Severe Thunderstorm Warning 26, NWS State College, PA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
546 PM EDT FRI MAY 10 2013

.SYNOPSIS...
A COLD FRONT WILL MOVE THROUGH THE AREA LATER TONIGHT...FOLLOWED
BY A SECONDARY COLD FRONT LATER SATURDAY THAT WILL DELIVER MUCH
COOLER AIR INTO THE REGION FOR SUNDAY INTO EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH SATURDAY/...
INCREASING LARGE SCALE LIFT WAS MOVING INTO SOUTHERN AND WRN
SECTIONS OF OUR CWA...AHEAD OF A MID/UPPER SHORTWAVE RACING NE
ACROSS THE UPPER OHIO VALLEY. THIS ENERGY ALOFT WILL BE SPREADING
OVER A FAIRLY LARGE AREA OF MAX INSTABILITY...EXTENDING FROM THE NW
MTNS TO THE LOWER SUSQ VALLEY AT 2145Z /WHERE MUCAPES WERE JUST OVER
1000 J/KG BENEATH THIN SPOTS IN THE BKN-OVC CIRRUS SHIELD/.

TSRA CORES HAVE BEEN JUST UNDER SEVERE LIMITS FOR THE MOST PART SO
FAR...AND I AGREE WITH THE LATEST SWOMCD 624 ISSUED AT 411 PM THAT
LIMITED INSTABILITY WILL KEEP ANY SVR THREAT QUITE ISOLATED.

MINI BOWS...AND BRIEF UPWARD PULSES TO THE TSRA CORES WILL LIKELY BE
HANDLED THIS EVENING WITH NUMEROUS SPECIAL WEATHER STATEMENTS FOR
WIND GUSTS BETWEEN 40-50 MPH...AND A FEW INSTANCES OF DIME-NICKEL
SIZE HAIL.

THE LONE SVR TSRA WARNING ISSUED EARLIER /AND VERIFIED WITH QUARTER
SIZE HAIL IN WESTERN WARREN COUNTY/...WAS NESTLED WITHIN A MORE
DEFINED RIBBON OF LLVL THETA-E CONVERGENCE AND SWRLY 850 WIND CORE
OF AROUND 40 KTS.

EXPECT WIDESPREAD SHOWERS AND AREAS OF EMBEDDED TSRA TO SPREAD NE
ACROSS THE REGION THROUGH EARLY TONIGHT.

LATEST TIMING ON THE COLD FRONT SUGGESTS IT WILL BE JUST ENTERING
MY WESTERN ZONES SHORTLY AFTER MIDNIGHT.

ALTHOUGH NUMEROUS SHOWERS WILL LIKELY PERSIST THROUGH THE OVERNIGHT
HOURS...THE CHC FOR TSRA WILL MARKEDLY DECREASE AFTER 03Z. A
WIDESPREAD BENEFICIAL RAINFALL ON THE ORDER OF ONE HALF TO ONE INCH
SEEMS LIKELY IN MOST AREAS...WITH LOCALLY HEAVIER AMOUNTS POSSIBLE
IN STRONGER STORMS.

THE OVERNIGHT WILL BE MILD WITH LOWS GENERALLY IN THE MID 50S TO
LOWER 60S AHEAD OF THE COLD FRONT.

&&

.SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/...
THE UPPER-LEVEL PATTERN IS FCST TO AMPLIFY THROUGH THE SHORT RANGE
PERIOD...AS AN INTENSE CANADIAN SHORTWAVE TROUGH DIGS ESEWD ACROSS
THE UPPER GREAT LAKES AND HELPS TO CARVE OUT AN ANOMALOUS 500-MB
TROUGH OVER THE ERN U.S. A LARGE AREA OF HGT FALLS AND BROAD
/UNSEASONABLY COLD/ CYCLONIC FLOW ALOFT WILL EVENTUALLY OVERSPREAD
THE NERN CONUS BY THE END OF THE WEEKEND. AT THE SFC...THE LEADING
COLD FRONT ASSOCD WITH A LOW IN THE ST. LAWRENCE VLY SHOULD PUSH
SLOWLY EWD ACRS CENTRAL PA ON SATURDAY...WITH THE MAIN SYNOPTIC COLD
FROPA - MARKING THE LEADING EDGE OF THE UNSEASONABLY COLD AIR -
OCCURRING ON SUNDAY (MOTHER'S DAY).

STILL EXPECT SW-NE ORIENTED BAND OF SHOWERS TO ACCOMPANY THE LEADING
COLD FRONT...COINCIDING WITH AXIS OF RELATIVELY HIGH LO-LVL MSTR
CONVERGENCE AND AXIS OF +1-2 SIGMA PWAT. THE THREAT OF SVR STORMS
/BASED ON THE SPC DAY 2 OUTLOOK/ HAS SHIFTED S/EWD TO XTRME SERN PA
THE NC/MD/VA PIEDMONT/COASTAL PLAIN. THE PLUME OF ABOVE NORMAL
MSTR SHIFTS QUICKLY TO THE COAST BY SAT EVE...AND THUS ANTICIPATE
LOWER QPF AND DIMINISHING TREND /FROM WEST-TO-EAST/ TO THE SHOWER
ACTIVITY BY SATURDAY NIGHT. DAY 2 QPF IS 0.25-0.50 INCH OVER THE
SE ZONES...WITH LESSER AMTS TO THE NW. THE BROAD/COLD CYCLONIC
FLOW COMBINED WITH COLD POCKET ALOFT WILL CONTRIBUTE TO SCT RAIN
SHOWERS DURING THE DAY ON SUNDAY WITH EVEN SOME RAIN/SNOW SHOWERS
POSSIBLE IN THE NW MTNS AND SUN NGT.

AS FOR TEMPERATURES...SATURDAY WILL BE THE TRANSITION DAY WITH
POTENTIAL FOR SHARP NW-SE GRADIENT EITHER SIDE OF THE COLD FRONT.
SUNDAY LOOKS BREEZY AND COOL WITH TEMPS WELL-BELOW MID MAY CLIMATE
NORMALS.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
THE HIGH-AMPLITUDE FLOW EARLY IN THE PERIOD WILL TRANSITION TOWARD A
FLATTER/MORE PROGRESSIVE LG SCALE PATTERN INTO THE MEDIUM RANGE AS
QUASI-ZONAL ORIENTED PACIFIC FLOW EXTENDS EWD ALONG THE US/CANADIAN
BORDER...FLATTENING THE WRN RIDGE-ERN TROUGH CONFIGURATION. THE
DEAMPLIFICATION AND LOWER AMPLITUDE NATURE OF THE FLOW IN TIME
TEMPERS FCST CONFIDENCE AND INCREASES UNCERTAINTY IN THE DETAILS.

HIGH PRES /WITH ORIGINS IN THE NW TERRITORIES/ WILL DIVE SWD THRU
THE N-CENTRAL PLAINS INTO THE MID-SOUTH/TN VLY BY MONDAY...THEN
MIGRATE SEWD ACRS THE SRN APPLCHNS AND OFF THE SE COAST INTO THE
MIDDLE OF NEXT WEEK. THE GLOBAL GUIDANCE SHOWS THE DEEP ERN TROUGH
LIFTING OUT OF THE MID-ATLC REGION ON TUE WITH 500MB HGTS REBOUNDING
WED-THR. OPRN GFS/ECMWF AND THEIR ENS MEANS BECOME OUT OF PHASE
LATE IN THE PERIOD.

THE MAIN FOCUS THIS PERIOD IS ON POTENTIAL FROST/FREEZE EARLY
NEXT WEEK...ESPECIALLY WHERE THE GROWING SEASON IS UNDERWAY ALONG
AND TO THE SE OF THE I-99/RTE 220 CORRIDOR. MON NGT-TUE AM STILL
LOOKS TO BE THE MOST FAVORABLE TIME FOR A NPW HEADLINE BASED ON
CONSENSUS OF 5/10 00/12Z MOS PRODUCTS /INCLUDING THE EXPERIMENTAL
OPRN/MEAN/MEDIAN ECMWF GUIDANCE/. SUN NGT-MON AM ALSO LOOKS CHILLY
BUT FEEL THERE SHOULD BE ENOUGH OF A POST-FRONTAL GRADIENT TO KEEP
A LGT/SUSTAINED NW WIND.

DAYTIME HIGHS SHOULD BOTTOM OUT ON MONDAY WITH MEAN MAX/MIN TEMP
DEPARTURES RUNNING 15-20F BELOW NORMAL. READINGS MAY APPROACH DAILY
RECORD NIGHTTIME LOWS /OR PERHAPS RECORD LOW MAXES ON MONDAY/.

IN TERMS OF PCPN...THE ANOMALOUSLY COLD AIR ALOFT AND UPPER LEVEL
TROUGH PASSAGE SHOULD PROMOTE DIURNALLY-DRIVEN INSTABILITY SHOWERS
INTO MONDAY BEFORE SFC RIDGE ARRIVES MON NGT-TUE. AFTER A COOL START
TO THE WEEK...EXPECT TEMPS TO MODERATE THROUGH THE MIDDLE TO LATTER
PART OF NEXT WEEK WITH TEMPS LKLY GETTING BACK INTO THE 70S BY
THURS. USED A CONSENSUS BLEND FOR POPS DAYS 5-8 LEANING TOWARD THE
ECMWF-BASED MOS PRODUCTS.

&&

.AVIATION /22Z FRIDAY THROUGH WEDNESDAY/...
WEAK DISTURBANCE MOVING THRU CENTRAL/EASTERN PA AS OF MID DAY WILL
KEEP A FEW SHOWERS AND POSSIBLY AN ISOLATED THUNDERSTORM IN THE
AREA THROUGH MID AFTERNOON...BUT THESE WILL NOT CAUSE MUCH MORE
THAN BRIEF REDUCTIONS IN FLYING CONDITIONS AS THEY MOVE OVER THE
REGIONAL AIRPORTS.

WE WILL SEE A LULL IN THE SHOWERS INTO MID AFTERNOON...WHEN NEW
CONVECTION ASSOCIATED WITH A COLD FRONT OVER THE OHIO VALLEY
BEGINS MOVING INTO THE REGION FOR THE LAST PART OF THE
AFTERNOON...AFTER 20-21Z...AND CONTINUE INTO THE EVENING. SOME OF
THE THUNDERSTORMS COULD BE LOCALLY SEVERE WITH STRONG WIND GUSTS
AND PERHAPS HAIL.

THE OVERNIGHT WILL SEE WIDESPREAD IFR/MVFR WITH NUMEROUS SHOWERS
AND THUNDERSTORMS CONTINUING INTO SATURDAY MORNING.

THE FIRST COLD FRONT CAUSING THE SHOWERS AND STORMS WILL ENTER
NWRN PA AROUND MIDNIGHT...AND PASS THROUGH SERN PA SATURDAY
MORNING. A SECOND COLD FRONT WILL TRAVERSE THE REGION TOMORROW
AFTERNOON AND EARLY EVENING...POSSIBLY TRIGGERING MORE SHOWERS OR
ISOLATED THUNDERSTORMS.

.OUTLOOK...

SAT...SLOWLY IMPROVING CONDITIONS IN THE WAKE OF THE COLD FRONT.

SUN-TUE...NO SIG WX.

WED...MVFR/SHOWERS WITH AN APPROACHING WARM FRONT.

&&

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

&&

SYNOPSIS...LA CORTE/LAMBERT
NEAR TERM...LAMBERT
SHORT TERM...STEINBUGL
LONG TERM...STEINBUGL
AVIATION...LA CORTE

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE STATE COLLEGE PA
336 PM EDT FRI MAY 10 2013

PAZ004>006-010>012-017-018-024-033-037-041-042-111945-
WARREN-MCKEAN-POTTER-ELK-CAMERON-NORTHERN CLINTON-CLEARFIELD-
NORTHERN CENTRE-CAMBRIA-SOMERSET-TIOGA-NORTHERN LYCOMING-SULLIVAN-
336 PM EDT FRI MAY 10 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON AND EVENING. THE MAIN SEVERE WEATHER THREATS WILL BE
DAMAGING WINDS AND LARGE HAIL.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

THE PROBABILITY OF WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

PAZ019-025>028-034>036-045-046-049>053-056>059-063>066-111945-
SOUTHERN CENTRE-BLAIR-HUNTINGDON-MIFFLIN-JUNIATA-BEDFORD-FULTON-
FRANKLIN-SOUTHERN CLINTON-SOUTHERN LYCOMING-UNION-SNYDER-MONTOUR-
NORTHUMBERLAND-COLUMBIA-PERRY-DAUPHIN-SCHUYLKILL-LEBANON-CUMBERLAND-
ADAMS-YORK-LANCASTER-
336 PM EDT FRI MAY 10 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON AND EVENING. THE MAIN SEVERE WEATHER THREATS WILL BE
DAMAGING WINDS AND LARGE HAIL.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY.

UNSEASONABLY COLD AIR WILL BRING THE POTENTIAL FOR FROST AND
FREEZING TEMPERATURES EARLY NEXT WEEK.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

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SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
622 PM EDT FRI MAY 10 2013

PAZ056-057-063>065-102300-
ADAMS PA-CUMBERLAND PA-DAUPHIN PA-PERRY PA-YORK PA-
622 PM EDT FRI MAY 10 2013

...STRONG THUNDERSTORMS WILL AFFECT THE HARRISBURG METRO AREA...

AN AREA OF STRONG THUNDERSTORMS COVERED PORTIONS OF ADAMS...
CUMBERLAND...DAUPHIN...PERRY AND YORK COUNTIES AT 617 PM EDT. THE
STRONG THUNDERSTORMS WERE GENERALLY MOVING NORTHEAST AT 35 MPH.

WIND GUSTS TO 45 OR 50 MPH ARE POSSIBLE WITH THESE STRONG
THUNDERSTORMS.

NOTABLE LOCATIONS AFFECTED INCLUDE HARRISBURG INTERNATIONAL
AIRPORT...HERSHEY PARK...SKI ROUNDTOP SKI AREA...CITY ISLAND...
MESSIAH COLLEGE...PENN STATE COLLEGE OF MEDICINE...PENN STATE
DICKINSON SCHOOL OF LAW AND PENN STATE HARRISBURG.

LAT...LON 4050 7732 4063 7696 4060 7692 4064 7681
      4065 7670 4048 7666 4048 7668 4021 7659
      4013 7672 3987 7674 3986 7709

FORECASTER: DANGELO