERE THUNDERSTORM WATCH 691 IN EFFECT UNTIL 10 PM EDT THIS
EVENING...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

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

   SEVERE THUNDERSTORM WATCH.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

NO HAZARDDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL LIKELY BE NEEDED THIS EVENING.

DANGELO