Damaging Wind in Pennsylvania, June 16, 2010

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
803 PM EDT WED JUN 16 2010

.SYNOPSIS...
WARM...MOIST AIR WILL POOL OVER THE REGION THROUGH THIS AFTERNOON IN
ADVANCE OF A COLD FRONT APPROACHING FROM THE OHIO VALLEY. THIS WILL
LEAD TO NUMEROUS SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND THIS
EVENING. THE COLD FRONT WILL PUSH TO OUR SOUTHEAST TONIGHT. DRIER
WEATHER WITH COMFORTABLE HUMIDITY WILL MOVE IN FOR THURSDAY AND
FRIDAY WITH SEASONABLE TEMPERATURES AS HIGH PRESSURE RETURNS. THE
WEEKEND LOOKS HOT AND HUMID WITH THE POSSIBILITY OF A FEW AFTERNOON
THUNDERSTORMS.

&&

.NEAR TERM /UNTIL 11 PM THIS EVENING/...
MID LVL THERMAL RIDGE /H7 TEMPS OF 7-8C/ ACROSS CENTRAL AND ERN
PENN EARLY THIS AFTERNOON WILL SLIDE OFF TO THE MID ATLANTIC COAST
LATE TDY AND ALLOW SEVERAL DEG OF COOLING TO BEGIN. A RATHER
COMPACT/BUT POTENT UPPER TROUGH WILL MOVE FROM LAKE HURON TO THE
UPPER ST. LAWRENCE VALLEY BY THIS EVENING...WITH THE RIGHT ENTRANCE
REGION OF THE MID/UPPER LEVEL JET MAX ROUNDING ITS BASE...BRUSHING
OVER THE ERN HALF OF PENN.

AS THIS INCREASING COOLING/UVVEL ALOFT BECOMES COLLOCATED WITH THE
NEARLY N/S SFC WARM FRONTAL BOUNDARY /ON A LINE FROM NEAR
KELZ...TO KUNV AND KMRB AT 18Z/ EXPECT TSRA TO QUICKLY DEVELOP AND
EXPAND IN AREAL COVERAGE BETWEEN 19-21Z. THE SUSQ VALLEY AND NCENT
MTNS WILL BE THE PRIMARY AREA UNDER THE GUN FOR SVR TSRA LATE
TDY/THIS EVENING...AS THE SFC COLD FRONT NARROWS THE EXTENT OF THE
WARM SECTOR.

POCKETS OF EHI IN THE 2-3 M2/S2 RANGE WILL LEAD TO VARYING STORM
TYPE...WITH ISOLATED SUPERCELLS LIKELY ALONG THE WARM FRONTAL
BOUNDARY NEAR THE SUSQ VALLEY.

A BKN LINE OF STRONG TO SVR/MULTI CELL TSRA WILL OCCUR CLOSER TO
THE APPROACHING CFRONT ACROSS THE LAUREL HIGHLANDS AND CENTRAL
MTNS OF PENN. THIS LATTER LINE OF CONVECTION SHOULD READILY TAP
STRONGER WINDS ALOFT /35-45 KTS IN THE 850-700 MB LAYER/...AND MIX
THEM DOWN TO THE SURFACE AS POTENTIALLY DAMAGING DOWNBURSTS.

MOST OF THE CONVECTION WILL BE WEAKENING/MOVING OFF TO THE SE BY
03Z.

MIN TEMPS TONIGHT WILL RANGE FROM AROUND 50F ACROSS THE NW MTNS...
TO THE MID 60S IN THE LOWER SUSQ VALLEY.

&&

.SHORT TERM /11 PM THIS EVENING THROUGH 6 PM THURSDAY/...
AREAS OF BKN LOW/STRATO CU CLOUDS AND A SPRINKLE OR TWO WILL BE
POSSIBLE ACROSS THE NRN MTS THRU THE NIGHT...AS THE 850/700 MB
THERMAL TROUGH APPROACHES FROM THE NW.

EVERYONE ELSE SHOULD SCT OUT OR EVEN CLEAR OUT FOR AT LEAST SVRL
HOURS LATER TNGT. MOISTURE STAYS HIGH SO SOME FOG POSSIBLE TOO
WHERE SFC WINDS CAN SETTLE TO UNDER 4-6 KTS TWD DAYBREAK.

700 MB TEMPS WARM BACK UP SVRL DEG C...TO 8-9C DURING THE
MIDDAY/AFTERNOON HOURS THURSDAY WHILE THE 850 MB THERMAL TROUGH
SLIDES INTO CENTRAL PENN. THIS SHOULD LEAD TO PERIODS OF
BKN/ALBEIT SHALLOW STRATO CU...CAPABLE OF LITTLE MORE THAN SOME
SPRINKLES OR A BRIEF AFTERNOON SHRA ACROSS THE CENTRAL/NRN MTNS.

THE SOUTHERN AREAS OF THE STATE WILL STAY MSTLY SUNNY.

MAX TEMPS FOR THURSDAY WERE ADJUSTED DOWN SVRL DEG FROM THE
PREVIOUS PACKAGE...TO THE U60S ACROSS THE NRN MTNS...AND LOWER TO
MID 70S ELSEWHERE. THESE TEMPS WILL BE ABOUT 8-9F BELOW NORMAL.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
SFC RIDGE AXIS BECOMING CENTERED ALONG THE APPALACHIANS AND ASSOC
DRY BLW NORMAL PW AIR MASS WILL PROMOTE REFRESHINGLY COOL MIN
TEMPS THURS NIGHT INTO FRIDAY AM WITH PATCHY RVR VLY FOG IN THE
NORTH. HIGH PRES SYS OVERHEAD WILL MIGRATE OFF THE MID-ATLC COAST
THROUGH THE WEEKEND...SETTING UP A PROLONGED PERIOD OF WARM/HUMID
RETURN FLOW AND ABOVE NORMAL TEMPERATURES.

MAIN FEATURE IN THE MEDIUM TO LONG TERM PERIOD WILL BE A
PERSISTENT ANOMALOUS SUBTROPICAL RIDGE OVER THE SOUTH-CENTRAL AND
SOUTHEASTERN U.S. THIS FEATURE WILL CONTINUE VERY WARM/MUGGY
CONDITIONS INTO EARLY NEXT WEEK...RIGHT ON SCHEDULE FOR THE START
OF THE SUMMER SEASON. WITH THE EXCEPTION OF ISOLD AIR MASS
CONVECTION...MAIN WEATHER SYSTEMS WILL BE EJECTING DOWNSTREAM FROM
WCOAST TROUGH WITHIN BELT OF PROGRESSIVE/ZONAL FLOW ALOFT ON THE
NORTHERN PERIPHERY OF THE LARGE SUBTROPICAL RIDGE...SOMEWHAT
ANALOGOUS TO A RING OF FIRE TYPE PATTERN. IN THIS FLOW REGIME...THE
EVOLUTION OF INDIVIDUAL OR SMALL SCALE PERTURBATIONS IS RATHER
DIFFICULT TO ASCERTAIN. THUS WILL CONTINUE TO ADVERTISE MAINLY DRY
CONDITIONS THROUGH THE BULK OF THE PERIOD...OWING TO STRONG UPPER
RIDGE IN THE SOUTH. HPC MANUAL PROGS SHOW A WEAKENING FRONTAL BNDRY
GRADUALLY SINKING SWD FROM THE GREAT LAKES INTO THE MID-ATLC REGION
BY EARLY NEXT WEEK...WHICH MAY ACT AS A FOCUS FOR MORE NUMEROUS
SHOWERS AND TSTORMS.

&&

.AVIATION /00Z THURSDAY THROUGH MONDAY/...
A COLD FRONT WILL SLIDE ACROSS CENTRAL PA EARLY TONIGHT. A BKN
LINE OF SHRA WILL MAKE ITS WAY EASTWARD ACROSS THE AREA THIS
EVENING...BUT THIS ACTIVITY WILL EVENTUALLY SLIP TO THE EAST OF
THE CWA WITH THE FRONT.

LOW CLOUDS THAT LINGERED THROUGH THE DAY ACROSS THE LWR SUSQ
VALLEY WILL FINALLY BE SCOURED OUT WITH THE FRONTAL PASSAGE. SOME
MVFR CEILINGS MAY RETURN TO THE HIGHER TERRAIN OF THE NORTH AND
WEST /BFD AND JST/ LATER TONIGHT...AS LOW CLOUDS COULD DRIFT BACK
INTO THE AREA.

THURSDAY WILL SEE ANY LINGERING LOW CLOUDS SCATTER OUT...WITH VFR
CONDITIONS DEVELOPING AREA-WIDE.

GENERALLY QUIET WX WILL CONTINUE INTO FRI AND EARLY SAT BEFORE A
COLD FRONT APPROACHES THE AREA LATE SAT/EARLY SUN. AFTER
THAT...GENERALLY VFR SUNDAY INTO MONDAY.

OUTLOOK...
FRI...VFR...ASIDE FROM PATCHY AM FOG.
SAT...VFR...ASIDE FROM PATCHY AM FOG AND LATE DAY SHRA/TSRA.
SUN...BECOMING VFR AFTER SHRA/TSRA EARLY.
MON...VFR.

&&

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

&&

SYNOPSIS...LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...LAMBERT
LONG TERM...STEINBUGL
AVIATION...EVANEGO

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE STATE COLLEGE PA
932 AM EDT WED JUN 16 2010

PAZ004-171345-
WARREN-
932 AM EDT WED JUN 16 2010

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...THURSDAY THROUGH TUESDAY.

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

PAZ005-006-010>012-017>019-024>028-033>037-041-042-045-046-049>053-
056>059-063>066-171345-
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-
932 AM EDT WED JUN 16 2010

...SLIGHT RISK FOR SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING...

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA.

.DAY ONE...TODAY AND TONIGHT.

SCATTERED STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED TO DEVELOP
FROM THIS AFTERNOON INTO THE EVENING...AS A COMPLEX FRONTAL SYSTEM
MOVES EASTWARD FROM THE OHIO VALLEY AND THROUGH CENTRAL
PENNSYLVANIA. IN ADDITION TO THE THREAT OF DAMAGING WINDS AND
LARGE HAIL...THE ORIENTATION OF VERTICAL WIND SHEAR TO THE
FRONTAL SYSTEM WILL FAVOR THE FORMATION OF ROTATING STORMS WITH
THE POTENTIAL FOR AN ISOLATED TORNADO.

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

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EVENING.

MS/BL