881
FXUS61 KCTP 181048
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
648 AM EDT MON MAY 18 2026
WHAT HAS CHANGED
* COLLABORATED WITH WFO LWX AND SPC TO INCREASED POPS FOR
PULSE/MULTICELL TSRA WITH THE POTENTIAL FOR GUSTY WINDS LATER
THIS AFTERNOON AND EVENING ACROSS SCENT PA AND THE WEST BR
SUSQ VALLEY. SPC PAINTED A MRGL RISK FOR SVR ACROSS THAT AREA
OF THE CWA.
* ALSO SLIGHTLY EXPANDED THE LOW POPS FOR SHRA/TSRA TUESDAY
AFTERNOON AND EVENING AND INCLUDED THE POTENTIAL FOR GUSTY
WIND AND HAIL.
KEY MESSAGES
1) HOTTEST TEMPERATURES OF THE YEAR SO FAR FORECAST THIS
AFTERNOON AND TUESDAY 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 THIS
AFTERNOON AND TUESDAY WITH HIGHS PUSHING INTO THE 80S AND 90S.
AN EXTENSIVE, BUT RATHER THIN VEIL OF HIGH CLOUDS COVERING MUCH
OF THE CWA EARLY TODAY WILL HELP TO CREATE NEAR OPTIMAL
CONDITIONS FOR A SURGE IN HEAT TODAY, THANKS IN PART TO THEIR
BLANKETING EFFECT TO REDUCE RADIATIONAL COOLING OVERNIGHT AND
THEIR MINIMAL IMPACT ON INSOLATION TODAY. TEMPS WILL START THE
DAYLIGHT HOURS IN THE 60S IN MOST LOCATIONS.
DAYTIME HIGH TEMPERATURES WILL BE STEADILY RISING TODAY THROUGH
TUESDAY AS AN ANOMALOUS UPPER LEVEL RIDGE AMPLIFIES OVER THE
EASTERN U.S. THIS WILL HELP TO CREATE VERY WARM TO HOT,
SUMMERLIKE CONDITIONS CENTERED ON THIS AFTERNOON AND TUESDAY
AFTERNOON.
500 MB HEIGHTS PER THE GEFS RISE ABOUT 120 DAM FROM SUNDAY
MORNING TO LATE MONDAY WITH STANDARDIZED ANOMALIES OF THESE
HEIGHTS REACHING OVER +2 SIGMA ALONG THE MID ATLANTIC COAST 18Z
MONDAY THROUGH 18Z TUESDAY.
COLLABORATED WITH LWX AND SPC TO PAINT A MRGL RISK FOR SVR TSRA
FROM THE SCENT MTNS TO THE WEST BRANCH VALLEY OF THE SUSQ NEAR
THE EASTERN EDGE OF SOMEWHAT STRONGER (35-40 KT) SWRLY MID LEVEL
WINDS WITH MU CAPE REACHING NEAR 2000 J/KG. ADDITIONALLY, THE
EASTERN EDGE OF AN ELEVATED MIXED LAYER (CURRENTLY OVER THE
MIDDLE OHIO RIVER VALLEY) WILL BE TRACKING ENE AT 15-20 KTS AND
REACH THE WESTERN EDGE OF THE MRGL RISK AREA AROUND 22-23Z TODAY
HELPING TO ENHANCE MID LEVEL LAPSE RATES AND UPDRAFT INTENSITY.
MENTIONED THE POTENTIAL FOR GUSTY WINDS ASSOCIATED WITH THE
THE CLEARLY HIGH-BASED CONVECTION OCCURRING WITHIN AN
INVERTED-V SOUNDING.
HIGH TEMPERATURES WILL PEAK IN THE MID 80S TO MID 90S THIS
AFTERNOON BASED ON ELEVATION AND PROXIMITY TO THE BEST LLVL
DOWNSLOPE AND ENHANCEMENT BY ADIABATIC WARMING VIA THE LIGHT
SOUTHWESTERLY BREEZE TODAY AND MODERATELY GUSTY WSW WIND ON
TUESDAY (WITH GUSTS IN THE 15 TO 20 MPH RANGE DURING THE LATE
MORNING AND AFTERNOON HOURS).
DAILY RECORD HIGHS COULD BE CHALLENGED IN SOME LOCATIONS. SEE
THE CLIMATE SECTION FOR MORE DETAILS. MANUAL ADJUSTMENTS WERE
MADE TO LOWER NBM MAXT BY A FEW DEGREES TODAY 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 MORE 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 ADDITIONAL
STRAY AFTERNOON AND EARLY EVENING SHOWERS OR THUNDERSTORMS
THIS AFTERNOON, WITH A BETTER CHANCE FOR LOCALLY ROBUST
CONVECTION ON TUESDAY ACROSS THE NORTHERN HALF OF PA. MOST
PLACES STAY DRY THOUGH, 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 AND
OPTIMISTIC DIRECTION FOR THE HOLIDAY WEEKEND THAT MARKS THE
UNOFFICIAL START OF SUMMER.
AVIATION /12Z MONDAY THROUGH FRIDAY/
PATCHY FOG/MIST WILL ERODE THIS MORNING AS SUNSHINE MIXES OUT
THE BOUNDARY LAYER, WITH VFR EXPECTED TO PREVAIL OUTSIDE OF
WHERE GUSTY SHOWERS/THUNDERSTORMS DEVELOP LATER THIS AFTERNOON
AND EVENING.
CONVECTIVE-ALLOWING MODELS (CAMS) ARE SIGNALING AT CONVECTIVE
INITIATION ACROSS THE MID-ATLANTIC LATER IN THE AFTERNOON VIA
LOW-LEVEL CONVERGENCE ASSOCIATED WITH A LEE TROUGH ACROSS THE
MID-ATLANTIC + UPPER-LEVEL SUPPORT IN THE RIGHT ENTRANCE REGION
OF A SUBTLE 40-KT JET STREAK. ALTHOUGH PRONOUNCED RIDGING ACROSS
THE EAST COAST WILL TEND TO SUPPRESS CONVECTIVE ACTIVITY, A FEW
SHOWERS/THUNDERSTORMS CANNOT BE RULED OUT. GIVEN THE MODERATELY
UNSTABLE ENVIRONMENT (HREF MEAN SBCAPE AROUND 1500-2000 J/KG),
INVERTED-V PROFILES IN PLACE (SURFACE T/TD SPREADS AROUND 15C
WITH DCAPE VALUES IN EXCESS OF 1000 J/KG), AND LOW-MODERATE WIND
SHEAR (AROUND 30 KTS) PRIMARILY WITHIN THE LOWEST 3 KM,
OUTFLOW- DOMINANT CELL CLUSTERS WITH LOCALLY GUSTY WINDS ARE THE
FAVORED STORM MODE. GIVEN THE WEAK FORCING MECHANISMS IN PLACE
+ STORM COVERAGE UNCERTAINTIES, MENTIONS WERE LIMITED TO PROB30
GROUPS AT THIS TIME. ACTIVITY IS EXPECTED TO DIMINISH AFTER
SUNSET AS FORCING WEAKENS DUE TO LOSS OF DAYTIME HEATING.
OTHERWISE, VFR IS EXPECTED TO PREVAIL OUTSIDE OF CONVECTION.
OVERNIGHT, A SHORTWAVE TRACKING ACROSS THE GREAT LAKES MAY
RESULT IN A FEW SHOWERS/THUNDERSHOWERS ACROSS WEST-CENTRAL PA
(MAINLY KBFD), THOUGH FLIGHT RESTRICTIONS APPEAR UNLIKELY WITH
THIS ACTIVITY.
OUTLOOK...
TUE...MAINLY VFR. PATCHY A.M. FOG POSSIBLE. 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.
FRI...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...LAMBERT/BANGHOFF/MARTIN
KEY MESSAGES...LAMBERT/BANGHOFF/MARTIN
DISCUSSION...LAMBERT/BANGHOFF/MARTIN
AVIATION...TEARE
CLIMATE...DANGELO/STEINBUGL
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