Severe Thunderstorm Warning 89, NWS State College, PA

CENTRAL PENNSYLVANIA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
230 PM EDT TUE JUL 15 1997

...ZONE SUGGESTIONS...
PHL...RECOMMEND 30 POP FOR SUSQ VAL FOR EVE.  WITH A 95 OVER 68 WED
SHD NOT VERIFY HEAT WARNING IN LWR SUSQ SO OK TO DROP FOR TOM.

PIT...THINK TEMPS WED TOO LOW E OF MTNS.  NEED UP 80S E OF MTS LOM
ON MTS.  THINK LWR SUSQ VAL NEEDS M90S WED.

...DISCUSSION...
CU FRMG RPDLY AS OF NOON LDT.  PIT SOUNDING IS QUITE UNSTABLE WITH
-4 LI 33 K INDEX.  MODIFIED SOUNDING GOES TO -6 LI AND 34 K INDEX.
MODIFIED CAPE VALUE IS 1933 J/KG.  MODEL SOUNDINGS SHOW CAPE VALUES
UP TO 2300J/KG OVR SUSQ VAL AT 0Z WED.  THERE ARE 2 FOCAL POINTS
FOR CONVECTIVE INITIATION AND THEY ARE THE USUAL LAKE BREEZE
CONVERGENCE AREA AND THE RIDGES FRM E WV INTO LAURELS AND S CENTRAL
MTNS OF PA.  CU LOOKS MUCH DIFFERENT THAN YDY.  YDY CU LOOKED
RAGGED WHILE TODAY CU HAS VERY WELL DEFINED TURRETS INDICATING LO
LVL CAP IS ALREADY BREAKING.  QUESTION MARK IS THE HIGHER LEVEL
INVERSION AROUND 500MB.  INITIAL SOUNDING SHOWS AN ISOTHERMAL LAYER
FROM 500MB UP TO ABOUT 475MB.  THERE APPRS TO BE ENUF ENERGY BELOW
THAT LEVEL TO POP PAST THIS BUT AS TIME GOES BY LOW LEVEL WINDS
BECOME DIVERGENT AND AFTER 0Z IT IS OVR FOR THE MTNS.

OVR THE SUSQ VAL THE WINDS ARE FEEBLE AT BEST IN LOW LEVELS BUT AT
LEAST THERE IS A PROPER PROFILE FOR CONVECTION THRU 6Z WED.  GIVEN
CAPE VALUES OVR 2000...LEE SIDE/THERMAL TROF OVR THE REGION UNTIL
6Z WED...AND CFROPA (FOR WHAT ITS WORTH) AROUND THE SAME TIME THERE
IS A DECENT SHOT AT CONVECTION OVER THE SUSQ VAL E THRU LANCASTER
AND SCHUYKILL COUNTIES AS WELL.  THE LIMITING FACTOR HERE IS HOW
MUCH HOT AIR WILL ADVECT E FROM THE ELEVATED HEATING SURFACES TO
THE WEST.  THIS CAN CAP CONVECTION AND KEEP CU TO JUST 1 TO 2
THOUSAND FEET THICK.  MY EXPERIENCE IN NEW MEXICO WAS THAT THIS IS
A VERY IMPORTANT FACTOR AND CAN EITHER DELAY OR STIFLE CONVECTION
ENTIRELY.

TRAJ SHOW AIRMASS FOR WED IS OVR OH AND IN TDY.  DEWPTS ARE 66 TO
69 DEGREES OVR THAT AREA.  FWC SHOWS NUMBERS STILL IN 90S FOR WED
SO PITZFP NEEDS TO BE BUMPED UP E OF MTNS.  WUD SUGGEST M 90S FOR
LWR SUSQ WED.  AGREE WITH PHL THAT COOLING AND DRYING WILL BE
SLOWER COMING IN.

WE HAVE TO WAIT FOR FRI NITE OR SAT FOR NEXT MEANINGFUL CFROPA.  SO
HEAT WAVE CONTINUES UNTIL THEN IN SUSQ VAL AND HOT SPOTS LIKE SO
VALS E OF MTNS.

PHL...THX FOR COORD.

HEAD
HEAD

PAZ028-035-036-045-046-049>053-056>059-063>066-160040-

SPECIAL WEATHER STATEMENT- EXCESSIVE HEAT WARNING
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1044 AM EDT TUE JUL 15 1997

...THE NATIONAL WEATHER SERVICE HAS CONTINUED THE EXCESSIVE
HEAT WARNING FOR SOUTHEAST PENNSYLVANIA THIS AFTERNOON...

THE EXCESSIVE HEAT WARNING INCLUDES THE FOLLOWING COUNTIES IN
THE LOWER SUSQUEHANNA VALLEY REGION...

DAUPHIN... LEBANON... CUMBERLAND... ADAMS... YORK... AND

LANCASTER.

...FORECAST DETAILS...

THE COMBINATION OF HIGH HEAT AND HUMIDITY THIS AFTERNOON WILL MAKE
FOR A DANGEROUS SITUATION OVER THE LOWER SUSQUEHANNA VALLEY REGION
IN PENNSYLVANIA. TEMPERATURES WILL SOAR TO BETWEEN 95 AND 100
DEGREES WITH RELATIVE HUMIDITIES UP TO 50 PERCENT. RECORD HIGH
TEMPERATURES ARE POSSIBLE IN HARRISBURG. THE OLD RECORD AT THE
MIDDLETOWN AIRPORT IS 99 DEGREES SET JUST TWO YEARS AGO IN 1995.
THIS RECORD COULD BE ECLIPSED THIS AFTERNOON.

AS A RESULT OF THE HEAT AND HUMIDITY...  HEAT INDICES WILL RANGE
FROM 105 TO 110 FOR A PERIOD THIS AFTERNOON IN THE WARNING AREA.
THE WORST CONDITIONS WILL OCCUR IN HIGHLY URBANIZED AREAS LIKE
HARRISBURG WHERE HEAT INDICES LIKELY WILL BE NEAR 110.

OVER THE MIDDLE SUSQUEHANNA AND WEST BRANCH VALLEYS AND PORTIONS OF
THE SOUTH CENTRAL MOUNTAINS... IT WILL BE A TAD COOLER THIS
AFTERNOON WITH SLIGHTLY LESS HUMIDITY. EXPECT TEMPERATURES TO REACH
THE MID 90S WITH HEAT INDICES OF 100 TO 105 DEGREES WHICH COULD BE
HAZARDOUS TO SOME INDIVIDUALS.

...WEATHER SYNOPSIS...

A LARGE... HOT HIGH PRESSURE SYSTEM STILL REMAINS IN CONTROL OF
PENNSYLVANIA/S WEATHER. THIS HIGH WILL SHIFT FURTHER SOUTH AND ALLOW
A WEAK COLD FRONT TO PUSH ACROSS THE REGION BY WEDNESDAY EVENING.
WEDNESDAY WILL ALSO BE HOT,,, BUT THE HUMIDITIES WILL BE LOWER THAN
TODAY. AFTER THE COLD FRONT IS EAST OF THE REGION... MORE TYPICAL
SUMMER WEATHER WILL BE IN PLACE ACROSS THE SUSQUEHANNA VALLEY AND
SOUTH CENTRAL MOUNTAINS WITH AFTERNOON HIGHS IN THE MID TO UPPER
80S INTO THE WEEKEND.

IN THE WARNING AREA...
THE HEAT AND HUMIDITY OF THIS MAGNITUDE WILL MAKE A DANGEROUS
COMBINATION FOR INDIVIDUALS IF PROPER PRECAUTIONS ARE NOT
TAKEN. IT IS IMPORTANT TO RESPECT THE HAZARDS OF PROLONGED
EXPOSURE TO HEAT AND HUMIDITY. EXCESSIVE HEAT KILLS PEOPLE BY
TAKEN THE HUMAN BODY BEYOND ITS ABILITIES TO COOL ITSELF. IN
A NORMAL YEAR...ABOUT 175 AMERICANS SUCCUMB TO THE DEMANDS
OF SUMMER HEAT.

AN EXCESSIVE HEAT WARNING IS ISSUED WHEN THE HEAT INDEX IS EXPECTED
TO EXCEED 105 DEGREES FOR MORE THAN 3 HOURS A DAY FOR TWO
CONSECUTIVE DAYS... OR WHEN THE HEAT INDEX IS EXPECTED TO EXCEED
115 DEGREES FOR ANY LENGTH OF TIME.

STAY TUNED TO NOAA WEATHER RADIO...YOUR LOCAL RADIO...TV OR
CABLE TV STATION FOR THE LATEST WEATHER INFORMATION.

OFFICIAL NATIONAL WEATHER SERVICE FORECASTS...STATEMENTS...
WATCHES...WARNINGS AND ADVISORIES FOR PENNSYLVANIA CAN BE FOUND
ON THE WORLD WIDE WEB AT THE FOLLOWING ADDRESS:
HTTP://IWIN.NWS.NOAA/GOV/IWIN/PA/PA.HTML
OR  140.90.6.254/IWIN/PA/PA.HTML

NICOSIA