075
FXUS61 KCTP 190218
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
1018 PM EDT MON MAY 18 2026
WHAT HAS CHANGED
* DAY 2 SPC OUTLOOK UPGRADED TO A SLIGHT RISK (LEVEL 2 OUT OF
5) FOR DAMAGING WINDS IN NORTHWEST PA.
KEY MESSAGES
1) MORE HEAT & HUMIDITY WILL PRODUCE SCATTERED SHOWERS AND
THUNDERSTORMS ON TUESDAY AFTERNOON AND EVENING, SOME OF WHICH
COULD BE STRONG TO SEVERE, ESPECIALLY ACROSS NORTHERN PA.
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: MORE HEAT & HUMIDITY WILL PRODUCE SCATTERED
SHOWERS AND THUNDERSTORMS ON TUESDAY AFTERNOON AND EVENING, SOME
OF WHICH COULD BE STRONG TO SEVERE, ESPECIALLY ACROSS NORTHERN
PA.
BY TUESDAY, WE'LL STILL BE UNDER THE INFLUENCE OF THE
ANOMALOUSLY STRONG RIDGE OF HIGH PRESSURE, WITH BROAD
SOUTHWESTERLY FLOW CONTINUING TO PUMP WARMER TEMPERATURES AND
HUMID CONDITIONS INTO PENNSYLVANIA. HIGHS ON TUESDAY SHOULD BE
FAIRLY COMPARABLE TO TODAY, THOUGH AFTERNOON SHOWERS/STORMS IN
THE WEST COULD LIMIT HOW WARM IT GETS THERE.
AT THE SURFACE, A DEEPENING SURFACE LOW WILL LIFT ACROSS THE
GREAT LAKES WITH GRADUALLY SINKING HEIGHTS ALOFT IMPINGING
NORTHWEST PA. UNDERNEATH THIS SPRAWLING RIDGE, PENNSYLVANIA
WILL BE IN A MOIST AND UNSTABLE AIRMASS WITH MUCAPE VALUES
EXPECTED TO REACH 1000-1500J/KG. WITH MARGINAL BUT SUFFICIENT
SHEAR, THIS AMOUNT OF INSTABILITY COULD SUPPORT A FEW STRONGER
STORMS WILL STRONG TO DAMAGING WIND GUSTS. THE SPC UPGRADED NW
PA TO A SLIGHT RISK (LEVEL 2 OUT OF 5) OF SEVERE WEATHER TUESDAY
AFTERNOON. THE MARGINAL RISK EXTENDS DOWN TO ABOUT HALFWAY
BETWEEN I-80 AND I-76. LOW LEVEL HODOGRAPHS DO EXHIBIT SOME
SPIN AND AN ISOLATED TORNADO CANNOT BE RULED OUT IN NORTHWEST PA
CLOSER TO THE PARENT SURFACE LOW PRESSURE SYSTEM. CAMS DISAGREE
ON THE EXTENT TO WHICH CONVECTION INITIATION WILL OCCUR TUESDAY
AFTERNOON, BUT THE HEAT AND HUMIDITY WILL PROVIDE AS MUCH FUEL
FOR STORM DEVELOPMENT AS WE'VE SEEN YET THIS YEAR.
RAINFALL AMOUNTS ARE NOT EXPECTED TO BE ALL THAT IMPRESSIVE WITH
THIS SYSTEM, LARGELY OWING TO UNIMPRESSIVE/RELATIVELY DRY
MOISTURE PROFILES WITH DEWPOINTS IN THE UPPER 50S TO LOW 60S.
THE GOOD NEWS IS THAT THESE LOWER DEWPOINTS WILL KEEP OUR HEAT
INDEX VALUES BELOW 100F AND MITIGATE THE NEED FOR HEAT
ADVISORIES ACROSS THE AREA. RAINFALL AMOUNTS WILL BE HIGHEST
WEST OF I-99 AND LOCATIONS FARTHER EAST MAY NOT SEE MUCH RAIN AT
ALL BEFORE WEDNESDAY.
--------------------------------------------------------------
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. HIGH
TEMPERATURES ON WEDNESDAY IN NORTHWEST PA (BEHIND THE FRONT)
WILL BE NEARLY 20 DEGREES COOLER THAN MONDAY/TUESDAY. THE LOWER
SUSQUEHANNA VALLEY WILL SQUEAK OUT ANOTHER WARM DAY WITH HIGHS
IN THE UPPER TO 80S TO NEAR 90F.
AHEAD OF AND ALONG THE FRONT, THERE WILL BE A RISK FOR SEVERE
WEATHER AGAIN ON WEDNESDAY. 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. A MARGINAL RISK AREA COVERS LOCATIONS SOUTH AND EAST
OF THE I-80/I-99 CORRIDOR AND HIGHLIGHTS LOCATIONS ALONG AND
DOWNSTREAM OF THE COLD FRONT BETWEEN 12PM AND 8PM ON WEDNESDAY.
A FEW OF THE HI-RES MODELS DEPICT A SLOWER COLD FRONT PASSAGE.
SUCH A SOLUTION WOULD ALLOW FOR MORE DESTABILIZATION AHEAD OF
THE FRONT AND A HIGHER THREAT FOR DAMAGING STRAIGHT LINE WINDS.
IF THE FRONT ENDS UP BEING FASTER THAN PROGGED, CLOUDS/RAIN IN
THE MORNING COULD LIMIT INSTABILITY AND LEAD TO AN UNIMPRESSIVE
GUSTY SHOWER EVENT. REGARDLESS, THIS SYSTEM WILL FEATURE
BENEFICIAL RAINFALL WITH RAINFALL AMOUNTS GENERALLY 0.10-0.25"
AND LOCALLY HIGHER TOTALS POSSIBLE IN THUNDERSTORMS.
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 /01Z TUESDAY THROUGH SATURDAY/
EVENING CONVECTION THAT IMPACTED UNV AND IPT DISSIPATING AS OF
02Z. WITH A SHORTWAVE TROUGH TRACKING ACROSS THE GREAT LAKES
LATER TONIGHT INTO THE PREDAWN HOURS TUE, ADDITIONAL SHOWERS AND
STORMS MAY DEVELOP ACROSS WESTERN AND CENTRAL PA, BUT
CONFIDENCE IS LOW (20 PCT AT MOST AIRFIELDS, CLOSER TO 30 PCT AT
BFD AND JST). MARGINAL LLWS IS ALSO ANTICIPATED AS SFC WINDS
DIMINISH BUT WINDS AT 1500-2000 FT AGL INCREASE TO NEAR 35 KTS
FROM THE SW TO W.
AFTER 12-15Z TUE, SFC WINDS WILL PICK UP AGAIN WITH GUSTS UP TO
25KTS POSSIBLE. MUCH OF THE DAY WILL BE VFR. SCATTERED
SHRA/TSRA ARE POSSIBLE IN THE LATE AFTERNOON AND INTO TUE NIGHT,
PRIMARILY IN NW PA (INCLUDING BFD).
OUTLOOK...
WED...RESTRICTIONS PROBABLE THROUGH WEDNESDAY NIGHT WITH
WIDESPREAD SHOWERS/STORMS ALONG CFROPA.
THU...LINGERING SHOWERS ACROSS S PA, RESTRICTIONS POSSIBLE.
FRI...RESTRICTIONS LIKELY WITH RAIN MOVING IN FROM SOUTH TO
NORTH, LASTING INTO FRI NIGHT.
SAT...RESTRICTIONS LIKELY WITH RAIN.
CLIMATE
THE FOLLOWING CLIMATE SITES ACROSS CENTRAL PENNSYLVANIA SET NEW
DAILY HIGH TEMPERATURE RECORDS FOR MAY 18TH:
* A RECORD HIGH TEMPERATURE OF 92 DEGREES WAS SET IN ALTOONA,
BREAKING THE PREVIOUS RECORD OF 91 DEGREES INITIALLY SET BACK
IN 1962. THIS RECORD WAS TIED TWO TIMES PREVIOUSLY, BACK IN
1996 AND 2017.
* A RECORD HIGH TEMPERATURE OF 86 DEGREES WAS SET IN BRADFORD,
BREAKING THE PREVIOUS RECORD OF 85 DEGREES SET BACK IN 1962.
** NOTE: THE HIGH TEMPERATURE FOR STATE COLLEGE WILL BE REPORTED
AROUND 7AM ON 5/19. THIS IS DUE TO THE STATE COLLEGE CO-OP
OBSERVATIONS RUNNING 7AM-7AM. THUS, TODAY'S (5/18) HIGH
TEMPERATURE WILL BE REPORTED IN TOMORROW'S (5/19) OBSERVATION.
THIS RECORD, FOR REFERENCE, IS 92 DEGREES SET IN 1962.
---------------------------------------------
ABNORMALLY WARM TEMPERATURES WILL CONTINUE ON MAY 19TH, THUS
MULTIPLE SITES COULD CHALLENGE DAILY RECORD HIGH TEMPERATURES.
DAILY MAXIMUM HIGH TEMPERATURES FOR MAY 19TH:
* HARRISBURG: 95F SET IN 1962
* WILLIAMSPORT: 96F IN IN 1996
* ALTOONA: 92F SET IN 1996
* BRADFORD: 85F SET IN 1962
* STATE COLLEGE: 92F SET IN 1934, TIED IN 1996.
CTP WATCHES/WARNINGS/ADVISORIES
AIR QUALITY ALERT UNTIL MIDNIGHT EDT TONIGHT FOR PAZ057-059-
063-065-066.
WHAT HAS CHANGED...COLBERT
KEY MESSAGES...LAMBERT/BANGHOFF
DISCUSSION...LAMBERT/BANGHOFF
AVIATION...COLBERT/BOWEN
CLIMATE...BEATY
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