431
FXUS61 KCTP 012343
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
743 PM EDT WED JUL 1 2026
WHAT HAS CHANGED
* BUMPED POPS UP FOR ISOLD-SCT SHRA/TSRA THIS PM IN THE NORTH/EAST
* EXPANDED THE HEAT ADVISORY INTO SOMERSET COUNTY FOR TODAY AND
THURSDAY
* EXPANDED THE EXTREME HEAT WARNING INTO BEDFORD, FULTON, AND
BLAIR COUNTIES FOR TODAY AND THURSDAY
KEY MESSAGES
1) SIGNIFICANT, LONG DURATION, AND DANGEROUS HEAT WAVE EXPECTED
FOR THE REST OF THE WEEK, AND INTO INDEPENDENCE DAY FOR THE
SOUTHEASTERN CITIES.
2) ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS TODAY, MAINLY
OVER THE NORTHEAST.
DISCUSSION
KEY MESSAGE 1: SIGNIFICANT, LONG DURATION, AND DANGEROUS HEAT
WAVE EXPECTED FOR THE REST OF THE WEEK, AND INTO INDEPENDENCE
DAY FOR THE SOUTHEASTERN CITIES.
SURFACE DEWPOINTS ARE REMAINING ELEVATED EVEN AS PEAK DAYTIME
HEATING BEGINS EARLY THIS AFTERNOON. DRIER AIR IS STRUGGLING TO
MIX DOWN TO THE SURFACE AND AS A RESULT HIGH HEAT INDEX VALUES
ARE BEING OBSERVED EVEN IN THE HIGHER TERRAIN. THIS HAS PROMPTED
THE EXPANSION OF THE BOTH THE HEAT ADVISORY AND EXTREME HEAT
WARNING FOR THIS AFTERNOON AND TOMORROW. THE MESSAGING WILL
REMAIN THE SAME OVER THE NEXT FEW DAYS FOR DANGEROUS HEAT
IMPACTING ALL OF CENTRAL PENNSYLVANIA.
THE BIG UPPER RIDGE AND THE SFC HIGH WILL BE IN PLACE FOR TODAY
AND THURSDAY. STARTING ON FRIDAY, THE UPPER RIDGE GETS A LITTLE
LESS-STRONG, AND THE SFC PRESSURE PATTERN GETS A LITTLE MUDDIED.
CLOUDS AND BETTER CHANCES FOR SHRA/TSRA WILL ENSUE. THAT SHOULD
HELP NUDGE TEMPS DOWN. WHILE WE WILL STILL BE IN A GENERAL
RIDGE, THE SFC PRESSURE DIPS A BIT AND A BAROCLINIC ZONE SLOWLY
DIPS IN FROM THE NORTH. BY SUNDAY, THE FLOW ALOFT IS ZONAL WITH
THE BAROCLINIC ZONE PARALLEL TO THE FLOW ALOFT (W-E) PROVIDING A
FOCUS SHRA/TSRA FOR THE END OF THE WEEKEND AND INTO NEXT WEEK.
TIME WILL TELL IF WE WILL BE UNDER THE GUN FOR ANY FLASH
FLOODING WORRIES SUN AND BEYOND.
-------------------------------------------------------
KEY MESSAGE 2: ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS
TODAY, MAINLY OVER THE NORTHEAST.
COOLING ALOFT HAS ALLOWED A FEW SHOWERS WITH EMBEDDED THUNDER
TO FORM OVER NY AND DROP INTO THE NORTHERN MTNS EARLY THIS
MORNING. THESE ARE WELL AWAY FROM THE SEVERE STORMS THAT
AFFECTED NORTHERN NY EARLIER IN THE NIGHT, BUT STILL CONNECTED
WITH THE SAME WEAK FORCING ALOFT. THERE IS A LITTLE CAPPING
INVERSION OVERHEAD THAT DISAPPEARS AROUND 9-10KFT AS TEMPS COOL
OFF RAPIDLY ABOVE THAT LEVEL, MORE SO IN THE NORTHEAST THAN THE
REST OF THE CWA. HOWEVER, THIS EARLY MORNING CONVECTION DOES
NOT HAVE THE EXTREME CAPE THAT ANY AFTERNOON/EVENING STORMS WILL
HAVE. THE HIGH HEAT AND HUMIDITY AND THE RELATIVELY COOL TEMPS
ABOVE THE CAP IN THE MID LEVELS WILL MEAN THAT ANY STORMS THAT
DO FORM LATER TODAY COULD MAKE VERY STRONG UP/DOWNDRAFTS AND
PRODUCE SOME ISOLATED SEVERE WIND GUSTS/DAMAGE. SPC DAY1 MRGL
RISK REMAINS UNCHANGED FROM WHERE THE DAY2 OUTLOOK HAD IT - OVER
THE NERN 5-6 COUNTIES. BREAKING THE CAP WILL BE NECESSARY TO
REALIZE THE 2000-3500J OF CAPE THAT ARE THERE FOR THE TAKING.
SEVERE 1"+ HAIL IS PROBABLY NOT A BIG ISSUE FOR US TODAY SINCE
IT IS SO WARM. BUT, THE WBZ IS ONLY 12KFT ALOFT. AS WE LOSE THE
DAYLIGHT, THE RISK FOR STORMS GOES DOWN QUICKLY. DID EXPAND THE
20+ POPS INTO LEBANON AND LANCASTER COS TO MATCH UP WITH LWX
AND PHI. BUT, THE CAP GETS STRONGER THE FARTHER SOUTH YOU GET IN
THE CWA AS THE 7H TEMPS WILL BE NEAR +12C AND THE 5H HEIGHTS
WILL BE AROUND 595DAM. OLD RULE OF THUMB THAT SAYS A 7H TEMP OF
+10C IS LIKELY TOO STRONG TO BREAK (OVER PA) ON MOST DAYS IS A
PRETTY GOOD RULE. HOWEVER, THE EXTREME HEAT WE WILL EXPERIENCE
TODAY COULD BLOW RIGHT THROUGH THAT WARM CAPPING LAYER ALOFT.
AVIATION /00Z THURSDAY THROUGH MONDAY/
HIGH PRESSURE AT THE SURFACE AND ALOFT WHICH IS DELIVERING
UNSEASONABLE HEAT AND HUMIDITY WILL EXPAND AND CENTER MORE
CLOSELY TO PENNSYLVANIA OVER THE NEXT 48 HOURS.
THIS WILL PUSH ANY RIDGE-EDGE CONVECTION FURTHER NORTH AND EAST
OF PENNSYLVANIA THURSDAY AND FRIDAY. GOOD VFR WILL PREVAIL AT
ALL LOCATIONS THROUGH THE FORECAST PERIOD. WINDS WILL REMAIN
GENERALLY LIGHT WITH JUST ISOLATED AREAS (20%) TOPPING 10 KNOTS
DURING THE AFTERNOON HOURS.
BIGGEST CONCERN WILL BE DENSITY ALTITUDE OVER THE NEXT TWO DAYS.
HIGH RESOLUTION SHORT TERM MODELS FORECAST DEWPOINTS TO DROP
OVERNIGHT AND THEN FALL INTO THE 50S DURING THE AFTERNOON
THURSDAY. THIS SHOULD KEEP ANY WIDESPREAD FOG FROM FORMING
OVERNIGHT (<10%), BUT WILL HELP SURFACE TEMPERATURES CLIMB A
FEW DEGREES HIGHER THAN TODAY. 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
TRIPLE DIGIT MAX TEMPS ARE FORECAST IN THE LOWER SUSQ VALLEY
(LSV) ON THURSDAY AND FRIDAY BOOKENDED BY UPPER 90S TODAY AND
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...07/01...07/02...07/03...07/04...07/05.
MDT.............100.....104.....107.....104.....102..
IPT.............102......99.....100.....100.....100..
AOO..............94......97......97......97......94..
JST..............98......98.....100.....100.....101..
BFD..............88......90......91......91......91..
CTP WATCHES/WARNINGS/ADVISORIES
HEAT ADVISORY UNTIL 8 PM EDT FRIDAY FOR PAZ004>006-010>012-017-
018-024-037-041-042.
EXTREME HEAT WARNING UNTIL 8 PM EDT FRIDAY FOR PAZ019-026>028-
036-045-046-049>053-056>059-063>066.
HEAT ADVISORY FROM 8 PM FRIDAY TO 8 PM EDT SATURDAY FOR PAZ019-
026>028-036-045-046-049>053-056>059-063>066.
EXTREME HEAT WARNING UNTIL 8 PM EDT THURSDAY FOR PAZ025-034-
035.
HEAT ADVISORY FROM 8 PM THURSDAY TO 8 PM EDT FRIDAY FOR PAZ025-
034-035.
HEAT ADVISORY UNTIL 8 PM EDT THURSDAY FOR PAZ033.
WHAT HAS CHANGED...DANGELO/BOWEN
KEY MESSAGES...DANGELO
DISCUSSION...DANGELO/BOWEN
AVIATION...
CLIMATE...DANGELO/STEINBUGL
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