Flash Flood Warning 3, NWS State College, PA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
136 PM EDT SUN MAY 24 2009

.SYNOPSIS...
A SLOW MOVING COLD FRONT WILL PUSH SOUTHEAST ACROSS NORTH CENTRAL
PENNSYLVANIA THIS AFTERNOON...BECOMING NEARLY STATIONARY SOUTH OF
THE MASON-DIXON LINE LATER TONIGHT INTO MEMORIAL DAY. THE COLD
FRONT SHOULD TRIGGER SCATTERED TO NUMEROUS SHOWERS AND
THUNDERSTORMS THIS AFTERNOON. THE AFOREMENTIONED FRONTAL BOUNDARY
WILL INFLUENCE THE WEATHER FOR MUCH OF THE UPCOMING WEEK AND
PROVIDE A FOCUS FOR OCCASIONAL SHOWERS AND THUNDERSTORMS.

&&

.NEAR TERM /THROUGH TONIGHT/...
ISOLD SHRA/TSRA ARE STARTING TO DEVELOP ACROSS THE NCENT MTNS NEAR
THE SLOW MOVG/DIFFUSE CLD FNT. EXPECT CVRG AND INTENSITY TO
INCREASE THROUGH THE MID-LATE AFTN AHEAD OF THE CLD FRONT...MAINLY
SOUTH AND EAST OF I-80.

EXPECT AFTN HEATING TO ACT ON A RATHER MOIST LOW LEVEL AIRMASS
/BOUNDARY LAYER DEWPOINTS IN THE 60S/ WHICH WILL RESULT IN MODEST
INSTABILITY /ML CAPES 500-1000J/ ALONG AND AHEAD OF THE SLOW-MOVG
FRONTAL ZONE. 00Z SPC 4KM WRF SUPPORTS CONVECTIVE DEVELOPMENT
EITHER SIDE OF 19Z. THE REGION REMAINS ON THE SRN FRINGES OF THE
STRONGEST MID-UPR LVL WLY FLOW ASSOC WITH A NRN STREAM TROUGH
CROSSING QUEBEC/ONTARIO. THIS WILL SUPPORT A UNIDIRECTIONAL DEEP-
LAYER WIND PROFILE...WITH 0-6KM BULK SHEAR VALUES ON THE ORDER OF
20-40KTS. THE BEST SHEAR WILL BE DISPLACED FURTHER NORTH...MAINLY
FROM I-80 NORTHWARD INTO NY STATE. FCST CAPE/SHEAR PARAMETERS WILL
BE SUPPORTIVE OF ORGANIZED TSTORM CLUSTERS. DESPITE FAIRLY STEEP
LOW-LEVEL LAPSE RATES...WEAK FLOW BLW 700MB WILL PRECLUDE A MORE
SUBSTANTIAL SEVERE/DMGG WIND THREAT -- AND MID-LVL LAPSE RATES
NEAR 6C/KM SUGGEST A MARGINALLY FAVORABLE ENVIRONMENT FOR LARGE
HAIL.

WHILE THE OVERALL THINKING IN TERMS OF THE SEVERE THREAT HAS NOT
REALLY CHANGED...HAVE INCREASED POPS INTO THE LKLY CATG FROM STATE
COLLEGE NORTH/EAST BASED ON THE LATEST LOCAL NAM/GFS/SREF ENSEMBLE.
SIMILAR QPF BLEND ALONG WITH HPC PAINTS A MAX OVER THE ECENT
MTNS/MID SUSQ VLY FROM SEG TO AVP.

CONVECTION WILL DIMINISH WITH THE LOSS OF HEATING TONIGHT. A FEW
SHOWERS MAY LINGER EARLY OVER THE SRN TIER...BUT MOST OF THE
REGION SHOULD BE DRY AFT 06Z. DRIER AIR AND MAINLY CLR SKIES WILL
ALLOW TEMPS TO DROP INTO THE 40S ALONG THE PA/NY BORDER.
MEANWHILE...CLOUD COVER AND MILDER AIR WILL PERSIST ACROSS THE
SOUTH WHERE MINS WILL RANGE FROM THE U50S-L60S.

&&

.SHORT TERM /MONDAY/...
Q-STNRY FNTL BNDRY WILL WAVER JUST SOUTH OF THE MASON-DIXON LINE
FOR MEMORIAL DAY. WHILE AN ISOLD AFTN SHRA/TSRA CANNOT BE RULED
OUT ACROSS THE SOUTH WHERE DEWPOINTS WILL REMAIN NEAR 60F...MOST OF
THE AREA WILL REMAIN FAIR/DRY AS SFC HIGH PRES BUILDS SEWD FROM
JAMES BAY INTO NORTHERN NEW ENGLAND.

&&

.LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
UNSETTLED WEATHER MAY TAKE A BRIEF BREAK FOR MEMORIAL DAY...BUT
THE FRONT NEVER GOES FAR AWAY WITH MUCH OF THE UPCOMING WEEK
LOOKING INCREASINGLY HUMID AND UNSETTLED. GEFS/SREF BOTH SHOW A
SURGE IN MOISTURE WITH PWAT ANOMALIES OF 3-4 STD DEV ABOVE NORMAL
RETURNING TO THE REGION BY LATER TUESDAY. WITH THE SFC HIGH
SLIPPING OFF THE COAST...AND MOISTURE FROM THE OLD SEMI- TROPICAL
SYSTEM FEEDING UP THE WEST SIDE OF THE OFFSHORE RIDGE...THE ONLY
QUESTION BECOMES IF WE CAN MANAGE TO DEVELOP A COHERENT TRIGGER TO
PROVIDE A FOCUS FOR SIGNIFICANT RAINS. GEFS SHOWS A HIGH
PROBABILITY OF AT LEAST .50/12HR OF RAIN FROM TUES INTO THURSDAY
WITH A GOOD CHANCE OF AN INCH OR MORE OF RAIN FROM LATER MONDAY
INTO LATE TUESDAY. THE SREF IS LESS CONFIDENT IN THE QPF
PROBABILITIES SHOWING JUST SMALL AREAS OF .50 OR MORE OF RAIN
SCATTERED ABOUT FROM TUES THROUGH THURSDAY.

LOW LEVEL WIND ANOMALIES START OFF WITH EASTERLIES FROM DURING
THE DAY TOMORROW INTO EARLY TUESDAY WHEN THE FLOW SHIFTS MORE TO
THE SSE THEN EVENTUALLY SOUTH. SO WHILE MODELS INITIALLY START OUT
HINTING AT THE POTENTIAL FOR SOME OVERRUNNING PRECIP DEVELOPING
MONDAY NIGHT INTO TUESDAY...THE SCENARIO EVOLVES INTO MORE OF A
SOUTHERLY FLOW/CONVECTIVE THREAT IN TIME. IN FACT...TUESDAY COULD
BE DOWNRIGHT CHILLY WITH OVERRUNNING RAINS AND A STRONG LOW LEVEL
COOL AIR DAMMING SIGNATURE HINTED AT IN ALL THE SHORT RANGE
OPERATIONAL MODELS LI PROGS. THESE MODELS STEADILY ERODE STABILITY
SO THAT BY WEDNESDAY WE ARE IN A HUMID SOUTHERLY FLOW AT ALL
LEVELS. AGAIN...WHETHER WE HAVE A HEAVY RAIN FOCUSING MECHANISM
REMAINS TO BE SEEN...BUT THE GUIDANCE SEEMS TO BE HINTING AT THE
THREAT WITH TROPICAL MOISTURE AND INCREASING INSTABILITY ALL
TAKING AIM AT THE AREA AROUND MID WEEK.

GEFS SHOWS HIGH PRES BUILDING BACK INTO CENTRAL PENN BY THE START
OF THE WEEKEND. THE GEFS MEAN H5 HEIGHTS ALSO SUGGEST INCREASING
AMPLITUDE IN THE LARGE SCALE PATTERN BY WEEKS END...TRANSITIONING
TO AN WCENT NOAM RIDGE/ERN TROF CONFIGURATION.

&&

.AVIATION /17Z SUNDAY THROUGH THURSDAY/...
FOG/HAZE HAS LIFTED ACROSS ALL CENTRAL PENN TERMINALS...AND LOOK
FOR VFR TO BE THE PREVAILING CATG THIS AFTN. HOWEVER...OCNL MVFR
CIGS AND MVFR/IFR VISBYS WILL BE PSBL IN SCT TSTORMS/CB THIS AFTN
INTO THE EVE OVER SCENT AIRFIELDS. AREAS OF MVFR/IFR FOG WILL
LKLY DEVELOP OVERNIGHT ESPECIALLY WHERE IT RAINS.

OUTLOOK...
MON...AM FOG PSBL...THEN VFR.
TUE-THU...OCCASIONAL MVFR IN SHRA/TSRA.

&&

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

&&

SYNOPSIS...STEINBUGL
NEAR TERM...STEINBUGL
SHORT TERM...STEINBUGL
LONG TERM...DANGELO/LACORTE
AVIATION...STEINBUGL

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE STATE COLLEGE PA
739 AM EDT SUN MAY 24 2009

PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-049>053-
056>059-063>066-251145-
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-
739 AM EDT SUN MAY 24 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA.

.DAY ONE...TODAY AND TONIGHT.

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

STEINBUGL

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
245 PM EDT SUN MAY 24 2009

PAZ041-046-241930-
NORTHERN LYCOMING PA-SOUTHERN LYCOMING PA-
245 PM EDT SUN MAY 24 2009

...A STRONG THUNDERSTORM WILL AFFECT EASTERN LYCOMING COUNTY...

AT 243 PM EDT...A STRONG THUNDERSTORM WAS LOCATED NEAR
MONTOURSVILLE...MOVING SOUTHEAST AT 10 MPH.

WIND GUSTS TO 30 MPH AND SMALL HAIL ARE POSSIBLE WITH THIS STORM.
VERY HEAVY RAIN WILL FALL FROM THIS STORM...AND WILL CAUSE WATER TO
POND ON ROADS.

THIS STORM WILL BE NEAR COGAN STATION AROUND 250 PM...LOYALSOCKVILLE
AROUND 310 PM AND MONTOURSVILLE AROUND 330 PM.

THIS WILL IMPACT I-180 BETWEEN MILE MARKERS 14 AND 26.

LAT...LON 4128 7666 4115 7691 4138 7714 4150 7696

EXPERIMENTAL

FORECASTER: STEINBUGL

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
343 PM EDT SUN MAY 24 2009

PAZ045-046-049-051>053-242045-
COLUMBIA PA-MONTOUR PA-NORTHUMBERLAND PA-SOUTHERN CLINTON PA-
SOUTHERN LYCOMING PA-UNION PA-
343 PM EDT SUN MAY 24 2009

...STRONG THUNDERSTORMS WILL AFFECT MONTOUR...NORTHWESTERN
NORTHUMBERLAND...SOUTHEASTERN CLINTON...SOUTHEASTERN LYCOMING...UNION
AND WEST CENTRAL COLUMBIA COUNTIES...

AT 340 PM EDT...STRONG THUNDERSTORMS WERE ALONG A LINE FROM 10 MILES
EAST OF MONTOURSVILLE TO MONTOURSVILLE TO JERSEY SHORE...MOVING
SOUTHEAST AT 15 MPH.

HEAVY DOWNPOURS...WIND GUSTS TO 40 MPH AND HAIL UP TO DIME SIZE ARE
POSSIBLE WITH THESE STORMS.

THESE STORMS WILL BE NEAR LAIRDSVILLE...AND COLLOMSVILLE AROUND 350
PM...MONTGOMERY AROUND 400 PM...ELIMSPORT AROUND 405 PM...DELAWARE
RUN...AND CARROLL AROUND 410 PM...EXCHANGE AROUND 415 PM...
TURBOTVILLE AND ALLENWOOD AROUND 425 PM.

THIS WILL IMPACT THE FOLLOWING CENTRAL PENNSYLVANIA INTERSTATES...
I-80 BETWEEN MILE MARKERS 188 AND 234...I-180 BETWEEN MILE MARKERS 1
AND 29.

THIS WILL ALSO IMPACT THE FOLLOWING MAJOR ROADS...STATE HIGHWAY
147...ROUTE 11...ROUTE 15...ROUTE 220...STATE ROAD 45...STATE ROAD
118.

LAT...LON 4096 7638 4094 7667 4086 7711 4099 7721
      4103 7716 4102 7723 4120 7737 4125 7727
      4130 7695 4127 7665

EXPERIMENTAL

FORECASTER: DEVOIR