Flash Flood Warning 17, NWS State College, PA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
739 AM EDT WED JUL 14 2010

.SYNOPSIS...
A POTENT UPPER LEVEL TROUGH WILL LIFT SLOWLY NORTHEAST FROM THE
CENTRAL APPALACHIANS TO THE MID-ATLANTIC COAST TODAY...AND
EVENTUALLY PUSH OFFSHORE TONIGHT. HIGH PRESSURE WILL MOVE INTO THE
AREA FROM THE GREAT LAKES TONIGHT THROUGH THURSDAY. A COLD FRONT
WILL MOVE INTO THE STATE ON FRIDAY.

&&

.NEAR TERM /UNTIL NOON TODAY/...
WV LOOP SHOWS COMMA HEAD UPPER LOW CENTERED NEAR THE WV PNHNDL
EARLY THIS MORNING...WITH A WELL-DEFINED BAROCLINIC/DEFORMATION
PRECIP SHIELD ORIENTED SW-NE OVR CENTRAL PA. STLT ANALYSIS AND RDR
TRENDS INDICATE AXIS OF HEAVIEST PRECIPITATION WILL BE MAINTAINED
FROM THE POCONOS SWWD BACK THRU THE EAST-CENTRAL MTNS AND MID SUSQ
VLY. DESPITE AMPLE DEEP LYR MOISTURE /STLT DERIVED BLENDED TPW
OVER 200 PCT ABOVE NORMAL/ RAINFALL RATES HAVE BEEN DECREASING
WITH MAXIMUM 0.5"/HOUR OBSERVED NOW IN ONLY A FEW LOCATIONS. 1-6
HR RAINFALL TOTALS HAVE GENERALLY BEEN BELOW FFG...HOWEVER SOME
MINOR FLOODING HAS BEEN OBSERVED. OVERALL...FEEL THAT THE FLASH
FLOOD THREAT IS BECOMING LESS OF AN ISSUE WITH MORE OF A STEADY
STRATIFORM RAIN UNFOLDING OVER THE AREA (AS OPPOSED TO PREVIOUS
CONVECTIVELY-ENHANCED RAINS).

AREAS OF SHALLOW FOG AND STRATUS WILL PLAGUE THE ALLEGHENIES...AS
RESIDUAL POST-FNTL MOISTURE ASCENDS THE HIGHER TERRAIN. THE LOW
CLOUDS AND FOG WILL BURN OFF THRU MID-MORNING. FORECAST
CHALLENGE THROUGH THE NEAR TERM WILL BE IN THE EVOLUTION OF THE
PRECIP SHIELD. ALL GUIDANCE SUGGESTS A SLOW EWD PROGRESSION TO THE
SYSTEM...WITH STEADY DEFORMATION RNFL LKLY CONTINUING THE LONGEST
WITHIN A 60 MILE SWATH CENTERED ALONG A LEWISTOWN LAPORTE LINE.

&&

.SHORT TERM /NOON TODAY THROUGH 6 AM THURSDAY/...
DRIER AIR WILL GRADUALLY WORK INTO THE REGION FROM THE NORTHWEST
LATER TODAY...WITH IMPROVING CONDS ANTICIPATED FROM WEST TO EAST.
KEPT HIGHEST POPS IN THE EAST FOR THE AFTN...AS THE MID-UPPER
TROUGH LIFTS NEWD TOWARD THE MID-ATLC COAST. AN ACCOMPANY SFC COLD
FRONT WILL SHIFT WINDS TO THE NNW WITH CONTINUED CLEARING INTO
TONIGHT.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
UPPER RIDGING WILL BUILD INTO THE REGION FOR THE BEGINNING OF THE
PD WITH CONTINUED WARM AND HUMID WEATHER BUT A DECREASE IN THE
COVERAGE OF DAILY SHOWERS AND THUNDERSTORMS THROUGH THURSDAY.
NORTHERN STREAM ENERGY WILL BRING A COLD FRONT ACROSS THE STATE
LATER FRIDAY AND FRI NIGHT WITH SCATTERED SHOWERS AND
TSRA...FOLLOWED BY AT LEAST A BRIEF BREAK TO THE HEAT AND
HUMIDITY.

GUIDANCE SUGGESTS THAT THE FRONT WILL STALL JUST TO THE SOUTH OF
PA OVER THE WEEKEND AND...COMBINED WITH A RESURGENCE OF MOISTURE
IN RETURN FLOW AND SEVERAL WEAK UPPER DISTURBANCES...WILL LEAD TO
AN INCREASE IN DIURNALLY FORCED CONVECTION FOR SATURDAY AND
SUNDAY. A SECOND COLD FRONT IS FORECAST TO MOVE ACROSS THE STATE
MONDAY AND TUESDAY. THE GFS AND ECMWF BOTH DEVELOP A MODERATE
NORTHWEST FLOW WITH THE PASSAGE OF THE MEAN 5H TROF/COLD FRONT
LATER TUESDAY...AS THE UPPER RIDGE AMPLIFIES OUT WEST. THIS WOULD
SUGGEST SEASONABLY WARM CONDITIONS WITH BELOW NORMAL HUMIDITY
ACROSS THE REGION FOR THE EARLY TO MIDDLE PORTION OF NEXT WEEK.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
BACK EDGE OF PRECIP SHIELD S/E OF JST-UNV-AOO AS UPPER LEVEL
DISTURBANCE AND SFC COLD FRONT CONTINUE TO PUSH EWD THRU CENTRAL
PA. EXPECT RAIN/SHOWERS TO LINGER OVR ERN SXNS BEFORE SLOWLY
TAPERING OFF LATER THIS AFTN. HIGH PRESSURE WILL MOVE INTO THE
AREA TONIGHT BRINGING CLEARING AND VFR FOR THE OVERNIGHT PD. SOME
PATCHY FOG IS POSSIBLE. POOR FLYING CONDS /IFR-MVFR/ WILL PERSIST
THROUGH 12-15Z WITH IMPROVEMENT TO VFR ANTICIPATED BY THIS AFTN.

OUTLOOK...
THU...VFR.
FRI...VFR WITH MVFR POSS IN SHRA/TSRA LATE.
SAT-SUN...VFR...WITH ISOLATED MVFR IN SHRA/TSRA.

&&

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

&&

SYNOPSIS...STEINBUGL
NEAR TERM...STEINBUGL
SHORT TERM...STEINBUGL
LONG TERM...DEVOIR/GARTNER
AVIATION...STEINBUGL

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE STATE COLLEGE PA
452 AM EDT WED JUL 14 2010

PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-049>053-
056>059-063>066-150900-
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-
452 AM EDT WED JUL 14 2010

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA.

.DAY ONE...TODAY AND TONIGHT.

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY.

A COLD FRONT WILL PUSH SOUTHEAST ACROSS PENNSYLVANIA LATER FRIDAY
INTO SATURDAY...ACCOMPANIED BY SCATTERED STRONG TO POSSIBLY SEVERE
THUNDERSTORMS.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.