Severe Thunderstorm Warning 141, NWS State College, PA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
245 PM EDT FRI JUN 16 2000

...SLOW MOVING FRONT AND JET ENTRANCE CIRCULATION TO BRING RAIN...

TWO BROKEN LINES OF THUNDERSTORMS ARE ATTEMPTING TO FORM ACROSS
CENTRAL PA THIS AFTERNOON.  WITH TEMPERATURES WELL INTO THE 80S OVER
MOST OF CENTRAL PA EXPECT CONVECTION TO CONTINUE WITH A CHANCE FOR
THUNDERSTORMS IN ALL ZONES EARLY THIS EVENING.  SOME THUNDERSTORMS
ARE FIRING ALONG THE LAKE BREEZE IN NORTHWESTERN PA.  LATER
TONIGHT...THE COLD FRONT PUSHING THROUGH IL/IN AND LINES OF SHOWERS
AHEAD OF IT WILL BRING ANOTHER CHANCE FOR THUNDERSTORMS OVERNIGHT IN
NORTHWESTERN SECTIONS.  THE BEST CHANCE OF THUNDER OVERNIGHT WILL BE
IN THE NORTHWESTERN COUNTIES.

THE COLD FRONT WILL STRUGGLE TO SAG SOUTHWARD ACROSS PA DURING THE
DAY SATURDAY.  IT WILL REMAIN QUITE WARM OVER THE SOUTH-CENTRAL AND
SOUTHEASTERN SECTIONS SATURDAY...WELL INTO THE 80S AGAIN.  IT SHOULD
BE COOLER IN THE NW WHERE THE MODELS SHOW THE FRONTAL BOUNDARY
SAGGING THROUGH EARLY IN THE DAY.  THE MESOSCALE MODELS SHOW
INSTABILITY SHOWERS LATE SATURDAY IN THE WARM AIR.  KEPT TEMPS IN
LOWER 70S NW TO MID  80S SE SATURDAY WITH HIGHER POPS MAINLY IN WARM
AIR AHEAD OF WEAKENING FRONT.

SATURDAY NIGHT...THE FRONT SHOULD CONTINUE TO SAG SOUTHWARD.  THE
MODEL SUGGESTS IT REACHES THE MD BORDER BY SUNDAY AM.  PROBABLY
UNDERDONE IN THE COARSER ETA.  THE LOW-LEVEL COOLER AIR SHOULD REACH
INTO NRN MD SUNDAY AM.  BY THAT TIME...THE FRONT WILL BECOME A MORE
E-W BOUNDARY...IN RESPONSE TO THE BROAD CONFLUENCE TO OUR NORTH AND
EAST ALOFT.

THE JET ENTRANCE CIRCULATION INCREASES DURING THE DAY
SUNDAY...CLOUDS SHOULD RAPIDLY MOVE FROM SW TO NE ACROSS THE
REGION.  RAIN SHOULD ARRIVE OVER THE SW AROUND MIDDAY AND LATE IN
THE EVENING IN THE NORTHEASTERN SECTIONS.  BUT LIKELY POPS ALONG
SOUTHERN TIER COUNTIES AND KEPT MOST LOCATIONS IN THE 70S REFLECTING
COLD AIR DAMMING...IN CASE THE FRONT SHOULD MOVE SLOWER...PUT LOWER
80S IN LOWER SUSQUEHANNA VALLEY.

THIS FRONTAL SURFACE SHOULD PROVIDE NICE LIFT INTO THE JET ENTRANCE
CIRCULATION SUNDAY NIGHT...EXPERIENCE SAYS IF THE AVN AND ETA ARE
CORRECT...THE FRONTAL BOUNDARY WILL SHARPEN OVERNIGHT AND WE COULD
SEE SOME ENHANCED RAINFALL OVERNIGHT SUNDAY INTO EARLY MONDAY.
ABOUT 90% OF THE NCEP ENSEMBLES SHOW THE MORE THAN 0.25 INCHES OF
RAINFALL OVERNIGHT SUNDAY INTO MONDAY.  A FEW MEMBERS SUGGEST THERE
COULD BE A HALF INCH OR MORE.  WILL MONITOR MOISTURE DEPARTURES IN
ETA SATURDAY AND SUNDAY TO SEE IF THIS COULD END UP A FAIRLY BIG
RAINFALL EVENT.

ENSEMBLES SHOW NEAR NORMAL TEMPS AT 850 MB AND POPS GENERALLY UNDER
30 PERCENT TUESDAY AND WED.  EXPECT NEAR NORMAL HIGHS AND LOWS
THROUGH MID WEEK.

WORK ZONES SENT AROUND 2 PM.

.CTP...NONE.

GRUMM