Flash Flood Warning 64, NWS State College, PA

CENTRAL PENNSYLVANIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
235 PM EDT SUN APR 26 1998

...SUGGESTIONS...
TONIGHT...RAIN TURNING TO SNOW BEFORE ENDING EARLY EVENING NRN 1/3
PA. 1 TO 2 INCHES PSBL HIGHER TERRAIN. CNTRL 1/3 PA... RAIN ENDING
BY LATE EVENING... RAIN CUD MIX WITH SNOW OVER THE HIGHER TERRAIN
BEFORE ENDING. SRN 1/3 OF PA... RAIN CHC TSRA... ENDING OVRNGT. WUD
HV CLRG OR PARTIAL CLRG AFTER RAIN ENDS TONIGHT.
MONDAY... CHILLY... BEC MO CLDY NRN/WRN MTNS... CHC FLURRIES NRN
COUNTIES. BECMG PS OR PC SRN COUNTIES.
MONDAY NGT...CLRG.
TUE... MO SUNNY. PC MTNS.

...DISCUSSION...
A LOOP OF THE SFC STATION PLOTS ON AWIPS TELL THE WHOLE STORY ACRS
PA ERLY THIS AFTRN.... INCREASED NERLY SFC FLO IN NRN PA AND
INCREASING SWRLY FLO IN SW PA. THE FLO HAS BECOME INCREASINGLY
FRONTOGENETIC AND CONVRGNT IN RESPONSE TO THE APPRCH OF THE MID-WEST
SHRT WAVE. THIS IN EFFECT HAS SHARPLY INCREASING THE VERTICAL MOTION
OVR PA ORGANIZING THE PRECIP INTO A WIDE BAND WITH SOME +RA REPORTED
IN C-PA. AS A RESULT OF THE STRGER NRLY LL FLO... COLDER AIR HAS
SURGED INTO NRN PA TURNING SOME OF THE RAIN TO SNOW AT HIGHER
ELEVATIONS. WUDN/T BE SURPRISED TO SEE SOME ACC/S ABV 2000 FEET NOW.

THE MID-WEST SHRT WAVE WAS SUPPORTG THE INCREASED MOIST SWRLY FLO
INTO SW PA WHICH WAS ALSO FUELING THE PRECIP... AS IT ASCENDED OVR
THE SFC FRNT BNDRY DRAPED ACRS SW AND SC PA. PRECIP WAS DEFINITELY
ENHANCING AS IT WORKED INTO CNTRL AND ERN PA AS A RESULT. NOTE:
RAINFALL ESTIMATES FM THE KCCX 88D WERE SUSPECT DUE TO
BRIGHT-BANDING. SCTRD STORMS WERE BREAKING OUT OVR WRN OH IN
RESPONSE TO NR 60 DWPTS FEEDING INTO THE SFC BNDRY. DWPTS WERE UP TO
THE LOWER TO MID 50S IN SW PA... SO THINK SOME TSRA PSBL SRN PA INTO
THIS EVE. THINK THE FOCUS OF THE HEAVIER RAINS (NORTHEAST OF THE SFC
BNDRY) WILL SHIFT FM CNTRL PA INTO SRN PA THIS EVE AS A LARGE UPR
LVL PVOR LOBE ...ASSCTD WITH THE NRN BRANCH UPR TROF... SHIFTS
SEWRD. THIS UPR LVL TROF/PV LOBE WILL ALLOW THE LARGE COLD SFC HI OVR
CANADA TO BUILD S AND PRESS THE SFC BNDRY WELL S OF PA BY MONDAY AM.
LL CONV/FGEN WILL CONT ACRS SRN PA LATER IN THE EVE AS THE FRNTL
BNDRY PRESSES S AND CONTS TO BE OVERRUN BY A MOIST W-SW FLO. THE
AXIS OF MAXIMUM INSTABILITY IN THE SWRLY INFLO REGION REMAINS FAR
ENUF SW OF PA TO PRECLUDE EXCESSIVE RAINS TONIGHT IN SRN PA. LOOKING
FOR ANTHR .5  TO .7 INCHES OVR SRN PA BTWN 18Z TODAY AND 12Z
MONDAY.

HYDROLOGICALLY... THE JUNIATA BASIN IS NOW RESPONDING PRETTY WELL
WITH SHARP RISES... BUT ALL HEADWATER POINTS ARE WELL BLO FLOOD
STAGE. SMALL STREAMS ALSO RISING BUT NO MAJOR PROBLEMS YET. SOME OF
THE SMALLER TRIBS ALSO RESPONDING IN THE MAIN-STEM/W-BR SUS BASINS.
AS PER DSCNS W/ MARFC... THINK WE WILL GET AWAY WITH NO SIGNFT
FLOODING PROBLEMS... SO NO FLOOD WATCH. CNTRL PA NOW SEEING THE
BRUNT OF THE HEAVIER RAINS. THIS AREA OF RAIN SHUD SHIFT INTO SRN PA
LATER TODAY... WHERE RAINFALL HAS BEEN LIGHTER.

THE NRN BRANCH UPR LVL TROF SWINGS ACRS THE NERN U.S MONDAY. STRG LL
CAA CONTS THRU MONDAY ACRS PA. A SOLID SC DECK CURRENTLY SEEN OVR
SERN CANADA WILL ADVECT S AND AFFECT MUCH OF NRN AND WRN PA BY
MONDAY AFTERNOON. ETA 850 MB RH FIELDS HAVE A GOOD HNDL ON THE SC
DECK NOW. CANNOT RULE OUT A FLURRY OVR NRN PA MON PM... HECK IT/S
SNOWING NOW OVR THE HIGHER TERRAIN UP THERE

THE UPR LVL TROF PASSES BY MON NGT AND LEAVES A BIG... COLD CANADIAN
HIGH PRESSURE CENTERED OVR THE GREAT LAKES. THE SFC WINDS APPEAR TO
HOLD UP ALL NGT 5 TO 10 KTS... WHICH SHUD PRECLUDE WIDESPREAD FRST.
TEMPS AT IPT PROGGED TO HOLD ABV FREEZING AS WELL MON NGT. FOR
NOW... IT WUD BE PRUDENT TO HOLD OFF ON FREEZE WARNINGS FOR MON
NGT.

FOR TUE... HI PRES RDG FM SFC TO 300 MB BUILDS E INTO PA WITH ASSCTD
PATTERN OF SUBSC. 850 MB TEMPS COME UP SOME DUE TO THE SUBSDC AND LO
SFC DWPTS REMAIN TO LIMIT CU FORMATION.

NICOSIA