296
FXUS61 KCTP 180533
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
133 AM EDT SAT JUL 18 2026
WHAT HAS CHANGED
* SEVERE THUNDERSTORM RISK UPGRADE TO LEVEL 3/5 (ENHANCED) FOR
SATURDAY AFTERNOON THROUGH SATURDAY EVENING
KEY MESSAGES
1) WILDFIRE SMOKE WILL RESULT IN UNHEALTHY AIR QUALITY AND
REDUCED VISIBILITY TODAY AND INTO EARLY SATURDAY
2) SEVERE THUNDERSTORMS WITH DAMAGING WINDS AND HEAVY RAINFALL
ARE POSSIBLE SATURDAY AFTERNOON THROUGH SATURDAY EVENING
DISCUSSION
KEY MESSAGE 1: WILDFIRE SMOKE WILL RESULT IN UNHEALTHY AIR
QUALITY AND REDUCED VISIBILITY TODAY AND INTO EARLY SATURDAY
VISIBLE SATELLITE SHOWS MAIN SMOKE LAYER OVER THE SOUTHWEST
QUADRANT OF THE CWA THIS AFTERNOON. HIRES MODEL DATA SHOWS THIS
LAYER SLOWLY PIVOTING AND RETREATING TO THE NORTH/EAST LATE
TONIGHT THROUGH EARLY SATURDAY AS THE MEAN FLOW SHIFTS TO THE
SOUTHWEST. THE WORST/UNHEALTHIEST AIR QUALITY WILL IMPACT THE
AREA FROM THIS AFTERNOON THROUGH EARLY SATURDAY MORNING BEFORE
CONDITIONS IMPROVE BY SATURDAY AFTERNOON.
STATEWIDE CODE PURPLE AIR QUALITY ALERT FOR JULY 17TH
-------------------------------------------------------------
KEY MESSAGE 2: SEVERE THUNDERSTORMS WITH DAMAGING WINDS AND
HEAVY RAINFALL ARE POSSIBLE SATURDAY AFTERNOON THROUGH SATURDAY
EVENING
SPC UPGRADED MOST OF CENTRAL PA TO LEVEL 3/5 SEVERE T-STORM RISK
DRIVEN BY 45% DAMAGING WIND PROBABILITY.
AS THE SMOKE CLEARS, SCATTERED TO NUMEROUS THUNDERSTORMS ARE
FORECAST SATURDAY. THE LATEST MODEL PROJECTIONS SUPPORT AN
INCREASINGLY FAVORABLE SEVERE STORM ENVIRONMENT INCLUDING
STRENGTHENING DEEP LAYER WIND FIELDS AND RICH LOW LEVEL
MOISTURE. A REMNANT SURFACE FRONT INITIALLY DRAPED FROM SOUTHERN
NJ INTO WESTERN PA WILL LIFT NORTHEASTWARD AS AN EFFECTIVE WARM
FRONT, IN ADVANCE OF A COLD FRONT TRAILING LOW PRESSURE
TRACKING ACROSS SOUTHERN QUEBEC TOWARD NORTHERN MAINE.
THE DEPARTING/EXITING SMOKE LAYER WOULD BE HELPFUL IN ALLOWING
FOR STRONG DIURNAL HEATING AND MODERATE INSTABILITY. HOWEVER,
IT'S UNCLEAR HOW MUCH EARLY DAY, WARM ADVECTION/ELEVATED
CONVECTION AND ASSOCIATED CLOUD COVER WILL COMPLICATE FUTURE
CONVECTIVE ROUNDS DURING THE AFTERNOON AND EVENING HOURS. SHOULD
ADEQUATE CLEARING/HEATING OCCUR, STEEP LOW LEVEL LAPSE RATES ON
SOUNDING PROFILES WILL SUPPORT A RATHER FAVORABLE WIND DAMAGE
THREAT. IN ADDITION TO THE WIND-DAMAGE THREAT, SOME HAIL AND
TORNADO POTENTIAL MAY ALSO EVOLVE WITH ANY SUPERCELL
DEVELOPMENT, PARTICULARLY IN THE VICINITY OF THE WARM FRONT
GIVEN THE PRESENCE OF FAVORABLE EFFECTIVE SRH. THE SOUTHWARD
ADVANCING COLD FRONT SHOULD BE A CATALYST FOR SECOND OR THIRD
ROUND LATE DAY/EVENING STORMS WITH DUEL WIND/TORNADO THREAT
ESPECIALLY NEAR REMNANT OUTFLOW BOUNDARIES.
SOUTHWESTERLY LOW-LEVEL FLOW AHEAD OF THE FRONT WILL TRANSPORT
A HIGH PW (>2") AIRMASS INTO CPA. STRONG SYNOPTIC FORCING,
DRIVEN BY AN AMPLIFYING TROUGH OVER THE NORTHEAST AND FAVORABLE
UPPER JET DYNAMICS, AND DEEP WARM-CLOUD DEPTHS WILL SUPPORT THE
POTENTIAL FOR VERY HEAVY RAIN RATES TO PRODUCE ISOLATED FLASH
FLOODING CONCERNS. WPC HAS KEPT ALL OF CENTRAL PA IN A LEVEL 1/4
MRGL EXCESSIVE RAIN OUTLOOK FOR SAT PM. SOME CONSIDERATIONS
WERE DISCUSSED FOR POTENTIAL FLOOD WATCH WITH PHI/LWX, BUT
DECIDED TO HOLD OFF FOR NOW GIVEN FAIRLY PROGRESSIVE STORM
MOTIONS AND SOMEWHAT LOCALIZED SPATIAL FF RISK.
A DRYING TREND IS EXPECTED SUNDAY WITH NOTICEABLY LOWER
HUMIDITY ALLOWING FOR A PLEASANT DAY AND RELATIVELY COOL NIGHT.
HOWEVER, LATEST RRFS SHOWS SOME NEAR SFC SMOKE RETURNING TO CPA
FROM THE GREAT LAKES. THIS COULD RESULT IN REDUCED AIR QUALITY
AND HAZY SKY CONDITIONS.
ADDITIONAL BOUTS OF RAIN/T-STORMS ARE POSSIBLE INTO THE
WORKWEEK. THE NEXT SEVERE WX FOCUS WILL BE ON TUESDAY 7/21 WITH
SPC ALREADY HIGHLIGHTING A 15% PROB (EQUIVALENT TO SLGT RISK
LEVEL 2/5). FORCING FOR THIS MEDIUM RANGE SEVERE OUTLOOK APPEARS
FAIRLY ROBUST AND WOULD TAKE STOCK IN THIS RISK MANIFESTING AT
SHORTER RANGES.
TEMPERATURES WILL TREND NEAR TO SLIGHTLY BELOW HISTORICAL
AVERAGES THROUGH LATE WEEK INTO MONTH-END WITH SOME NOTICEABLY
COOLER NIGHTS POSSIBLE.
AVIATION /06Z SATURDAY THROUGH WEDNESDAY/
THERE WILL BE TWO MAJOR AREAS OF CONCERN FOR THE NEXT 24 HOURS.
THE FIRST WILL BE THE CONTINUED VISIBILITY RESTRICTIONS AT ALL
TERMINALS DUE TO HEAVY SURFACE SMOKE CONCENTRATIONS.
VISIBILITIES WILL CONTINUE TO REMAIN LESS THAN 6 MILES ACROSS
MOST OF THE COMMONWEALTH THROUGH THE EARLY MORNING HOURS.
ANTICIPATE WIDESPREAD IFR AND MVFR RESTRICTIONS UNTIL AFTER 16Z
SATURDAY. A SURFACE CENTER OF LOW PRESSURE IS EXPECTED TO MOVE
OVER THE MID- ATLANTIC REGION TODAY, AND THIS WILL USHER OUT THE
SMOKE THIS AFTERNOON WHILE ALSO BRINGING CONVECTION TO THE
REGION.
THE TIMING OF THIS CONVECTION REMAINS THE SECOND POINT OF
CONCERN. THE CONSENSUS THINKING IS THERE WILL BE TWO ROUNDS OF
STORMS TODAY. THE FIRST WILL COME THIS MORNING AS A CLUSTER OF
SHOWERS WILL DEVELOP ALONG THE LEADING MOISTURE EDGE AHEAD OF
THE FRONT (PWATS INCREASING TO 1.5"-2.0") AS MOISTURE FILTERS
IN AHEAD OF THE GREAT LAKES SYSTEM, WITH A FEW THUNDERSTORMS
BEING POSSIBLE AS THIS ACTIVITY PROGRESSES WEST TO EAST ACROSS
THE COMMONWEALTH. THIS ACTIVITY SHOULD LARGELY END FROM WEST TO
EAST BETWEEN 16 AND 18Z. THE SECOND ROUND OF STORMS WILL KICK
OFF LATER IN THE AFTERNOON WITH A MAIN LINE OF STORMS ALONG THE
FRONT DEVELOPING BETWEEN 20 AND 22Z. CONVECTION IS EXPECTED TO
EXIT THE SOUTHEASTERN TERMINALS OF KLNS AND KMDT BY 06Z SUNDAY.
THESE STORMS TODAY WILL BE STRONG TO SEVERE AND MAY PRODUCE
GUSTY WINDS, HEAVY RAIN, AND FLIGHT RESTRICTIONS.
OUTLOOK...
SUN...LINGERING -SHRA WITH RESTRICTIONS POSSIBLE EARLY (PRIMARILY
DRIVEN BY LOW CEILINGS), WITH VFR FAVORED OTHERWISE.
MON...MAINLY VFR.
TUE-WED...RESTRICTIONS POSSIBLE IN SHOWERS/T-STORMS WITH COLD
FROPA EXPECTED BETWEEN TUESDAY/WEDNESDAY.
CTP WATCHES/WARNINGS/ADVISORIES
NONE.
WHAT HAS CHANGED...STEINBUGL
KEY MESSAGES...STEINBUGL
DISCUSSION...STEINBUGL
AVIATION...BOWEN
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