Severe Thunderstorm Warning 165, NWS State College, PA

CENTRAL PENNSYLVANIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
225 PM EDT THU AUG 28 1997

...ZONE SUGGESTIONS...

...PHL...WUD CONFINE PRECIP THREAT IN FIRST PERIOD TO EVENING HOURS
AS MENTIONED IN THIS MORNING'S ZONES FOR LOWER SUSQ GROUPING...OR
"ENDING BY MIDNIGHT" WUD WORK.

...PIT...MAY NEED TO MENTION AN EVENING TRW OVER SERN-MOST PARTS OF
OUR CWA. OTHERWISE ALL ELSE LOOKS OK.

...DISCUSSION...
DRY AIR FILTERING DOWN ON NORTHWEST FLOW WHICH SEEMS TO BE
INTENSIFYING ON BACKSIDE OF DEVELOPING LEE TROF FEATURE OVER SUSQ
VALLEY. 03Z MESO ETA ACTUALLY PICKED UP ON THIS FEATURE AND
FORECAST A SIGNIFICANT AMOUNT OF LOW LEVEL NEGATIVE THETA-E
ADVECTION MOVING ACROSS WRN SECTIONS THRU THIS AFTERNOON.
CONVECTION FIRING OVER NRN TIER NOW SEEMS ASSOC WITH REMNANTS OF
WEST-EAST BOUNDARY WHICH PROGS SUGGESTED WUD FALL APART IN THE
SHEAR DEVELOPING AROUND ERN SYSTEM.

AREA IS DESTABILIZING SIGNIFICANTLY NOW UNDER STRONG AUG SUN WITH
DEWPOINTS OVER ERN SECTIONS STILL WELL UP INTO THE 60S. SATELLITE
SHOWS STORMS FIRING OFF OVER NRN PA WITH MOST OF THE REST OF THE
REGION REMAINING CAPPED. WATER VAPOR ALSO SHOWS SIG SHORTWAVE
DIVING SE OUT OF GR LAKES. PSU MESO DATA SHOWS CAPES INCREASING
BEST OVER SERN PA IN HIGHEST DEWPOINT AIR. THINK CONVECTION OVER
NRN TIER WILL SOON YIELD TO CONVECTION WANTING TO FIRE OVER MORE
FAVORED ERN LOCATIONS. INDICATED CONVECTIVE TEMPS THERE IN THE MID
80S SHOULD START TO BE REACHED WITHIN THE NEXT COUPLE OF HOURS. AS
UPPER SHORTWAVE NEARS REGION...I WUD EXPECT THIS TO BECOME THE MAIN
AREA OF INTEREST. WIND FIELDS ARE UNIDIRECTIONAL AND NOT TOO
IMPRESSIVE. MAIN SEVERE THREAT OUR PART OF THE WORLD WOULD SEEM TO
BE PULSE TYPE STRONG WINDS AS DRY AIR IN MID LEVELS ALLOW SOME
MEASURE OF EVAPORATIONAL COOLING. WET BULB ZERO HGHTS ARE FAIRLY
HIGH SO HAIL THREAT SEEMS LOW.

AFTER THIS AFTERNOON...SIGNIFICANTLY DRIER AIR WILL MOVE IN BEHIND
SYSTEM FOR THE OVERNIGHT AND FRIDAY. THIS SHUD MINIMIZE FOG THREAT
OVER MOST OF THE AREAS EXCEPT MAYBE WHERE ANY THUNDERSTORMS CAN
DUMP DECENT RAINS THIS EVE. EARLIER CONCERN WAS THAT COLD ADVECTION
AND LOW LEVEL MOISTURE WUD MAKE FOR A CLOUDY PERIOD BEHIND
FRONT...BUT IT NOW APPEARS I WAS BEING PESSIMISTIC. MODELS END UP
LIFTING UPPER TROF UP AND OUT VERY QUICKLY LEADING TO RAPID RETURN
TO FAIR WX. MED RANGE PROGS THEN HINT AT RETURN TO 3H WX WITH HGHTS
COMING WAY UP OVER ERN US OVER WEEKEND AND 1ST PART OF NEXT WEEK.
ECMWF HAS HUGE AREA OF 5900M 500MB HGHTS PARKED OVER ERN 2/3 US BY
TUES AM. AIR CONDITIONER WX LOOKS SET TO RETURN.
LA CORTE