Flash Flood Warning 83, NWS State College, PA

CENTRAL PENNSYLVANIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
225 PM EDT WED JUN 19 1996

...LOW LEVEL BOUNDARY STUCK OVER PA MORE RAFL TO COME...

RADAR HAS STEADILY SHOWN A DECREASE IN ACTIVITY OVER THE REGION
OVER THE PAST 6 HOURS.  NEW ACTIVITY IS FIRING OVER OH/IN.  SOME
OF THIS ACTIVITY WILL MOVE INTO WRN PA TONIGHT.  THE BIG FORECAST
PROBLEM WILL BE LOCALLY HEAVY RAINFALL ALONG THE FRONTAL BNDRY.
IN ERN PA AND PARTS OF WRN PA.

THE MODELS ALL SEEM TO SHOW SUBSTANTIAL MID LEVEL DRYING OVER
MOST OF WESTERN AND NRN PA.  THIS SUGGESTS THAT RAINFALL AMOUNTS
WILL BE SIGNIFICANTLY LOWER THAN PREVIOUS NIGHTS OVER MUCH OF WRN
AND NRN PA...HOWEVER...CONVECTION OVER OH WILL LIKELY PROVE THIS
WRONG.   THE MODELS PLACE THE PCPN MAXIMA OVER NERN MOST PA OVER
THE NEXT 36 H.  BASED ON THE LL BNDRY THIS MAXIMA WILL LIKELY
OCCUR FARTHER SOUTH THAN GUIDANCE SUGGESTS.  AT 17Z THE FRONTAL
BNDRY EXTENDED FROM NEAR DCA TO AOO NWD PAST PIT INTO NERN OH AND
MI.  AS IT SLOWLY RETREATS NEWD...THE FOCUS OF HVY PCPN WILL
SHIFT NWED WITH IT.   TO COMPLICATE THINGS...A COASTAL FRONT LIKE
FEATURE WITH WARM MOIST ATL AIR HAS SET UP ALONG THE COAST FROM
THE DELMARVA...NJ...TO ERN LONG ISLAND.

THE THICKNESS FIELD IS DIVERGENT OVER WRN/WCNTRL PA TODAY AND
EARLY TONIGHT.  THIS SUGGESTS THAT AS THE TSTM ACTIVITY IN OH
MOVES OVER WRN PA IT WILL SLIDE S/SEWD ALONG THE LL
BNDRY...FOLLOWING AN ANTICYCLONIC PATH ACROSS THE STATE.  LOCALLY
HEAVY RAIN IS STILL A PROBLEM IN WRN PA...MAINLY NEAR THE BNDRY.

MODELS SUGGEST THAT THE SURGE OF WARM AIR OVER AHEAD OF A PSEUDO
COLD FRONT OVER OH WILL MOVE ACROSS CNTRL PA THUR.  SLIGHTLY
DRIER AIR WILL MOVE ACROSS THE REGION FROM WEST TO EAST THUR.
THE THREAT OF SHOWERS/TSTMS AHEAD OF THIS FEATURE WILL LINGER
THRU THURS AFTN IN CNTRL SECTIONS AND INTO THUR EVE IN EXTREME
ERN SECTIONS.

MODELS SUGGEST UPPER LEVEL CONV AS RIDGE BEGINS TO BUILD IN ALONG
WITH LL DIVERGENCE LATE THURS INTO FRI SUGGESTING PARTLY CLOUDY
SKIES AND A DECREASE IN THE POPS...LATE THUR INTO FRI.  CANT RULE
OUT SCT AFTN TSTMS AGAIN ON FRI.
GRUMM