845
FXUS61 KCTP 021913
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
313 PM EDT THU JUL 2 2026
WHAT HAS CHANGED
DAY 2 SPC SLGT RISK AREA NOW COVERS ALL BUT A SMALL SLIVER OF
PA.
DAY 4 - 15% PROB OF SVR WEATHER WITHIN 25 MILES OF A LOCATION
EXTENDS INTO SOUTHERN ADAMS, YORK AND LANCASTER COUNTIES FROM A
FAIRLY LARGE AREA THAT COVERS MUCH OF THE DELMARVA, I-95
CORRIDOR IN VA AND MD AND THE BLUE RIDGE MTN REGION.
KEY MESSAGES
1) SIGNIFICANT, LONG DURATION, AND DANGEROUS HEAT WAVE WILL
PERSIST INTO INDEPENDENCE DAY.
2) A RATHER CONDITIONAL SEVERE WEATHER THREAT WILL EXIST FOR
FRIDAY AFTERNOON INTO SATURDAY NIGHT.
3) A LAZY FRONT OVER THE AREA WILL RESULT IN A MULTI-DAY THREAT
FOR THUNDERSTORMS. THIS COULD LEAD TO FLASH FLOODING OVER THE
WEEKEND AND INTO NEXT WEEK.
DISCUSSION
KEY MESSAGE 1: SIGNIFICANT, LONG DURATION, AND DANGEROUS HEAT
WAVE WILL PERSIST INTO INDEPENDENCE DAY.
WE WILL SEE ANOTHER FEW-SEVERAL DEG F OF WARMING THIS AFTERNOON,
ESPECIALLY THANKS TO FULL SUN AND ADIABATIC WARMING (ACROSS THE
CENTRAL RIDGE AND VALLEY REGION AND SUSQ VALLEY) AS A RESULT OF
THE DOWNSLOPING WESTERLY LLVL FLOW THAT'S CURRENTLY GUSTING
INTO THE MID AND UPPER TEENS (KTS).
EARLIER CU FIELD MIXED-OUT/DISSOLVED AS ANTICIPATED WITH CLEAR
SKIES AND SOME LIGHT HAZE OVER THE BULK OF THE CWA FOR THE REST
OF THE DAY.
EXTREME HEAT WARNINGS (CENTRAL CWA AND THE SUSQ VALLEY) AND
HEAT ADVISORIES (NORTHERN AND WESTERN MTNS OF PA) CONTINUE
THROUGH FRIDAY, THEN BECOME FOCUSED IN THE CENTRAL MTNS AND SUSQ
VALLEY AS HEIGHTS ALOFT/THICKNESSES FALL AND MAX TEMPS SLIP BY
A FEW DEGREES F.
-------------------------------------------------------
KEY MESSAGE 2: A RATHER CONDITIONAL SEVERE WEATHER THREAT WILL
EXIST FOR FRIDAY AFTERNOON INTO SATURDAY NIGHT.
WE WON'T HAVE ANY CHANCE FOR DEEP CONVECTION UNTIL LATER
TONIGHT (AT THE EARLIEST) WHEN A BIT OF UPPER FORCING ROLLS W-E
ON THE ZONAL FLOW JUST TO OUR N.
SINCE WE'LL STILL BE UNDER THE INFLUENCE OF THE STRONG UPPER
RIDGE, WE MAY NOT BECOME UNSTABLE ENOUGH AT NIGHT TO POP
THE VERY WARM MID LEVEL TEMPS UNLESS SOME SIGNIFICANT OUTFLOW
BOUNDARIES CAN BE DRIVEN SE INTO THE CWA FORM UPSTREAM TSRA/MCS.
SOME SHOWERS/STORMS MAY SLIDE IN FROM THE NW INTO THE NRN MTNS
OVERNIGHT, BUT THE BULK OF HI RES GUIDANCE SUGGESTS A VERY LOW
PROBABILITY ANYWHERE SOUTH OF THE NORTHERN TIER.
A LOT OF CAPE IS STILL EXPECTED ON FRIDAY DUE TO THE HEAT AND
HUMIDITY, AND THE CAP MAY GET WEAKER THROUGH THE DAY, ESP IN
THE NORTH AS THE RIDGE COULD GET SUPPRESSED TO THE SOUTH
SLIGHTLY.
SPC EXPANDED THE SLGT RISK TO COVER ALL OF PA FRIDAY (EXCEPT
FOR A SMALL SLIVER OVER FAR SW PA). PULSE SEVERE STORMS WITH
LOCALIZED DAMAGING DOWNBURST WINDS ARE THE PRIMARY THREAT
CONSIDERING VERY WARM TEMPS ALOFT AND WEAK TO MARGINAL DEEP
LAYER SHEAR.
MOST OF THE GUIDANCE KEEPS THE VAST MAJORITY OF THE AREA RAIN-
FREE FOR ALL OF THE DAY ON FRI AND BRINGS IN SOME CONVECTION
FROM THE WEST FRI NIGHT. THE HI-RES WRF MEMBERS OF THE HREF DO
MAKE MORE DAYTIME CONVECTION THAN THE OTHERS (SPECIFICALLY AFTER
19Z ACROSS THE NW/NCENT MTNS - APPARENTLY INITIATED BY THE LAKE
ERIE BREEZE).
SATURDAY LOOKS SIMILARLY MARGINAL/TENUOUS. THE BEST INSTABILITY
AND SHEAR WILL BE IN THE NRN MTNS IN THE AFTN SAT AND THEN IT
LOOKS BETTER FOR THE SRN HALF OF THE AREA SAT NIGHT.
-------------------------------------------------------
KEY MESSAGE 3: A LAZY FRONT OVER THE AREA WILL RESULT IN A
MULTI-DAY THREAT FOR THUNDERSTORMS. THIS COULD LEAD TO FLASH
FLOODING OVER THE WEEKEND AND INTO NEXT WEEK.
A SLOW-MOVING COLD FRONT COULD LANGUISH OVER OR VERY CLOSE TO
THE STATE OVER THE WEEKEND AND INTO EARLY NEXT WEEK. THE CWA
WILL BE IN THE WARM SECTOR SAT WHEN SCATTERED STRONG/SEVERE
STORMS WILL THREATEN. BUT, THE FRONT WILL THEN DIP INTO PA FROM
THE NORTH AND SHOULD BRING REPEATED BOUTS OF THUNDERSTORMS AND
HEAVY RAIN. THIS IS LOOKING VERY MUCH LIKE A TYPICAL MADDOX
FRONTAL HEAVY RAINFALL SCENARIO WITH THE FRONT DRAPED W-E AND
AMPLE MOISTURE FLOWING IN FROM THE S/SW. AN UPPER LOW MOVING
DOWN FROM THE UPPER GREAT LAKES IN THE FIRST TO MIDDLE PART OF
THE WEEK COULD FINALLY SHOVE THE FRONT FAR ENOUGH TO THE SOUTH
TO ALLEVIATE OUR WORRIES FOR FLOODING.
AVIATION /18Z THURSDAY THROUGH TUESDAY/
HIGH PRESSURE AT THE SURFACE AND ALOFT WILL CONTINUE TO BRING
THE ENTIRE REGION UNSEASONABLE HEAT AND HUMIDITY OVER THE NEXT
36-48 HOURS.
VFR WILL PREVAIL AT ALL LOCATIONS THROUGH THE FORECAST PERIOD.
WINDS WILL REMAIN GENERALLY LIGHT AND WESTERLY, THOUGH THE NEXT
SEVERAL HOURS (THROUGH 22Z) WILL SEE SOME GUSTS IN THE MID TO
UPPER TEENS ACROSS THE CENTRAL MTNS AND SUSQ VALLEY AIRFIELDS.
PATCHY VALLEY FOG IS EXPECTED AGAIN LATE TONIGHT ACROSS NORTHERN
PA.
BIGGEST CONCERN WILL BE DENSITY ALTITUDE OVER THE NEXT TWO
DAYS. IF YOU'RE FLYING ON THE HEAVY SIDE AND/OR TAKING OFF
FROM A RUNWAY ON THE SHORTER SIDE, DOUBLE CHECK THAT VALUE AND
ITS EFFECT ON YOUR PERFORMANCE.
OUTLOOK...
FRI-SAT...PATCHY AM FOG; OTHERWISE VFR. HOT & HUMID WITH PM
T-STORMS PSBL. HIGH DENSITY ALTITUDE CONCERNS POSSIBLE.
SUN...RESTRICTIONS POSSIBLE IN AFTERNOON T-STORMS.
MON...RESTRICTIONS POSSIBLE IN AFTERNOON T-STORMS.
CLIMATE
BRADFORD REACHED 89 DEGREES WED, BREAKING THE OLD RECORD OF 88
DEGREES SET IN 1963. HARRISBURG CAME UP ONE DEGREE SHORT OF
TYING THEIR OWN RECORD MAX WED.
TRIPLE DIGIT MAX TEMPS ARE FORECAST IN THE LOWER SUSQ VALLEY
(LSV) TODAY AND FRIDAY, AND 90S FOR SATURDAY.
THE LAST TIME HARRISBURG OBSERVED CONSECUTIVE DAYS WITH MAXT
GREATER THAN OR EQUAL TO 100F WAS BACK IN 2011 ON JULY 21-22.
THE RECORD NUMBER OF CONSECUTIVE DAYS WITH MAXT >= 100F IS 3
AND HAS OCCURRED 5 TIMES: (ALL IN THE MONTH OF JULY)
1999-07-16 TO 1999-07-18
1999-07-04 TO 1999-07-06
1991-07-19 TO 1991-07-21
1966-07-02 TO 1966-07-04
1936-07-09 TO 1936-07-11
THE LAST TIME HARRISBURG HIT THE CENTURY MARK WAS JULY 16TH IN
2024. PRIOR TO THAT, IT WAS JULY 19TH IN 2020.
HARRISBURG AVERAGES 1 DAY ANNUALLY WITH A MAXT >100F. THE MOST
NUMBER OF DAYS OBSERVED IN A YEAR IS 6 IN 1999.
THE RECORD MAXES FOR THE NEXT FEW DAYS ARE IN JEOPARDY:
STATION/DATE...07/02...07/03...07/04...07/05.
MDT.............104.....107.....104.....102..
IPT..............99.....100.....100.....100..
AOO..............97......97......97......94..
JST..............98.....100.....100.....101..
BFD..............90......91......91......91..
CTP WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY UNTIL 8 PM EDT FRIDAY FOR PAZ004>006-010>012-017-
018-024-033-037-041-042.
EXTREME HEAT WARNING UNTIL 8 PM EDT FRIDAY FOR PAZ019-025>028-
034>036-045-046-049>053-056-058-063.
HEAT ADVISORY FROM 8 PM FRIDAY TO 8 PM EDT SATURDAY FOR PAZ019-
026>028-036-045-046-049>053-056-058-063.
EXTREME HEAT WARNING UNTIL 8 PM EDT SATURDAY FOR PAZ057-059-
064>066.
WHAT HAS CHANGED...LAMBERT/DANGELO
KEY MESSAGES...LAMBERT/DANGELO
DISCUSSION...LAMBERT/DANGELO
AVIATION...LAMBERT/TEARE/TYBURSKI
CLIMATE...DANGELO/STEINBUGL/MARTIN
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