Flash Flood Warning 87, NWS State College, PA

CENTRAL PENNSYLVANIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
215 AM EDT THU JUN 20 1996

TONIGHT IS MUCH QUIETER ACROSS THE CWA THAN LAST NIGHT.  HAVE
BEEN SOME PERSISTENT RW/S OVER YORK AND LANCASTER COS FOR THE
PAST HOUR OR TWO...BUT MAINLY 30 DBZ AND LESS ECHOS...AND THEY
ARE NOW SHOWING SIGNS OF WEAKENING AND MOVING OFF TO THE NE.  3
HR RAFL ESTIMATES OF LESS THAN 1/2 INCH IN THIS AREA.

OTHER THAN THAT...ONLY A FEW ISOLATED SHOWERS OVER THE CWA.
HEAVIER CELLS OVER CRAWFORD CO CURRENTLY AND FROM EARLIER TONIGHT
DISSIPATE BEFORE THEY MOVE EAST INTO WARREN CO.

ANOTHER TOUGH FORECASTING CHALLENGE TODAY.  PW/S REMAIN HIGH
THROUGH THE DAY... RUNNING FROM ABOUT 1.4 TO 1.6 INCHES.  UPPER
TROF AND ASSOCIATED SHORTWAVE ENERGY TO FINALLY SWING THROUGH
TODAY.  LI/S DROP PRETTY CONSIDERABLY TODAY ESP OVER SOUTHERN
TIER AS 500 TEMPS REMAIN IN THE -8/-9 RANGE.  MODEL LI/S OF -7
ACROSS SW PA... WHILE ONLY -2 ACROSS NE.  WITH NO GOOD UPPER FLOW
TO RUSH THINGS ALONG...THUNDERSTORMS AGAIN HAVE THE LIKELIHOOD OF
BEING SLOW MOVERS...CAPABLE OF TORRENTIAL DOWNPOURS.

THE QUESTION IS TRYING TO PINPOINT THE FAVORED LOCATIONS.  DOES
NOT SEEM TO BE ANY STRONG LOW LEVEL FOCUSING MECHANISMS TODAY...
BUT SUBTLE FEATURES EXIST.  NGM AND ETA SEEM TO HAVE A GOOD
HANDLE ON THE CURRENT CONVECTION AS DEPICTED IN THE SFC MOISTURE
CONVERGENCE FIELDS.  FOLLOWING THIS LEAD... SFC MSTR CONV WOULD
FAVOR NORTHERN PA OVER SOUTHERN PA FOR MORE WIDESPREAD ACTIVITY.
THIS COINCIDES MOST CLOSELY TO THE PROXIMITY OF THE SURFACE LOW
WHICH WILL TRACK NORTH OF CWA.  HOWEVER...THIS IS WHERE THE MOST
STABLE LOW LEVEL AIR REMAINS NORTH OF THE SURFACE FRONTAL
BOUNDARY.  ALSO...SOUTHERN PA HAS ALREADY HAD LOTS OF RAIN OVER
THE PAST TWO DAYS... AND IT WILL NOT TAKE TOO MUCH TO FLOOD HERE.

850 MSTR CONVERGENCE WOULD ALSO FAVOR NORTHERN PA IN GENERAL FOR
MOST WIDESPREAD FOR MOST OF THE DAY... BUT ETA PICKS UP ON
SIGNIFICANT BULLSEYE OVER LOWER SUSQUEHANNA REGION BY 00Z
TONIGHT.  ALTHOUGH NOT OUTLOOKED FOR SVR ATTM... WOULD NOT BE
SURPRISED FOR SOME SIGNIFICANT TRW/S LATER IN THE DAY ESP OVER
SOUTHEASTERN SECTIONS.

TO WRAP UP... FEEL IT IS TO TRICKY ATTM TO RULE OUT ANY SPECIFIC
AREA FROM WESTERN COUNTIES FLOOD WATCH.  AGREE WITH PIT COORD
CALL TO EXTEND WATCHES AND SEE EXACTLY WHAT AND WHERE THINGS
DEVELOP.  IN THE EAST... WOULD ALSO FEEL MORE COMFORTABLE WITH
FLASH FLOOD WATCHES CONTINUING FOR THE SAME AREA OF THE LOWER
SUSQ ALREADY OUT.  AS MENTIONED BEFORE... IT WILL NOT TAKE MUCH
TO FLOOD THIS REGION... AND MODELS ARE SUGGESTING THE POSSIBILITY
OF MORE RAIN THERE THIS AFT.  FOR THE REST OF THE PUBLIC
FORECASTS... WOULD FAVOR SOME TYPE OF TREND IN THE FORECAfST FOR
THE RAIN...SINCE MOST AREAS WILL LIKELY BE RAIN FREE THIS AM.

JUNG