624
FXUS61 KCTP 011704
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
104 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 /18Z WEDNESDAY THROUGH MONDAY/
INTERMITTENT MVFR CEILINGS ARE POSSIBLE EARLY TODAY AS DIURNAL
MIXING REJUVENATES THE DAYTIME CUMULUS DECK WITHIN THIS
HOT/HUMID AIR MASS, PRIMARILY OUTSIDE OF THE LOWER SUSQUEHANNA
VALLEY (KMDT/KLNS) WHERE LOW-LEVEL MOISTURE IS LESS FAVORABLE
(RHS AROUND 60-80%). OTHERWISE, WESTERLY WINDS OF 5-10 KTS WITH
A FEW GUSTS TO 15 KTS ARE EXPECTED DURING THE DAY, WITH VFR
CUMULUS DECK IN THE AFTERNOON TRENDING TOWARDS MAINLY CLEAR
SKIES DURING THE EVENING AS RIDGING SETTLES IN. THUNDERSTORM
CHANCES REMAIN LOW (10-20% CHANCE) DESPITE THE HEAT & HUMIDITY
DUE TO MID-LEVEL SUBSIDENCE AND DRY AIR ALOFT (MEAN 700-300 MB
RH AROUND 20%), WITH CONVECTIVE ACTIVITY CONTINUING TO FAVOR
UPSTATE NY AND NEW ENGLAND.
FOR TONIGHT, WINDS WILL TREND LIGHT AND VARIABLE WITH MAINLY
CLEAR SKIES. PATCHY OVERNIGHT FOG MAY ONCE AGAIN DEVELOP GIVEN
THE HUMIDITY, THOUGH LARGELY RAIN-FREE CONDITIONS AND PLENTIFUL
SUNSHINE DURING THE DAYTIME WILL CONTINUE TO MITIGATE THE
OVERNIGHT FOG POTENTIAL.
OUTLOOK...
THU-SAT...PATCHY AM FOG; OTHERWISE VFR. HOT & HUMID WITH ISOLD
PM T-STORMS PSBL. HIGH DENSITY ALTITUDE CONCERNS POSSIBLE.
SUN...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...TEARE
CLIMATE...DANGELO/STEINBUGL
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