Flood in Pennsylvania, August 21, 2004

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1005 PM EDT FRI AUG 20 2004

.SHORT TERM (REST OF TONIGHT THROUGH SATURDAY)...

VERY ACTIVE NIGHT (SEVERE WEATHER-WISE) ACROSS THE CWA. SVR TSRA
WATCH #771 (IN EFFECT UNTIL 11 PM EDT)...HAS JUST BEEN CANCELLED.

STALLED OUT FRONTAL BOUNDARY ACROSS NWRN PENN...COMBINED WITH THE
SOUTHERN EDGE OF A MID/UPR LEVEL WIND MAX...AND GOOD SFC BASED
INSTABILITY THROUGH THE EARLY EVENING HOURS (W/SFC TEMPS IN THE 80S)
ALLOWED SEVERAL AREAS OF STRONG TO SEVERE CONVECTION TO BLOSSOM AND
TRACK NE ACROSS CENTRAL PENN AND THE SUSQ VALLEY. LOCALIZED FLASH
FLOODING ALSO OCCURRED FROM SEVERAL ROUNDS OF TSRA ACROSS UNION
COUNTY.

FOR THE REST OF THE OVERNIGHT AND EARLY SATURDAY...A WAVE ALONG THE
QUASI STNRY FRONT (1010 MB) WILL MOVE NE FROM THE MIDDLE OHIO RIVER
VALLEY AND CONTINUE PERIODS OF RAIN (BRIEFLY MODERATE TO HEAVY)
OVERNIGHT...AND INTO THE MID MORNING HOURS ACROSS THE SUSQ VALLEY.

UPDRAFT STRENGTH OF THE TSRA HAS DIMINISHED GREATLY OVER PAST FEW
HOURS (THOUGH A LINE OF STRONG TSRA W/GUSTS TO AROUND 40 MPH IS
CROSSING THE LWR SUSQ VALLEY E OF KMDT ATTM)...AND THEYLL BE MAINLY
HEAVY RAIN/LIGHTNING MAKERS AS THE MAIN LINE OF CONVECTION EXITS THE
LOWER SUSQ VALLEY BY 04Z.

BASIN AVERAGE QPF WILL BE BETWEEN 0.50-0.75 WITH LOCALLY HIGHER
AMOUNTS JUST TO THE NORTH OF A LINE FROM KIPT TO KJST. THUS...THE
FLASH FLOOD WATCH OUT UNTIL 4 AM WILL CONTINUED TO BE CARRIED WITH
THIS LATE EVENING UPDATE.

SKIES WILL CLEAR OUT NICELY ACROSS THE WEST DURING THE
AFTERNOON...WITH ANY SHOWERS CONFINED PRIOR TO 13 OR 14Z. SHOWERS
WILL LINER ACROSS THE LOWER SUSQ REGION UNTIL EARLY AFTERNOON AS A
FINAL VORT MAX MOVES EAST ACROSS THE STATE.

&&

.PREVIOUS DISCUSSION...
THE FOLLOWING WAS ORIGINALLY ISSUED AT 253 PM EDT FRI AUG 20 2004

AVIATION...

SHWRS/TSTORMS WILL AFFECT THE AREA INTO SAT MORNING. VFR AND MVFR
WILL PREVAIL...WITH ISOLATED IFR IN RA/TSRA. COLD FRONT PASSES
THROUGH AREA TOM AFT...SIGNALING IMPROVING CONDITIONS AFT 18Z. HIGH
PRESSURE THEN BUILDS IN BEHIND THE FRONT...WITH MAINLY VFR
CONDITIONS.

SHORT TERM (TONIGHT THROUGH SUNDAY)...

SVR TSTORM WATCH ISSUED FOR MOST OF CWA EXCLUDING SOUTHERN TIER.
SHWRS/TSTORMS DEVELOPING RAPIDLY AS OF 18Z...WILL ALSO ISSUE FLASH
FLOOD WATCH FOR MOST OF CWA EXCLUDING LOWER SUSQ. WEAK STATIONARY
BOUNDARY LOCATED ACROSS THE NORTHERN TIER CONTINUED FOCAL POINT FOR
THIS AFTERNOON. SOUTH OF THIS BOUNDARY...SFC HEATING HAS ALLOWED FOR
QUICK ATMOSPHERIC DESTABILIZATION...WITH MIXED LAYER CAPES BTWN
1500-3000 J/KG. STRONG W/SW LLVL JET (30-40KTS) AND DECENT SHEAR
WILL SUPPORT STRONG TO SVR THUNDERSTORM DEVELOPMENT. HODOGRAPHS ALSO
INDICATE POTENTIAL FOR THE FORMATION OF MULTI-CELL/BOW TYPE ECHOS.
WITH INGREDIENTS COMING TOGETHER...TORRENTIAL DOWNPOURS...LARGE
HAIL...FREQUENT CLOUD TO GROUND LIGHTING AND STRONG GUSTY WINDS
(60MPH+) MAY ACCOMPANY TSTORMS. WITH PLENTY OF LEFTOVER OUTFLOW
BOUNDARIES...SOME STORMS WILL HAVE THE POTENTIAL TO PRODUCE
TORNADOES. THIS BOUNDARY WILL WAVER ALONG THE PA/NY BORDER FOR MOST
OF THIS AFT CONTINUING TO TRIGGER SHWRS/TSTORMS. LOW PRESSURE CENTER
TRACKING THROUGH THE OHIO VALLEY WILL ALSO ENHANCE ACTIVITY LATER
THIS EVENING/OVERNIGHT AS BEST DYNAMICS WILL BE IN PLACE. PWS
(1.75+) AND SFC DEWPOINTS IN THE UPPER 60S AND LOW 70S WILL PROVIDE
PLENTY OF LLVL MOISTURE TO FUEL SHWRS/TSTORMS.

ETA/GFS SOLUTIONS DIFFER SLIGHTLY...HOWEVER LOOKING AT MOS GUIDANCE
WILL GO WITH LKLY/CAT POPS THROUGH 12Z SAT. LOW PRESSURE CENTER
TRACKS THROUGH OHIO VALLEY...AND INTO W PA TOWARD MORNING.
ASSOCIATED COLD FRONT PUSHES THROUGH PA BY 18Z SAT...AS AREA OF HIGH
PRESSURE BEGINS TO BUILD IN. THIS HIGH DOMINATES WEATHER THROUGH THE
LATTER HALF OF THE WEEK...AS UPPER TROUGH OVER ESTRN US BEGINS TO
LIFT OUT AND RIDGING BEGINS.

LONG TERM (SUNDAY NIGHT THROUGH FRIDAY)...

EXTENDED FORECAST WILL FEATURE A TRANSITION FROM THIS WEEKENDS
COOLER AND DRIER CONDITIONS TO AN ACTUAL SUMMERTIME PATTERN WITH
LONG RANGE MODELS INDICATING A TRUE BERMUDA HIGH BRINGING AN
EXTENDED PERIOD OF WARMTH AND HUMIDITY TO THE REGION FOR THE MIDDLE
TO LATER PART OF NEXT WEEK AND BEYOND. UPPER RIDGE AXIS BUILDS TO
OUR EAST BY MIDWEEK WITH DAILY CHANCES FOR SHRA/TSRA AT THE DIURNAL
MAXIMUM. TEMPERATURES SHOULD BE NEAR TO ABOVE NORMAL THROUGHOUT THE
PERIOD.
&&

.CTP WATCHES/WARNINGS/ADVISORIES...
PA...FLASH FLOOD WATCH FOR ZONES PAZ004>006-010>012-017>019-
     024>028-033>035-037-041-042-045-046-049>053 UNTIL 4 AM EDT.
&&

SHORT TERM (UPDATE)...LAMBERT

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE STATE COLLEGE PA
332 AM EDT FRI AUG 20 2004

PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-049>053-
056>059-063>066-210731-
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-
332 AM EDT FRI AUG 20 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR CENTRAL PENNSYLVANIA.

.DAY ONE...TODAY:

A LOW PRESSURE SYSTEM WILL MOVE NORTHEAST ALONG A STALLED-OUT FRONT
OVER THE UPPER OHIO VALLEY TODAY.  THE FRONT WILL LIFT SLIGHTLY
NORTHWARD TODAY AS A WARM FRONT.  THE HOT AND HUMID AIR FLOWING UP
FROM THE SOUTH WILL FUEL SHOWERS AND THUNDERSTORMS TODAY...MAINLY
THIS AFTERNOON AND INTO THE NIGHT.  SEVERE THUNDERSTORMS WITH
DAMAGING WINDS...AND ISOLATED TORNADOES...ARE POSSIBLE THIS AFTERNOON
AND EVENING...MAINLY OVER THE NORTHERN HALF OF CENTRAL PENNSYLVANIA.

HEAVY RAIN IS POSSIBLE FROM THIS AFTERNOON THROUGH THE NIGHT IN
NORTHWESTERN PENNSYLVANIA...ALONG THE EXPECTED TRACK OF THE SURFACE
LOW PRESSURE SYSTEM.  MINOR FLOODING IS A POSSIBILITY AS THE
THUNDERSTORMS MAY CONTAIN TORRENTIAL RAINS...BUT THE AREA WHERE THE
HEAVIEST RAIN IS EXPECTED HAS BEEN RATHER DRY RECENTLY.

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

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

SPOTTER CALL TO ACTION STATEMENT...

SPOTTER ACTIVATION IS LIKELY.

PRELIMINARY LOCAL STORM REPORT ... SUMMARY
NATIONAL WEATHER SERVICE STATE COLLEGE PA
836 PM EDT FRI AUG 20 2004

..TIME...   ...EVENT...     ...CITY LOCATION...      ...LAT.LON...
..DATE...   ....MAG....     ..COUNTY LOCATION...ST.. ...SOURCE....
            ..REMARKS..

0210 PM     HAIL             2 S PORT MATILDA        40.77N 78.05W
08/20/2004  0.75 INCH        CENTRE             PA   PUBLIC

0225 PM     HAIL             1 S PLEASANT GAP        40.85N 77.74W
08/20/2004  0.75 INCH        CENTRE             PA   LAW ENFORCEMENT

            PENNY SIZE HAIL AND 70 MPH WINDS AT ROCKVIEW STATE PRISON

0346 PM     HAIL             MUNCY                   41.20N 76.79W
08/20/2004  0.88 INCH        LYCOMING           PA   TRAINED SPOTTER

            DIME TO NICKEL SIZE HAIL

0405 PM     HAIL             6 W WESTOVER            40.75N 78.80W
08/20/2004  1.00 INCH        CLEARFIELD         PA   PUBLIC

0505 PM     HAIL             PHILIPSBURG             40.89N 78.21W
08/20/2004  0.88 INCH        CENTRE             PA   TRAINED SPOTTER

0545 PM     TSTM WND DMG     MERCERSBURG             39.83N 77.90W
08/20/2004                   FRANKLIN           PA   EMERGENCY MNGR

            TREES AND POWER LINES DOWN

0550 PM     TSTM WND DMG     ROXBURY                 40.09N 77.67W
08/20/2004                   FRANKLIN           PA   EMERGENCY MNGR

            TREES AND POWER LINES DOWN

0555 PM     TSTM WND DMG     1 SE CHAMBERSBURG       39.92N 77.64W
08/20/2004                   FRANKLIN           PA   EMERGENCY MNGR

            TREE DOWN ON A HOUSE

0740 PM     TSTM WND DMG     PENFIELD                41.21N 78.60W
08/20/2004                   CLEARFIELD         PA   PUBLIC

            POWER LINES DOWN

0746 PM     HAIL             GREENCASTLE             39.79N 77.73W
08/20/2004  1.00 INCH        FRANKLIN           PA   TRAINED SPOTTER

0750 PM     FLASH FLOOD      1 N MIFFLINBURG         40.93N 77.05W
08/20/2004                   UNION              PA   NWS EMPLOYEE

            SEVERAL CREEKS OVERFLOWING ROADS AND MAKING THEM
            IMPASSABLE

0755 PM     HAIL             1 S GREENCASTLE         39.78N 77.73W
08/20/2004  1.25 INCH        FRANKLIN           PA   PUBLIC

            UNSAFE TO MEASURE WHILE FALLING SO ACTUAL SIZE MAY HAVE
            BEEN LARGER

0755 PM     FUNNEL CLOUD     1 S GREENCASTLE         39.78N 77.73W
08/20/2004                   FRANKLIN           PA   PUBLIC

            ROTATING FUNNEL DID NOT TOUCH DOWN

&&

RH

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
900 PM EDT FRI AUG 20 2004

PAZ058-210200-
SCHUYLKILL-
900 PM EDT FRI AUG 20 2004

...A STRONG THUNDERSTORM WILL AFFECT SCHUYLKILL COUNTY...

AT 854 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 2 MILES SOUTH OF SCHUYLKILL HAVEN...MOVING
NORTHEAST AT 25 MPH. THE THUNDERSTORM WILL BE NEAR MIDDLEPORT AROUND
910 PM...NEW RINGGOLD...TUSCARORA AROUND 915 PM...TAMAQUA AROUND 930
PM...SNYDERS AND COALDALE AROUND 935 PM.

WIND GUSTS TO 40 MPH AND SMALL HAIL ARE POSSIBLE WITH THIS STORM.

RXR

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
920 PM EDT FRI AUG 20 2004

PAZ057-059-065-066-210245-
DAUPHIN-LANCASTER-LEBANON-YORK-
920 PM EDT FRI AUG 20 2004

...STRONG THUNDERSTORMS WILL AFFECT YORK...DAUPHIN...LANCASTER...AND
LEBANON COUNTIES...

AT 911 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM 6 MILES NORTHWEST
OF MECHANICSBURG TO 11 MILES WEST OF WEIGELSTOWN TO 12 MILES
SOUTHWEST OF GETTYSBURG...MOVING EAST AT 30 MPH. THE THUNDERSTORMS
WILL BE NEAR ROCKVILLE AROUND 925 PM...LEWISBERRY...HARRISBURG...
DOVER AROUND 930 PM...COLONIAL PARK...LINGLESTOWN...WEIGELSTOWN...
VALLEY GREEN AROUND 935 PM...SPRING GROVE AND RUTHERFORD HEIGHTS
AROUND 940 PM.

WIND GUSTS TO 35 MPH AND FREQUENT...DANGEROUS LIGHTNING ARE
POSSIBLE WITH THESE STORMS.

RXR

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
934 PM EDT FRI AUG 20 2004

PAZ064-210200-
ADAMS-
934 PM EDT FRI AUG 20 2004

...A STRONG THUNDERSTORM WILL AFFECT ADAMS COUNTY...

AT 925 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
STRONG THUNDERSTORM 7 MILES SOUTH OF GETTYSBURG...MOVING NORTHEAST AT
30 MPH. THE THUNDERSTORM WILL BE NEAR BONNEAUVILLE...LITTLESTOWN
AROUND 940 PM...MCSHERRYSTOWN AROUND 945 PM...NEW OXFORD...
HEIDLERSBURG AROUND 950 PM...ABBOTTSTOWN AROUND 955 PM AND LAKE MEADE
AROUND 1000 PM.

WIND GUSTS TO 45 MPH AND HAIL UP TO ONE HALF OF AN INCH ARE POSSIBLE
WITH THIS STORM.

RXR

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1025 PM EDT FRI AUG 20 2004

PAZ005-006-010>012-017>019-024>028-037-041-042-045-046-049>053-
056>059-063-210245-
BLAIR PA-CAMBRIA PA-CAMERON PA-CLEARFIELD PA-COLUMBIA PA-CUMBERLAND
PA-DAUPHIN PA-ELK PA-HUNTINGDON PA-JUNIATA 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-SOUTHERN CENTRE PA-SOUTHERN CLINTON
PA-SOUTHERN LYCOMING PA-SULLIVAN PA-TIOGA PA-UNION PA-
1025 PM EDT FRI AUG 20 2004

...THE SEVERE THUNDERSTORM WATCH HAS BEEN CANCELED FOR THE FOLLOWING
COUNTIES...

BLAIR...CAMBRIA...CAMERON...CENTRE...CLEARFIELD...CLINTON...
COLUMBIA...CUMBERLAND...DAUPHIN...ELK...HUNTINGDON...JUNIATA...
LEBANON...LYCOMING...MCKEAN...MIFFLIN...MONTOUR...NORTHUMBERLAND...
PERRY...POTTER...SCHUYLKILL...SNYDER...SULLIVAN...TIOGA AND UNION.

ALTHOUGH SHOWERS AND A FEW THUNDERSTORMS WILL CONTINUE INTO THE
OVERNIGHT HOURS...THE THREAT OF SEVERE WEATHER HAS ENDED ACROSS
THE REGION THIS EVENING.

RXR/BG

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE STATE COLLEGE PA
112 AM EDT SAT AUG 21 2004

PAZ057-059-065-210600-
DAUPHIN-LEBANON-YORK-
112 AM EDT SAT AUG 21 2004

...STRONG THUNDERSTORMS WILL AFFECT YORK...LEBANON AND DAUPHIN
COUNTIES THROUGH 2 AM...

AT 110 AM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED
STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM 2 MILES WEST OF
LEBANON TO 3 MILES NORTH OF ELIZABETHTOWN TO 3 MILES SOUTHWEST OF
THREE MILE ISLAND...MOVING NORTHEAST AT 30 MPH. THE THUNDERSTORMS
WILL BE NEAR FREDERICKSBURG...LEBANON AROUND 120 AM...LAWN AROUND 135
AM...MOUNT GRETNA AROUND 140 AM...CORNWALL AND LEBANON AROUND 145 AM.

VERY HEAVY RAIN WILL FALL...AND WILL CAUSE WATER TO POND ON ROADS AND
QUICKLY FILL ROADSIDE DITCHES AND SMALL STREAMS.

WIND GUSTS TO 45 MPH ARE POSSIBLE WITH THESE STORMS. ALSO...EXPECT
INTENSE LIGHTNING. DO NOT SEEK SHELTER UNDER TREES OR STAY IN THE
OPEN WHEN LIGHTNING THREATENS.

JV