222
FXUS61 KCTP 291806
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
206 PM EDT MON JUN 29 2026
WHAT HAS CHANGED
* HEAT ADVISORY FOR WARREN COUNTY NOON TUESDAY-10PM THURSDAY
KEY MESSAGES
1) SIGNIFICANT, LONG DURATION, AND DANGEROUS HEAT WAVE EXPECTED
FROM THE LAST DAY OF JUNE INTO INDEPENDENCE DAY/4TH OF JULY
HOLIDAY WEEKEND
DISCUSSION
KEY MESSAGE 1: SIGNIFICANT, LONG DURATION, 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 BE THE HEAT WAVE BEGINNING
TUESDAY (LAST DAY OF JUNE) INTO THE INDEPENDENCE DAY/4TH OF JULY
HOLIDAY WEEKEND.
FOR THE REST OF THE AFTERNOON, WE CAN'T RULE OUT A LOCALIZED,
TERRAIN INDUCED, SOUTHWARD DRIFTING RAIN SHOWER OR BRIEF
THUNDERSTORM OVER THE SOUTHERN POCONOS INTO THE SOUTH CENTRAL
ALLEGHENIES. A MAINLY CLEAR AND MUGGY OVERNIGHT PERIOD SHOULD
ALLOW FOR GOOD VIEWING OF THE STRAWBERRY MOON AND MAY ALSO
ALLOW FOR PATCHY FOG TOWARD DAYBREAK.
A VERY STRONG RIDGE BECOMING ANCHORED OVER THE EASTERN HALF OF
THE COUNTRY WILL SUPPORT A SIGNIFICANT, LONG DURATION, AND
DANGEROUS HEAT WAVE IMPACTING CENTRAL PA. MAX HEAT INDEX VALUES
BETWEEN 95 AND 110 DEGREES ARE FORECAST DURING THE AFTERNOON AND
EVENING TUESDAY THROUGH SUNDAY WITH WARM AND MUGGY CONDITIONS
OFFERING LITTLE TO NO OVERNIGHT RELIEF. THIS EQUATES TO
WIDESPREAD MAJOR TO EXTREME HEATRISK. WE INCREMENTALLY ISSUED A
HEAT ADVISORY FOR WARREN COUNTY WITH THE EXPECTATION OF FUTURE
EXPANSION OF HEAT HEADLINES TO EVENTUALLY COVER ALL OF CENTRAL
PA IN THE COMING SHIFTS.
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. SPC HAS SHIFTED THE LEVEL 1/5
MRGL RISK A BIT FARTHER TO THE NORTHEAST AND ESSENTIALLY OUT OF
THE FORECAST AREA/CWA FOR TUESDAY. HOWEVER, INHERENT UNCERTAINTY
IN THESE TYPES OF PATTERNS WILL KEEP LOWER RAIN/THUNDERSTORM
CHANCES IN THE FORECAST THROUGH THE WEEKEND.
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
HEAT ADVISORY FROM NOON TUESDAY TO 10 PM EDT THURSDAY FOR
PAZ004.
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...STEINBUGL
KEY MESSAGES...STEINBUGL
DISCUSSION...STEINBUGL
AVIATION...BOWEN
CLIMATE...STEINBUGL
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