445
FXUS61 KCTP 300818
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
418 AM EDT TUE JUN 30 2026
WHAT HAS CHANGED
* CONFIDENCE IN A PROLONGED HEAT SPELL HAS INCREASED, AND HEAT
PRODUCTS HAVE BEEN ISSUED INTO SATURDAY FOR AFFECTED AREAS.
* BUMPED POPS UP FOR ISOLD-SCT SHRA/TSRA THIS PM AND WED PM
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
2) ISOLATED TO SCATTERED SHRA/TSRA POSSIBLE THIS AFTN/EVENING
AND AGAIN WED AFTN/EVENING.
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 ISSUE AND OVER-ARCHING MESSAGE IS THE EXCESSIVE HEAT
THROUGHOUT THE REMAINDER OF THE WEEK AND EVEN INTO THE 4TH. THE
BIG UPPER RIDGE OVER THE OH/TN VALLEYS WILL HEAVE EAST AND A
LITTLE NORTH THROUGH THE NEXT SEVERAL DAYS. ABUNDANT SUNSHINE
AND HIGH MOISTURE WILL BRING THE WORD /OPPRESSIVE/ BACK INTO
VOUGE FOR THE NEXT FEW DAYS WHEN TALKING ABOUT THE HEAT AND
HUMIDITY. AS WE HAVE BEEN MESSAGING FOR MANY DAYS, WE EXPECT A
SPELL OF 5 DAYS OF HEAT INDICIES OVER 100 FOR AT LEAST PART OF
THE CWA. THE PEAK OF THE HEAT AND HUMIDITY WILL BE WEDNESDAY AND
THURSDAY WITH NEARLY IDENTICAL HIS BOTH AFTERNOONS. MUCH OF THE
AREA WILL HAVE HEAT INDICIES BETWEEN 100 AND 110 THOSE TWO
DAYS. DUE TO THE HIGH CONFIDENCE IN THAT PART OF THE FORECAST,
WE HAVE ISSUED APPROPRIATE EXCESSIVE HEAT WARNINGS AND HEAT
ADVISORIES FOR THE NEXT FEW DAYS. THE HUMIDITY CREEPS INTO
WARREN CO TODAY, WHILE THE DEWPOINTS STAY IN THE 60S IN THE SE.
THE HEAT EXPANDS ON WED WITH TEMPERATURES NEARING 100 IN THE
URBAN AREAS OF EAST. WE'VE MADE VERY MINOR TWEAKS TO THE TEMPS
AND DEWPOINTS EACH DAY IN COLLABORATION WITH THE NEIGHBORS. THEY
WERE MAINLY TO NUDGE TS AND TDS DOWN FROM NBM JUST A HAIR. BUT,
IT KEEPS US RIGHT WHERE WE WERE 12 HRS AGO W.R.T. HEAT
INDICIES. THE HEAT WILL START TO ABATE FRI AND A LITTLE MORE
SAT. NOT MUCH, BUT LIKELY ENOUGH TO START TAPERING OFF THE
ADVYS/WARNINGS.
WE HAVE TRIED TO REFLECT THE TREND IN TEMPS LATER IN THE WEEK
IN THE TIMING OF EACH OF THE HAZARD SEGMENTS. NOTE: AFTER THE
FIRST PASS AT ISSUING THE HAZARDS/FLAGS, I REALIZED I HAD
FORGOTTEN TO HAVE MCKEAN CO IN WITH THE WIDE ADVY FOR THE BULK
OF THE ALLEGHENIES -- AND ALSO FORGOT TO KEEP THE ADVY FOR
BLAIR, BEDFORD AND FULTON COS INTO FRI. SO YOU MAY SEE TWEAKS
FROM THE FIRST ISSUANCES OF THE PRODUCTS - BUT, THEY ARE GOOD,
NOW.
AS WE HAVE BEEN ENCOURAGED TO DO, WE CHOSE TO USE THE LOW END
OF THE SCALE TO BASE THE WWAS. SO, WHILE ON THE FORECAST MAP,
>=50% OF CAMBRIA CO DOES NOT GET TO 100HI ANY DAY, WE FELT IT
WAS WISE TO INCLUDE THEM IN THE ADVY DUE TO JOHNSTOWN'S FEW
PIXELS THAT DO REACH 100. MANY OF THE PEOPLE MOST VULNERABLE TO
HEAT STRESS/ILLNESSES LIVE IN THE URBAN AREA OF THE CONEMAUGH
VALLEY. ALSO, WE CONSIDERED LEAVING MCKEAN AND POTTER COS OUT OF
THE HEAT ADVYS, BUT DECIDED TO INCLUDE THEM AS THERE WERE A FEW
PIXELS OF 100HI THERE, AND KEEPING IN MIND THAT NY STATE'S
THRESHOLD FOR ADVY IS ONLY 95 (PA IS 100). BUF AND BGM MAY YET
ISSUE ADVYS FOR THEIR OWN AREAS, AND THE RESULTING HOLE IN THE
NORTH-CENTRAL PA MTNS MAY LOOK ODD. TO HIT HOME THE MESSAGE
THAT IT WILL BE HOT AND HUMID (AND DANGEROUSLY SO IN MANY PLACES
FOR A FEW DAYS), WE FELT IT WAS NOT A BAD MOVE TO INCLUDE MCKEAN
AND POTTER. NOW, SOMERSET CO IS THE ODD MAN OUT FOR THIS GO
'ROUND. WE'VE LEFT THEM OUT OF THE ADVYS BECASUE THEIR HI
NUMBERS JUST WEREN'T CLOSE ENOUGH TO MAKE A STRONG CASE FOR
INCLUSION BASED ON FORECASTER JUDGEMENT/NUDGERS. THIS MATCHES
WITH PBZ AND LWX LEAVING THEIR HIGHEST-ELEVATION COS OUT OF THE
PRODUCTS - FOR NOW.
HEIGHT FALLS HAIL THE APPROACH OF A MINOR COLD FRONT WHICH
SHOULD ARRIVE ON FRIDAY OR SATURDAY. NATURAL FIREWORKS FOR THE
4TH. THE INCREASED CLOUD COVER AND SOME RAIN SHOULD HELP KNOCK
DOWN THE TEMPS, AND KNOCK OUT MOST WORRIES FOR HEAT PRODUCTS.
TEMPS IN THE SE HALF OF THE CWA WILL COME DOWN 3-5F FOR SAT
(FROM THE 100S OF FRIDAY). SO, IT WON'T BE A BIG CHANGE, BUT
PROBABLY ENOUGH TO DROP THE ADVYS FOR THE NW AND DOWNSHIFT THE
WARNING TO AN ADVY FOR THE SE HALF. SUNDAY SHOULD BE "COLD"
ENOUGH TO BE DONE WITH HEAT PRODUCTS.
-------------------------------------------------------
KEY MESSAGE 2: ISOLATED TO SCATTERED SHRA/TSRA POSSIBLE THIS
AFTN/EVENING AND AGAIN WED AFTN/EVENING.
CHANGES HAVE BEEN VERY MINOR WITH THE MAIN CHANGE NUDGING POPS
UP THIS AFTN/EVENING AND WED AFTN/EVENING WITH TWO SHORTWAVE
TROUGHS ROLLING OVER THE STRONG UPPER RIDGE AND NIPPING THE N
AND E WITH SOME FORCING. THIS FORCING, COMBINED WITH THE
HELP/LIFT OF THE CENTRAL PA RIDGES, SHOULD BE ENOUGH TO TRIGGER
A COUPLE OF SHRA/TSRA. SPC GENERAL THUNDER SUPPORTS THIS IDEA,
BUT MOST SHOULD BE N & E OF THE CWA. A WILD CARD WILL BE THE SE
THIRD OF THE AREA ON WED, WHERE CAPES GET SUPER HIGH AND THE
POSSIBLE DIP IN UPPER TEMPS MAY ALLOW ISOLD/SCT STORMS TO POP UP
THERE. IN COLLAB WITH PHI AND LWX, WE ADDED 20-30 POPS THERE FOR
WED PM.
AVIATION /07Z TUESDAY THROUGH SATURDAY/
VFR CONDITIONS ARE EXPECTED AT ALL TAF SITES THROUGH THE NIGHT
AS BROAD HIGH PRESSURE SITS OVER THE NORTHEASTERN US, WITH A FEW
PASSING HIGH CLOUDS AND LIGHT WINDS. SOME PATCHY OVERNIGHT
VALLEY FOG IS LIKELY TO FORM, ALBEIT LESS EXTENSIVE THAN IT HAS
BEEN THE PAST COUPLE OF NIGHTS, WITH ANY FOG FORECAST TO MIX
OUT BY 15Z TUESDAY. JST, AOO, UNV, AND IPT HAVE AROUND A 30
PERCENT CHANCE OF SEEING VISIBILITY DROP BELOW 6SM, AND CHANCES
ARE EVEN LOWER AT THE OTHER TAF SITES.
THE HIGH PRESSURE WILL SHIFT TOWARDS THE TENNESSEE VALLEY ON
TUESDAY, BRINGING SOUTHWEST WINDS OF 5-10 KTS WITH A FEW GUSTS
OF 15 TO 20 KNOTS POSSIBLE IN THE AFTERNOON. MOREOVER, A VFR
SCT-BKN CUMULUS DECK WILL DEVELOP DURING THE MORNING & EARLY
AFTERNOON HOURS, WITH A FEW AFTERNOON SHOWERS/THUNDERSTORMS
POSSIBLE ACROSS NORTHERN PA. HOWEVER, GUIDANCE CONTINUES TO
BRING HIGHER STORM CHANCES (>30% CHANCE) TOWARDS UPSTATE NY &
NEW ENGLAND WHERE LESS CAPPING IS IN PLACE, PRECLUDING TAF
MENTIONS OF SHOWERS/STORMS AT THIS TIME.
FOR TUESDAY NIGHT, VFR WILL CONTINUE TO PREVAIL WITH SCT-BKN
CUMULUS REMAINING OVERHEAD & FOG REMAINING UNLIKELY AT OUR TAF
SITES. A 20-30 KT LLJ (BELOW LLWS THRESHOLDS) WILL DEVELOP
DURING THE EVENING IN RESPONSE TO A TIGHTENING PRESSURE GRADIENT
ON THE PERIPHERY OF THE HIGH PRESSURE, WITH 925 MB WINDS
VEERING FROM SW TO W/WNW THROUGH THE NIGHT.
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 TODAY TO 8 PM EDT THURSDAY FOR PAZ004.
HEAT ADVISORY FROM NOON WEDNESDAY TO 8 PM EDT THURSDAY FOR
PAZ005-006-010>012-017-018-024-037-041-042.
EXTREME HEAT WARNING FROM NOON WEDNESDAY TO 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.
HEAT ADVISORY FROM NOON WEDNESDAY TO 8 PM EDT FRIDAY FOR
PAZ025-034-035.
WHAT HAS CHANGED...DANGELO
KEY MESSAGES...DANGELO
DISCUSSION...DANGELO
AVIATION...TEARE
CLIMATE...STEINBUGL
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