712
FXUS61 KCTP 291713
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
113 PM EDT MON JUN 29 2026
WHAT HAS CHANGED
* ISSUED AN EXTREME HEAT WATCH FOR THE BULK OF THE CENTRAL RIDGE
AND VALLEY REGION OF PA ALONG WITH THE SUSQUEHANNA RIVER
VALLEY WHERE HEAT INDICES COULD PEAK BETWEEN 105 AND 110F WED-FRI
AFTERNOONS.
KEY MESSAGES
1) SIGNIFICANT, PROLONGED, AND DANGEROUS HEAT WAVE EXPECTED
FROM THE LAST DAY OF JUNE INTO INDEPENDENCE DAY/4TH OF JULY
HOLIDAY WEEKEND
DISCUSSION
KEY MESSAGE 1: SIGNIFICANT, PROLONGED, AND DANGEROUS HEAT WAVE
EXPECTED FROM THE LAST DAY OF JUNE INTO INDEPENDENCE DAY/4TH OF
JULY HOLIDAY WEEKEND
THE MAIN EVENT FOR THIS WEEK WILL UNDOUBTEDLY BE THE BUILDING
HEAT AND HUMIDITY WITH SOME RECORD HIGHS LIKELY BROKEN.
GEFS STANDARDIZED ANOMALIES SHOW A LARGE AREA OF +2-3 SIGMA 500
MB HEIGHTS BUILDING EAST AND ANCHORING ITSELF ACROSS PA FOR THE
WED-FRI PERIOD, BRINGING THE POTENTIAL FOR EXTREME HEAT WITH
APPARENT TEMPS OVER 105F EACH OF THE THREE AFTERNOONS. IT'S
PRETTY MUCH A SLAM DUNK FOR HEAT ADVISORY CONDITIONS ACROSS THE
CENTRAL RIDGE AND VALLEY REGION AND SUSQ VALLEY DURING THE MID
TO LATE WEEK.
AS THE PESKY QUASI-STNRY SFC FRONTAL BOUNDARY TO OUR SOUTH
MOVES NORTHEAST AS A WARM FRONT LATER TODAY INTO TUESDAY, HEAT
INDICES COULD SOAR TO NEAR 100F IN THE ALLEGHENY VALLEY OF
WARREN COUNTY TUESDAY, WHILE MOST OTHER ELEVATED AND FORESTED
AREAS OF THE COUNTY NOSE INTO THE 90S. THEY'LL BE ON THE CUSP OF
A POTENTIAL HEAT ADVISORY FOR TUESDAY. ELSEWHERE, A DECENT
AMOUNT OF SUNSHINE AND A DEVELOPING LIGHT SOUTHERLY FLOW WILL
BOOST AFTERNOON HIGHS INTO THE UPPER 80S AND LOW 90S, WITH HEAT
INDICES RANGING THROUGH THE 90S.
THE GREATEST FORECAST CHALLENGE (HIGHEST UNCERTAINTY/LOWEST
CONFIDENCE) CONTINUES TO CENTER AROUND RING OF FIRE CONVECTION
THAT COULD SPILL SOUTHEASTWARD AROUND THE NORTHERN PERIPHERY OF
THE UPPER RIDGE INTO THE AREA ON FRIDAY; HOWEVER, EC/GFS MODEL
GUIDANCE HAVE BOTH STARTED TO SHOW SOME PRECIPITATION MENTIONS
IN MORE RECENT MODEL GUIDANCE, SO THIS TIMEFRAME WILL BEAR
WATCHING AS WE GET CLOSER TO THE END OF THE WEEK.
---------------------------------------------------------------
AVIATION /18Z MONDAY THROUGH SATURDAY/
FAIR WEATHER CUMULUS CLOUDS ARE BEING OBSERVED ACROSS THE
COMMONWEALTH THIS AFTERNOON AS VFR IS EXPECTED TO PREVAIL ACROSS
ALL TAF SITES FOR THE NEXT 24 HOURS. HIGH PRESSURE IS BUILDING
IN OVER THE REGION AND DRY CONDITIONS WILL PERSIST FOR TODAY.
AFTERNOON THUNDERSTORM CHANCES WILL BE POSSIBLE LATER IN THE
WEEK, BUT GIVEN THE DOME OF HIGH PRESSURE IT WILL BE DIFFICULT
FOR STORMS TO BECOME WIDESPREAD. WHILE VFR IS MOST LIKELY TO
PREVAIL ACROSS MOST OF THE COMMONWEALTH FOR TONIGHT, PATCHY
OVERNIGHT FOG WILL ONCE AGAIN BE A CONSIDERATION (ALBEIT LESS
EXTENSIVE & PRIMARILY CONCENTRATED IN LOW-LYING AREAS VS. THIS
MORNING, GIVEN THAT YESTERDAY'S RAINFALL PRIMED US FOR FOG).
CONFIDENCE IN FOG FORMATION IS RELATIVELY LOW, BUT A FEW
MENTIONS OF BRIEF VISIBILITY REDUCTIONS HAVE BEEN MADE FOR THE
APPROPRIATE TAF SITES. WINDS WILL REMAIN CALM OUT OF THE ESE
FOR THE REMAINDER OF TODAY, BUT AS HIGH PRESSURE BUILDS IN FOR
TUESDAY EXPECT A WIND SHIFT TO THE SW WITH GUSTY WINDS POSSIBLE
DURING THE AFTERNOON ON TUESDAY.
OUTLOOK...
TUE-SAT...AM FOG; OTHERWISE VFR. TRENDING HOTTER WITH ISOLD PM
T-STORMS PSBL. HIGH DENSITY ALTITUDE CONCERNS POSSIBLE.
CLIMATE
TRIPLE DIGIT MAX TEMPS ARE FORECAST IN THE LOWER SUSQ VALLEY
(LSV) ON THURSDAY AND FRIDAY BOOKENDED BY UPPER 90S WEDNESDAY
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.
CTP WATCHES/WARNINGS/ADVISORIES
EXTREME HEAT WATCH FROM WEDNESDAY AFTERNOON THROUGH FRIDAY
EVENING FOR PAZ019-026>028-035-036-045-046-049>053-056>059-
063>066.
WHAT HAS CHANGED...LAMBERT/BEATY
KEY MESSAGES...LAMBERT/BEATY
DISCUSSION...LAMBERT/BEATY
AVIATION...BOWEN
CLIMATE...STEINBUGL
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