913
FXUS61 KCTP 171809
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
209 PM EDT SUN MAY 17 2026
WHAT HAS CHANGED
* CONTINUE TO TREND AFTERNOON HIGHS BELOW NBM GUIDANCE DUE TO
KNOWN WARM BIAS
* CHANGED WORDING FOR SHOWERS/STORMS TODAY & MONDAY FROM
PROBABILITY (SLIGHT CHANCE) TO COVERAGE (ISOLATED)
KEY MESSAGES
1) HOTTEST TEMPERATURES OF THE YEAR SO FAR FORECAST THE NEXT
COUPLE OF DAYS WITH HIGHS PUSHING INTO THE 80S AND 90S.
2) A STRONG COLD FRONT TO BRING SHOWERS AND THUNDERSTORMS WITH
THE POTENTIAL FOR SEVERE WEATHER ON WEDNESDAY FOLLOWED BY
COLDER TEMPERATURES.
DISCUSSION
KEY MESSAGE 1: HOTTEST TEMPERATURES OF THE YEAR SO FAR FORECAST THE NEXT
COUPLE OF DAYS WITH HIGHS PUSHING INTO THE 80S AND 90S.
DAYTIME HIGH TEMPERATURES WILL BE STEADILY RISING TODAY THROUGH
EARLY IN THE UPCOMING WEEK. AN ANOMALOUS UPPER RIDGE
AMPLIFYING OVER THE EAST-CENTRAL U.S. WILL HELP TO CREATE VERY
WARM TO HOT, SUMMERLIKE CONDITIONS CENTERED ON MONDAY AND
TUESDAY. 500 MB HEIGHTS PER THE GEFS RISE ABOUT 120 DAM BETWEEN
SUNDAY MORNING AND LATE MONDAY WITH STANDARDIZED ANOMALIES OF
THESE HEIGHTS REACHING OVER +2 SIGMA ALONG THE MID ATLANTIC
COAST 18Z MONDAY THROUGH 18Z TUESDAY.
HIGH TEMPERATURES WILL PEAK IN THE MID 80S TO LOWER 90S MONDAY
AND TUESDAY AND COULD CHALLENGE DAILY RECORDS IN SOME LOCATIONS.
SEE THE CLIMATE SECTION FOR MORE DETAILS. MANUAL ADJUSTMENTS
WERE MADE TO LOWER NBM MAXT BY A FEW DEGREES DUE TO A KNOWN
SYSTEMATIC BIAS CORRECTION ISSUE IDENTIFIED DURING THE SHOULDER
SEASONS. THIS SHOULD ALSO KEEP MAX HEAT INDICES UNDER 100F,
PRECLUDING ANY NEED FOR HEAT ADVISORIES. STILL, HEAT RISK
IMPACTS WILL CONTINUE TO BE MONITORED GIVEN THE QUICK RAMP-UP IN
HEAT AND LIMITED ACCLIMATION TIME.
DEWPOINTS OVER 60F FOR MANY WILL ALSO FEEL QUITE HUMID RELATIVE
THE RECENT COOL STRETCH WE'VE HAD. WITH A BOUNDARY JUST TO OUR
NORTH AND SUFFICIENT INSTABILITY IN THE WARM SECTOR OVER PA,
THERE WILL BE A CHANCE FOR SOME STRAY AFTERNOON AND EARLY
EVENING SHOWERS OR THUNDERSTORMS MONDAY AND TUESDAY. MOST FOLKS
SHOULD STAY DRY, BUT THUNDERSTORMS COULD DROP A QUICK 0.10 TO
0.25" OF RAIN IN ANY ONE LOCATION.
-------------------------------------------------------------
KEY MESSAGE 2: A STRONG COLD FRONT TO BRING SHOWERS AND THUNDERSTORMS
WITH THE POTENTIAL FOR SEVERE WEATHER ON WEDNESDAY FOLLOWED BY
COLDER TEMPERATURES.
A COLD FRONT (ACCOMPANIED BY MORE WIDESPREAD AND FREQUENT
SHOWERS/T-STORMS) BRINGS RELIEF TO THE RELATIVELY SHORT BOUT OF
HEAT AND MODERATE HUMIDITY WEDNESDAY INTO THURSDAY. DOD MAX TEMP
DROP FROM TUESDAY TO WED WILL BE 20 DEG F OR GREATER IN MOST
LOCATIONS.
SOME OF THE AI GUIDANCE PAINTS AN ELEVATED RISK OF SEVERE
WEATHER ACROSS THE LOWER SUSQUEHANNA VALLEY ON WEDNESDAY
AFTERNOON IN THE PRESENCE OF PEAK HEATING AND SUFFICIENT
SHEAR/CAPE PROFILES. THE MAGNITUDE & LOCATION OF THE SEVERE
THREAT WILL BE HIGHLY DEPENDENT ON COLD FRONT PASSAGE TIMING AND
AMOUNT OF CLOUD COVER IN ADVANCE OF THE FRONTAL BOUNDARY. THE
EVENTUAL RISK AREA WILL HIGHLIGHT LOCATIONS ALONG AND DOWNSTREAM
OF THE COLD FRONT BETWEEN 12PM AND 8PM ON WEDNESDAY.
IN THE WAKE OF THE COLD FRONT, HIGH PRESSURE WILL BUILD IN FOR
A SHORT TIME. TEMPERATURES ARE FORECAST TO COOL DOWN BACK TO
HISTORICAL/CLIMO AVERAGES FOR LATE MAY FOR THE END OF NEXT WEEK.
EARLY INDICATIONS SHOW THE AFOREMENTIONED COLD FRONT STALLING
OUT SOUTH OF THE MASON-DIXON LINE LATE IN THE WEEK AND LIFTING
BACK NORTH ACROSS PA AS A WARM FRONT INTO MEMORIAL DAY WEEKEND.
THE CURRENT OUTLOOK FAVORS A COOLER/WETTER STRETCH THROUGH THE
HOLIDAY WEEKEND THANKS TO THAT WARM FRONT, BUT THERE IS STILL A
LOT OF TIME FOR THE FORECAST TO TREND IN A MORE
FAVORABLE/OPTIMISTIC DIRECTION FOR THE HOLIDAY WEEKEND THAT
MARKS THE UNOFFICIAL START OF SUMMER.
AVIATION /18Z SUNDAY THROUGH FRIDAY/
VFR WILL PREVAIL ON SUNDAY AS A RIDGE CONTINUES TO BUILD ALONG
THE EAST COAST ON THIS AFTERNOON. WITH THAT SAID, WEAK
SHORTWAVES EMBEDDED WITHIN THE NORTHERN PERIPHERY OF THIS RIDGE
MAY INITIATE SPOTTY CONVECTION. INSTABILITY WILL GROW SUPPORTIVE
OF CONVECTION AS THE DAY PROGRESSES, WITH HREF MEAN SBCAPE
AROUND 1000 J/KG & NEGLIGIBLE CIN IN PLACE, THOUGH SYNOPTIC-
SCALE SUPPRESSION WILL TEMPER ACTIVITY OVERALL. COVERAGE AND
TIMING OF CONVECTION IS INCONSISTENT ACROSS CAMS GIVEN THE
NEBULOUS FORCING, WITH SHOWER/THUNDERSTORM COVERAGE EXPECTED TO
BE BELOW 30% ACROSS THE REGION. ANY CELLS THAT DO DEVELOP WILL
DISSIPATE DURING THE EVENING AS DAYLIGHT ENDS AND RIDGING
BECOMES FURTHER ENTRENCHED ACROSS THE EAST COAST.
PATCHY FOG WILL BE POSSIBLE ONCE AGAIN SUNDAY NIGHT (MAINLY AFTER
06Z MONDAY) GIVEN LIGHT/VARIABLE WINDS, MAINLY CLEAR SKIES, AND
SURFACE DEW POINTS AROUND 60 DEGREES. CONFIDENCE IS TOO LOW
(<30%) IN FOG DEVELOPMENT FOR MENTIONS AT MOST SITES, BUT THE
POSSIBILITY REMAINS.
OUTLOOK...
MON-TUE...MAINLY VFR. PATCHY A.M. FOG. ISOLATED P.M. SHOWER OR
T-STORM POSSIBLE.
WED...RESTRICTIONS PROBABLE THROUGH WEDNESDAY NIGHT WITH
WIDESPREAD SHOWERS/STORMS ALONG CFROPA.
THU...LINGERING SHOWERS ACROSS S PA, RESTRICTIONS POSSIBLE.
CLIMATE
DAILY RECORD MAX TEMPERATURE FOR MAY 18-19:
5/18 5/19
HARRISBURG 94 IN 1962 95 IN 1962
WILLIAMSPORT 95 IN 1962 96 IN 1996
ALTOONA 91 IN 1962/1996/2017 92 IN 1996
BRADFORD 85 IN 1962 85 IN 1962
STATE COLLEGE 92 IN 1962 92 IN 1934/1996
OVERNIGHT LOW TEMPERATURES ON MONDAY NIGHT INTO TUESDAY ARE ALSO
IN JEOPARDY.
PLEASE NOTE: STATE COLLEGE CO-OPERATIVE OBSERVATIONS ARE A
24-HOUR SUMMARY TAKEN ONCE PER DAY AROUND 7 AM (7AM-7AM).
THEREFORE, A MAX TEMP OCCURRING IN THE DAYLIGHT OR LATE IN THE
DAY IS USUALLY REPORTED IN THE _NEXT_ DAY'S OBSERVATION. ALSO,
THE SAME MIN TEMP MAY BE REPORTED ON TWO CONSECUTIVE DAYS IF THE
MIN OCCURS AT OBSERVATION TIME.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
WHAT HAS CHANGED...BANGHOFF
KEY MESSAGES...LAMBERT/BANGHOFF
DISCUSSION...LAMBERT/BANGHOFF
AVIATION...BOWEN/TEARE
CLIMATE...DANGELO/STEINBUGL
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