Severe Thunderstorm Warning 178, NWS State College, PA

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1039 AM EDT THU AUG 19 2004

.SHORT TERM (THROUGH THURSDAY)...

CLOUDS EXTEND OVER MOST OF THE AREA ALONG AND EAST-WEST BAROCLINIC
ZONE. AREA IS PROGGED TO DEVELOP A DECENT AMOUNT OF INSTABILITY AS A
COLD FRONT APPROACHES AND SLOWS. ANOTHER FEATURE IS THE EXPECTATION
OF SOME POTENT SHEAR MADE TO DEVELOP...ESPECIALLY OVER SERN
SECTIONS. OVERALL THUNDER/SEVERE THREAT TODAY WILL LIKELY BE
MITIGATED OVER THE CLOUDY AREAS OF THE NORTH DESPITE THE APPROACHING
FRONT. THERE THE BIGGEST THREAT MAY BE TRAINING ECHOES AND THE
POTENTIAL FOR LOCALIZED FLOODING.

THINK THE BIGGEST SEVERE THREAT WILL BE THE SOUTHERN AND
SOUTHEASTERN AREAS WHERE SUNSHINE AND HIGHER DEWPOINTS...AS WELL AS
PREV MENTIONED SHEAR PROFILES...WILL ALL HAVE THE BEST CHANCE OF
COMING INTO PLAY. RIGHT NOW SUNSHINE IS BREAKING OUT IN THE LAURELS
EAST TO ABOUT CHAMBERSBURG...AND THIS CLEARING IS RACING EAST AND
SHOULD GET THE ENTIRE SRN 1/3 OF THE CWA DESTABILIZING SOON.

WITH THE MCS THAT TRACKED OVER THE STATE EARLIER TODAY...AND THE
APPROACH OF MORE CONVECTION IN THE FAST WESTERLY FLOW...HAVE TO BE
AWARE OF THE POTENTIAL FOR BOUNDARY INTERACTIONS AND ROTATING
STORMS.

&&

.PREVIOUS DISCUSSION...
THE FOLLOWING WAS ORIGINALLY ISSUED AT 303 AM EDT THU AUG 19 2004

AVIATION...

WIDESPREAD MVFR CONDS THIS MORNING DUE TO FOG/LOW CLOUDS...WITH
POCKETS OF OF IFR IN USUAL RIVER VALLEY LOCATIONS SUCH AS
KIPT/KMDT/KSEG. INCREASING MID LEVEL CLOUD DECK THIS MORNING SHOULD
PRECLUDE DENSE FOG FORMATION. WESTERN TERMINALS KBFD/KJST WILL
LIKELY ESCAPE IFR FOG THIS MORNING...HOWEVER MVFR CONDS WILL PREVAIL
WITH BRIEF IFR CONDS POSSIBLE WITH TSRA ACTIVITY SHORTLY AFTER
SUNRISE. ELSEWHERE...WIDESPREAD MFVR CONDS DUE TO HAZE WITH SCT TSRA
THROUGH MUCH OF THE DAY. GUSTY WINDS WILL BE POSSIBLE WITH ANY
STORMS TODAY.

SHORT TERM (TODAY THROUGH SATURDAY NIGHT)...

A VERY ACTIVE WEATHER PERIOD LIES AHEAD THROUGH ROUGHLY THE NEXT 60
HOURS. INITIAL ROUND OF CONVECTION WILL COME THE FIRST HALF OF TODAY
IN THE FORM OF A MCS MOVING QUICKLY EAST ACROSS OHIO (WITH SCTD
STRONG TSRA FORMING JUST TO ITS EAST AND SOUTH). THIS MCS WILL ONLY
WEAKEN TEMPORARILY AS LLVL BOUNDARIES AND SIGNIFICANT DIFFERENTIAL
HEATING ON THE EDGES OF CLOUD COVER LEAD TO AN PRIME SETUP FOR RAPID
DVLPMT OF SVR TSRA DURING THE LATE MORNING CENTRAL AND WEST...AND
BEGINNING EARLY THIS AFTERNOON ACROSS THE SUSQ VALLEY. 0-3KM
HELICITY ACROSS MUCH OF THE REGION IS IN THE 150-200 M2/S2 (OR
HIGHER ACROSS THE SUSQ VALLEY) THROUGH AT LEAST THE MID AFTERNOON
HOURS. THIS TRANSLATES IN SFC-850 HPA SHEAR ON THE ORDER OF +3-5
STANDARD DEVIATIONS ETA SFC BASED CAPES ARE IN EXCESS OF 2000 J/KG
(OVER 3000 J/KG ACROSS THE LWR SUSQ REGION) LATE THIS MORNING
THROUGH THIS AFTERNOON WITH A SW-NE AXIS OF STRONG 850 HPA THETA-E
CONVERGENCE EXTENDING FROM NRN MARYLAND TO NEAR KTHV...KLNS AND KMDT
AT 18Z TODAY. WITH THIS SAID...TODAY SHOULD BE ONE OF THE MORE
SIGNIFICANT SEVERE WEATHER DAYS OF THE SUMMER (UNLESS THE POSSIBLE
LONE LIMITING FACTOR OF WIDESPREAD CLOUD COVER FROM THE MCS LIMITS
THE UPDRAFT STRENGTH OF STORMS). WILL HIGHLIGHT THIS POTENTIALLY
SIGNIFICANT AND WIDESPREAD SEVERE WEATHER VIA AN SPS (SEVERE WEATHER
OUTLOOK)...AND WILL EMPHASIZE THE POTENTIAL FOR ISOLATED TORNADOES
(ESP ACROSS THE SUSQ VALLEY).

FOR TONIGHT...THE COLD FRONT SAGS TO NEAR OR JUST SOUTH OF
INTERSTATE 80 BEFORE STALLING AS THE STRONG UPPER JET MAX EXITS THE
SOUTHERN NEW ENGLAND COAST AND THE UPPER FLOW BEGINS TO BACK BY
ABOUT 20 DEG. THE BOUNDARY RETURNS NORTH THROUGH NEW YORK STATE ON
FRIDAY WITH WEAK SFC WIND DIVERGENCE KEEPING SHOWER ACTIVITY A MIN
THROUGH THE MORNING HOURS. VERY WARM AND HUMID AIRMASS IN PLACE
ACROSS THE REGION FRIDAY AFTERNOON WILL LEAD TO SCTD STRONG TO
POSSIBLY SVR PULSE TSRA. BEST CHC FOR PRECIP ON FRIDAY (AND FRIDAY
NIGHT) WILL BE ACROSS THE NRN HALF OF THE CWA...CLOSER TO THE LLVL
FOCUS OF THE RETREATING BOUNDARY.

HIGH TEMPS FRIDAY WILL ACTUALLY BE ABOUT 5 DEG F OR SO ABOVE NORMAL
(A RARITY FOR THIS SUMMER SO FAR) TOPPING OUT BETWEEN 85 AND 90
THROUGHOUT THE SUSQ VALLEY.

FOR SATURDAY...THE UPPER FLOW CONTINUES TO BACK AS A STRONG SHORT
WAVE MOVES NE UP THE OHIO RIVER VALLEY...ALONG A SLOW MOVING COLD
FRONT. STRONG RIGHT ENTRANCE REGION OF A 120 KT JET ACROSS SE CANADA
WILL PROVIDE SIGNIFICANT LIFT TO THE NORTH OF THE FRONTAL
BOUNDARY...LEADING TO AN EXTENSIVE AREA OF MODERATE RAINFALL. SCTD
STRONG TO SVR TSRA WILL LIKELY FORM SATURDAY AFTERNOON AHEAD OF THIS
FRONT...ACROSS THE EASTERN HALF OF OUR CWA.

LONG TERM (SUNDAY THROUGH WEDNESDAY)...

ONLY REAL CHANGES MADE WERE TO LOWER MIN TEMPS MON AND TUE MORNINGS.
WITH DRY AIRMASS IN PLACE...OVERNIGHT LOWS WILL BE CHILLY. LOOKS
LIKE A DRY PERIOD SETTING UP WITH LOW DEWPOINTS AND NO SIGNIFICANT
STORM SYSTEMS ON THE HORIZON. 500 MB HEIGHTS FORECAST TO GRADUALLY
RISE NEXT WEEK...AS LONG WAVE PATTERN SHIFTS FOR THE FIRST TIME IN A
WHILE. THEREFORE...WILL CONTINUE DRY FORECAST THROUGH THE PERIOD.
&&

.CTP WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
&&

SHORT TERM (UPDATE)...LA CORTE

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE STATE COLLEGE PA
547 AM EDT THU AUG 19 2004

PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-049>053-
056>059-063>066-200947-
ADAMS PA-BEDFORD PA-BLAIR PA-CAMBRIA PA-CAMERON PA-CLEARFIELD PA-
COLUMBIA PA-CUMBERLAND PA-DAUPHIN PA-ELK PA-FRANKLIN PA-FULTON PA-
HUNTINGDON PA-JUNIATA PA-LANCASTER PA-LEBANON PA-MCKEAN PA-
MIFFLIN PA-MONTOUR PA-NORTHERN CENTRE PA-NORTHERN CLINTON PA-
NORTHERN LYCOMING PA-NORTHUMBERLAND PA-PERRY PA-POTTER PA-
SCHUYLKILL PA-SNYDER PA-SOMERSET PA-SOUTHERN CENTRE PA-
SOUTHERN CLINTON PA-SOUTHERN LYCOMING PA-SULLIVAN PA-TIOGA PA-
UNION PA-WARREN PA-YORK PA-
547 AM EDT THU AUG 19 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA.

.DAY ONE...TODAY:

A COLD FRONT STRETCHED FROM CHICAGO TO NEAR TORONTO WILL MOVE
SOUTHEAST TOWARD PENNSYLVANIA TODAY. SCATTERED STRONG TO SEVERE
THUNDERSTORMS WILL FORM THIS AFTERNOON...FOLLOWING A ROUND OF SHOWERS
AND THUNDERSTORMS ACROSS MUCH OF THE CENTRAL AND WEST THIS MORNING.
WINDS ALOFT WILL ALSO BE STRENGTHENING...AND THIS WILL RESULT IN THE
POTENTIAL FOR ISOLATED TORNADOES WITH A FEW OF THE SEVERE
THUNDERSTORMS...ESPECIALLY ACROSS THE SUSQUEHANNA VALLEY.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY:

THE COLD FRONT AFFECTING THE REGION ON THURSDAY WILL STALL OUT ACROSS
CENTRAL PENNSYLVANIA THURSDAY NIGHT BEFORE RETREATING AS A WARM FRONT
ON FRIDAY. A SECOND...AND STRONGER COLD FRONT WILL SWEEP ACROSS THE
COMMONWEALTH SATURDAY AND SATURDAY NIGHT. SCATTERED SEVERE
THUNDERSTORMS ARE POSSIBLE BOTH FRIDAY AND SATURDAY...ESPECIALLY
DURING THE AFTERNOON AND EARLY EVENING HOURS.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1134 AM EDT THU AUG 19 2004

PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-049>053-
056>059-063>066-200000-
ADAMS PA-BEDFORD PA-BLAIR PA-CAMBRIA PA-CAMERON PA-CLEARFIELD PA-
COLUMBIA PA-CUMBERLAND PA-DAUPHIN PA-ELK PA-FRANKLIN PA-FULTON PA-
HUNTINGDON PA-JUNIATA PA-LANCASTER PA-LEBANON PA-MCKEAN PA-
MIFFLIN PA-MONTOUR PA-NORTHERN CENTRE PA-NORTHERN CLINTON PA-
NORTHERN LYCOMING PA-NORTHUMBERLAND PA-PERRY PA-POTTER PA-
SCHUYLKILL PA-SNYDER PA-SOMERSET PA-SOUTHERN CENTRE PA-
SOUTHERN CLINTON PA-SOUTHERN LYCOMING PA-SULLIVAN PA-TIOGA PA-
UNION PA-WARREN PA-YORK PA-
1134 AM EDT THU AUG 19 2004

...SEVERE WEATHER OUTLOOK...

THERE WILL BE A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
FOR MUCH OF
CENTRAL PENNSYLVANIA. A COLD FRONT MOVING SOUTH ACROSS THE GREAT
LAKES WILL TRIGGER SHOWERS AND THUNDERSTORMS ACROSS THE AREA. SOME
THUNDERSTORMS COULD BECOME SEVERE CAUSING DAMAGING WIND GUSTS AND
LARGE HAIL.

STAY TUNED TO NOAA WEATHER RADIO AND OTHER LOCAL MEDIA FOR FURTHER
DETAILS OR UPDATES.

FOR ADDITIONAL WEATHER INFORMATION...CHECK OUR WEB SITE AT...
WWW.ERH.NOAA.GOV/CTP

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
233 PM EDT THU AUG 19 2004

PAZ024>028-033>036-050-056-063-064-200000-
ADAMS PA-BEDFORD PA-BLAIR PA-CAMBRIA PA-CUMBERLAND PA-FRANKLIN
PA-FULTON PA-HUNTINGDON PA-JUNIATA PA-MIFFLIN PA-PERRY PA-SNYDER
PA-SOMERSET PA-
233 PM EDT THU AUG 19 2004

...A SEVERE THUNDERSTORM WATCH IS IN EFFECT UNTIL 800 PM EDT
THURSDAY EVENING FOR THE FOLLOWING COUNTIES IN CENTRAL
PENNSYLVANIA...

ADAMS...BEDFORD...BLAIR...CAMBRIA...CUMBERLAND...FRANKLIN...FULTON...
HUNTINGDON...JUNIATA...MIFFLIN...PERRY...SNYDER AND SOMERSET.

A SEVERE THUNDERSTORM WATCH MEANS THAT SEVERE THUNDERSTORMS ARE
POSSIBLE IN AND CLOSE TO THE WATCH AREA...PRODUCING DAMAGING WINDS...
LARGE HAIL AND FREQUENT LIGHTNING.