070
FXUS61 KCTP 210009
AFDCTP
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE STATE COLLEGE PA
809 PM EDT MON JUL 20 2026
WHAT HAS CHANGED
* ENHANCED RISK AREA FOR SEVERE STORMS TUESDAY AFTERNOON AND
EVENING WAS EXPANDED TO COVER ALMOST ALL OF PA.
* THIN LAYER OF GENERALLY ELEVATED SMOKE WILL BE MAINLY OVER
WESTERN PA THROUGH LATE TODAY
KEY MESSAGES
1) SEVERE THUNDERSTORMS ARE A NEAR-CERTAINTY FOR TUESDAY
AFTERNOON AND EVENING. SOME AREAS OF FLASH FLOODING ARE ALSO
EXPECTED.
2) WILDFIRE SMOKE SHOULD STAY MAINLY OVER WESTERN PA, WITH
LEVELS BARELY NOTICEABLE IN THE EAST.
DISCUSSION
KEY MESSAGE 1: SEVERE THUNDERSTORMS ARE A NEAR-CERTAINTY FOR
TUESDAY AFTERNOON AND EVENING. SOME AREAS OF FLASH FLOODING ARE
ALSO EXPECTED.
FOR TONIGHT, PWAT VALUES WILL INCREASE FROM THE SOUTH BY 0.5 TO
0.75 OF AN INCH LEADING TO NOTABLY MORE HUMID LATE
NIGHT/TUESDAY.
SEVERE WEATHER IS ONCE AGAIN ON THE SLATE FOR TUESDAY AFTERNOON
AND EVENING AS AN AMPLIFYING UPPER LEVEL TROUGH HEADS SE ACROSS
THE GREAT LAKES REGION AND A STRONG, SUB-1000 MB SFC LOW (JUST
SOUTH OF JAMES BAY CANADA TUESDAY AFTERNOON) PUSHES A POTENT
COLD FRONT SE ACROSS PA LATE TUESDAY/EARLY WED.
TUESDAY (DAY 2) HAS BEEN CONSISTENTLY HIGHLIGHTED BY SPC FOR
MANY DAYS AS A POTENTIALLY ACTIVE AND DANGEROUS WEATHER DAY.
THE DY2 ENH RISK AREA HAS BEEN EXPANDED TO COVER THE ENTIRE
STATE OF PA EXCEPT FOR A SLIVER NEAR THE NY BORDER.
THE THREAT FOR POCKETS PF DAMAGING WIND IS NEAR CERTAIN, AND
COULD OCCUR ANYWHERE OVER THE CWA TUESDAY AFTERNOON AND EVENING.
ADDITIONALLY, THE THREAT FOR HAIL IS HIGHER THAN IT WAS THIS
PAST SATURDAY, AND THE POTENTIAL FOR TORNADOES IS SIMILAR, WITH
A MIX OF SUPERCELLS AND LINE SEGMENTS WITH MINI BOW ECHOES
EXPECTED TO BE THE PRIMARY STORM MODES GIVEN THE PRESENCE OF
LIKELY LOW LEVEL BOUNDARY FROM SOME MORNING CONVECTION ACROSS
THE EAST, FOLLOWED BY A SEVERAL HOUR PERIOD OF
SUBSIDENCE/PARTIAL CLEARING BENEATH AND JUICING UP OF THE
INSTABILITY AND DEEP LAYER SHEAR AS THE NOSE OF A 100+ KT 300 MB
JET APPROACHES FROM THE OHIO VALLEY LATE IN THE
AFTERNOON/EVENING.
0-1KM EHIS OF 2-3.5 M2/S2 WITH LEFTOVER LLVL OUTFLOW BOUNDARIES
AND ONE OR MORE PREFRONTAL/LEE-SIDE TROUGHS POINT TOWARD A
DISTINCT THREAT FOR SOME LONG-LASTING SUPERCELLS AND POTENTIALLY
A FEW TO SEVERAL EF1-2 TORNADOES ACROSS OUR CWA.
IT LOOKS LIKE A PRE-FRONTAL TROUGH WILL CHARGE IN FROM THE NW
AND CROSS THE CWA IN THE AFTERNOON HOURS. THE REAL COLD FRONT
WILL ARRIVE IN NW PA LATER IN THE EVENING/EARLY TUESDAY NIGHT.
IT MAY ARRIVE TOO LATE (SOME STABILIZATION COULD ALREADY HAPPEN)
AND HAVE LITTLE LEFT TO WORK WITH BY THE TIME IT GETS INTO THE
CWA TO MAKE MUCH OF A SEVERE THREAT.
THERE IS ALSO A THREAT FOR LOCALIZED FLASH FLOODING, BUT ONLY
IN PLACES THAT RECEIVE MULTIPLE ROUNDS OF HEAVY RAIN. THERE
SHOULD BE A FAIRLY FAST MOVEMENT TO THE STORM CELLS (ENE AT
ABOUT 40 KTS), LIMITING THE THREAT SOMEWHAT. HOWEVER, MOISTURE
IS EXPECTED TO BE VERY HIGH, PWATS 1.5-2".
---------------------------------------------------------
KEY MESSAGE 2: THICKER WILDFIRE SMOKE SHOULD STAY MAINLY OVER
WESTERN PA, WITH LEVELS BARELY NOTICEABLE IN THE EAST.
AN AIR QUALITY ALERT/ACTION DAY REMAINS IN EFFECT FOR MOST OF
SOUTHWESTERN PA WHERE LEVELS ARE EXPECTED TO BE UNHEALTHY FOR
SENSITIVE GROUPS. HRRR SMOKE PLUME PROGS KEEP THE THICKER SMOKE
OVER WESTERN PA WITH MUCH LESS OVER THE EAST. THE LIGHT WIND
THIS MORNING WILL TURN FROM EASTERLY TO SOUTHERLY THROUGH THE
DAY WHICH WILL HELP TO KEEP THE NEAR-SFC SMOKE FROM SPREADING
TO THE EAST.
AVIATION /00Z TUESDAY THROUGH SATURDAY/
GOOD VFR THIS EVENING WITH EITHER SKC OR FEW TO SCT AND LIGHT
WINDS. GET YOUR THREE NIGHT TAKEOFFS AND LANDINGS LATER THIS
EVENING WHILE THE GETTIN'S GOOD.
CEILINGS LOWER TO MVFR LATER TONIGHT IN ADVANCE OF A FRONTAL
BOUNDARY APPROACHING THE REGION. AN AREA OF -SHRA MAY SNEAK UP
INTO THE LOWER SUSQUEHANNA VALLEY (KMDT & KLNS) BY SUNRISE WITH
ABOUT A 40% CONFIDENCE.
WINDS ABOVE THE GENERALLY CALM SURFACE LAYER HAVE INCREASED TO
25-35 KTS AROUND 2,000 FT AGL, SO A MENTION OF LOW LEVEL WIND
SHEAR AT THE NORTHERN SITES WAS PLACED IN THE NEAR TERM
FORECAST. EXPECT THIS TO BECOME MOOT WHEN THOSE WINDS GET MIXED
TO THE SURFACE LATER TONIGHT AS THE FRONAL BOUNDARY GETS
CLOSER.
CONDITIONS WILL WAFFLE BETWEEN MVFR AND VFR THROUGH THE MORNING
AS -SHRA POP UP AHEAD OF THE MAIN AREA OF PRECIPTATION. THE
AREA HAS BEEN PLACED IN AN ENHANCED RISK FOR SEVERE STORMS
THROUGH THE AFTERNOON HOURS. HOWEVER, CONFIDENCE ON THE EXACT
TIME OF ANY STORM PASSING OVER AN INDIVIDUAL AIRPORT IS ONLY
ABOUT 20% AT THIS TIME. HENCE VCTS WAS ADDED FOR THE AFTERNOON
TIME FRAME WITH THE EXPECTATION THAT TIMING WILL BE NARROWED
DOWN AS WE MOVE CLOSER TO THE EVENT. IN ANY CASE, PLAN FOR +TSRA
TO DOT THE STATE THROUGH THE AFTERNOON INTO EVENING WITH THE
USUAL SUSPECTS OF WIND SHEAR, TURBULENCE, HEAVY RAIN, AND THE
POTENTIAL FOR HAIL (ESPECIALLY ALOFT WHERE IT HASN'T HAD TIME TO
MELT ON ITS WAY DOWN).
OUTLOOK...
WED...PERIODS OF LINGERING SHOWERS POSSIBLE WEDNESDAY MORNING AS
THE FRONTAL BOUNDARY EXITS THE STATE.
WED AFTERNOON-SAT...GOOD VFR CONDITIONS EXPECTED.
CTP WATCHES/WARNINGS/ADVISORIES
AIR QUALITY ALERT UNTIL MIDNIGHT EDT TONIGHT FOR PAZ024-033.
WHAT HAS CHANGED...LAMBERT/DANGELO
KEY MESSAGES...LAMBERT/DANGELO
DISCUSSION...LAMBERT/DANGELO
AVIATION...TYBURSKI
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