Severe Thunderstorm Warning 46, NWS State College, PA

CENTRAL PENNSYLVANIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
245 AM EDT SAT MAY 13 2000

SO FAR ALL IS QUIET ON OUR WESTERN FRONT. A COUPLE OF SHRAS SURVIVE
THE IMPRESSIVE CAP INTO THE ALLEGHENIES BUT CAN NOT PENETRATE ANY
FURTHER E JUST YET. THE CAP AT 00Z ON THE 13TH AT PBZ IS VERY
IMPRESSIVE. SFC TEMPS WOULD HAVE TO HEAT PAST 95F TO BREAK IT.

THE WARM FRONT REMAINS STALLED OVR THE SUSQ VAL RUNNING FROM DOV TO
MDT TO JUST W OF SEG AND IPT AND THEN NW TO BETWEEN BUF AND DUNKIRK.
DEWPTS ARE IN THE 64 TO 70F RANGE WEST OF THE FRONT AND IN THE 50S
OVR SE PA JUST E OF THE FRONT. 04 AND 05Z MESO SFC ANALYSIS SHOW THE
FRONT IS NOT MOVG. A SLITE SUBTLE PRES RISE IS OCCURING OVR THE
HUDSON VAL AND NEW ENG AND THIS MAY PUSH THE SHALLOW COOL AIR BACK
AS FAR AS SOUTH MTN B4 IT STOPS. THE WEAK SFC LOW NEAR BWI SUPPORTS
THIS IDEA AS WELL.

THE MESO ETA APPRS TO HAVE THE BEST SENSE OF WHAT IS HAPPENING NOW.
THE ONLY DISCREPENCIES ARE THE SFC LOW OVR MD IS ABOUT 100 MILES NW
OF WHERE IT ACTUALLY IS AND IT DID NOT RAIN A TENTH OF AN INCH IN NE
PA BETWEEN 3 AND 6Z.

THE MESO ETA IS ALSO HANDLING THE CONVECTION OVR THE OH VAL REALLY
WELL ATTM...EVEN SHOWING THE TEMPORARY WEAKENING TREND OVR MOST OF
OH. THIS WEAKENING MUST BE A FUNCTION OF THE LOSS OF HEATING AND THE
STRONG CAP THE CONVECTION IS RUNNING INTO. THERE IS ALSO A MIN IN
850 WINDS IN CENTRAL OH AS WELL.

BY 09Z THE MESO ETA INCREASES CONVECTION INTO CENTRAL OH BUT THE 850
WINDS REMAIN LIGHT. SO THIS INCREASE IN CONVECTION OVR OH MAY NOT
TAKE PLACE UNTIL LO LVL WINDS INCREASE AGAIN AROUND 12Z. BY THIS
TIME THE COLD FRONT IS MOVG INTO THIS REGION AND THE LIFT ASSOCIATED
WITH THE FRONT MAY BE ENUF TO PUSH CONVECTION UP THRU THE CAP. OUR
MM5 SHOWS A SIMILAR TREND WITH 3 HOUR RAINFALL TOTALS ALG THE FRONT
INCREASING QUITE DRAMATICALLY BETWEEN 12 AND 15Z OVR E OH AND NW PA.
THE MESO ETA BEING DRIER THAN THE MM5 MAY HAVE THE RIGHT IDEA WITH
OVERALL PRECIP AMTS...DUE TO THE MID LVL DRYING THAT IS FCST TO TAKE
PLACE DURG TODAY. AS MENTIONED BY MY PREDECESSOR THIS COULD MAKE
ANOTHER PRETTY GOOD HAIL DAY WITH JUST A FEW REPORTS OF WIND DAMAGE.
A LIMITING FACTOR FOR LARGE HAIL IS THE VERY HIGH FREEZING LEVEL AND
VERY HIGH -20C LEVEL. THIS SHUD LOWER AHEAD OF THE COLD FRONT AS CAA
IS FCST TO START ALOFT B4 THE SFC COLD FRONT GETS HERE.

AS THE COLD FRONT MARCHES ACROSS THE STATE IT WILL EVENTUALLY PINCH
OFF THE WARM SECTOR OVR CPA DURG THE AFTN. THE LOW OVR MD WILL
REMAIN THERE AND BECOME A TRIPLE POINT LOW. THE MM5 SHOWS THE BEST
LIS OVR NJ WHICH APPRS WRONG GIVEN THE E WIND OFF THE COLD OCEAN.
THE MESO ETA SHOWS THE LOWER SUSQ GETTING QUITE UNSTABLE ONCE AGAIN
BUT EVEN THIS MAY BE TOO FAR E WITH COOL MARINE AIR IN PLACE THIS
AM. IT WILL BE INTERESTING TO SEE IF THERE IS ENUF HEATING TO
COMPENSATE FOR THIS. IF I HAD TO GAMBLE ON JUST WHO HAD THE GREATEST
CHANCE FOR SEVERE WX IN PA TDY I WOULD HAVE TO SAY THE SHIPPENSBURG
AND CHAMBERSBURG AREA. THIS AREA WILL BE ON THE WARM SIDE OF SOUTH
MOUNTAIN (THE EAST SIDE WILL HAVE MARINE AIR THRU THE AM) AND THEY
WILL HAVE THE GREATEST LENGTH OF TIME TO HEAT B4 THE COLD FRONT
ARRIVES.

ONCE THE FRONT PASSES OUR WX WILL SETTLE DOWN. WE WILL BE BREEZY
BEHIND THE FRONT BUT NOT AS WINDY AS WE WERE BEHIND THE WED FRONT.
THE SFC LOW IS MUCH FURTHER N THIS TIME AND THEREFORE THERE IS AN
ANTI CYCLONIC CURVATURE TO THE ISOBARS. THIS REDUCES SFC CONVERGENCE
AND THE POTENTIAL FOR STRONG WINDS. THERE WERE AS MANY TREES DOWN
ACROSS OUR CWA WED EVE BEHIND THE FRONT AS THERE WERE IN THE TSRAS
EARLIER IN THE DAY. THAT SHUD NOT HAPPEN THIS TIME.

WHERE ANY ADJUSTMENTS TO THE FCST WILL BE MADE WILL BE IN MAX TEMPS
ON MOTHERS DAY. THE FAN FOR BFD SHOWS ONLY 50S FOR SUNDAY. THE
FWCBFD IS ONLY 59 SO A CHANGE NEEDS TO BE MADE.

IN THE EXTENDED...COLD UNSTABLE AIR WILL BE POURING SE OVR THE STATE
MON AND THIS MAY CAUSE A FEW SPKLES UP N. A MODERATING TREND WILL
DEVELOP TUE AND WED WITH LOW HUMIDITY. THE ECMWF BRING S THE NEXT
WARM FRONT IN WED NITE. WHILE THE MRF KEEPS IT OUT TIL THU.

.CTP...NONE SO FAR.

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PAZ004>006-010>012-017>019-024>028-033>037-041-042-045-046-049>053-
056>059-063>066-131500-

SEVERE WEATHER OUTLOOK
NATIONAL WEATHER SERVICE STATE COLLEGE PA
415 AM EDT SAT MAY 13 2000

...SLIGHT RISK OF SEVERE THUNDERSTORMS TODAY...

A STRONG COLD FRONT MOVING INTO OHIO EARLY THIS MORNING WILL MOVE
ACROSS CENTRAL PENNSYLVANIA THIS AFTERNOON. THUNDERSTORMS MAY
DEVELOP OVER AND JUST EAST OF THE ALLEGHENIES THIS AFTERNOON. ANY
STORMS THAT FORM WILL HAVE THE POTENTIAL OF PRODUCING DAMAGING WINDS
AND LARGE HAIL.

SKYWARN SPOTTER NETWORKS MAY NEED TO BE ACTIVATED LATER TODAY.

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