817
FXUS61 KPBZ 211715
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
115 PM EDT FRI AUG 21 2026
WHAT HAS CHANGED
THE FORECAST MESSAGING REMAINS GENERALLY UNCHANGED. THE AVIATION
DISCUSSION HAS BEEN UPDATED FOR THE 18Z TAF CYCLE.
KEY MESSAGES
1) A MARGINAL DAMAGING WIND AND HAIL THREAT MAY DEVELOP WITH
THUNDERSTORMS SATURDAY AFTERNOON/EVENING, FOLLOWED BY A COLD
FRONT THAT BRINGS PLEASANT WEATHER TO THE AREA EARLY NEXT WEEK.
DISCUSSION
KEY MESSAGE 1...
THE MAIN FOCUS REMAINS ON A SHORTWAVE THAT ACTS TO DEEPEN UPPER
TROUGHING OVER THE REGION SATURDAY INTO SUNDAY MORNING WHILE
DRIVING A COLD FRONT WEST TO EAST THROUGH THE REGION. HI-RES
ENSEMBLES ARE BEGINNING TO SUGGEST UPSTREAM CONVECTION TONIGHT
COULD RESULT IN SOME SORT OF DECAYING CONVECTIVE SYSTEM
ENTERING OUR EASTERN OHIO COUNTIES (ROUGHLY ALONG/WEST OF THE
I-77 CORRIDOR) EARLY TO MID SATURDAY MORNING. CONVECTIVE-
ALLOWING MODELS HAVE THAT FEATURE WEAKENING WITH TIME, BUT THEY
ALSO SUGGEST UPWARDS OF 1000-1500 J/KG MUCAPE ALREADY
DEVELOPING AHEAD OF IT, THANKS TO MOSTLY CLEAR SKIES AND A MID-
TO-LATE AUGUST SUN ANGLE. IT'S NOT UNCOMMON FOR CAMS TO WEAKEN
NOCTURNAL/MORNING CONVECTION TOO QUICKLY, ESPECIALLY IN THE
PRESENCE OF MARGINAL MUCAPE AND SHEAR. IF THAT ENDS UP THE CASE,
IT'S POSSIBLE THAT INSTEAD OF CONVECTIVE INITIATION WAITING
UNTIL LATE AFTERNOON AND EVENING HOURS, WE SEE AN OUTFLOW
BOUNDARY TRIGGERING THUNDERSTORM DEVELOPMENT DURING LATE MORNING
AND EARLY AFTERNOON AS IT TRACKS EASTWARD ACROSS THE NORTHERN
WV PANHANDLE AND INTO WESTERN PA.
ASSUMING THE MORNING CONVECTION DOES DECAY AS CAMS SUGGEST,
CONFIDENCE IS FAIRLY HIGH THAT BY MID TO LATE AFTERNOON THE
LOCAL STORM ENVIRONMENT COULD SEE UPWARDS OF 1500-2500 J/KG
CAPE, AROUND 850 J/KG DCAPE, AND 20-30 KNOTS OF DEEP-LAYER SHEAR
THAT WOULD BE CONDUCIVE TO LOCALIZED DOWNBURSTS AND PERHAPS
SOME WEAK ORGANIZATION INTO MULTICELL CLUSTERS, BOTH OF WHICH
SUPPORT A DAMAGING WIND THREAT. DRY AIR ALOFT WILL ALSO SUPPORT
A MARGINAL SEVERE HAIL THREAT, THOUGH SIGNIFICANT/GIANT HAIL
STILL APPEARS UNLIKELY.
THUNDERSTORM ACTIVITY SHOULD TAPER OFF AFTER DARK WITH THE LOSS
OF DAYTIME HEATING, FOLLOWED BY THE COLD FRONT MOVING THROUGH
AND EXITING THE AREA BY EARLY SUNDAY MORNING. COLD CORE
PROCESSES UNDERNEATH THE DEEPER TROUGH BEHIND THE COLD FRONT
WILL KEEP LAKE-ENHANCED SHOWER AND LOW PROBABILITY THUNDERSTORM
CHANCES IN THE FORECAST ON SUNDAY, WITH THE GREATEST FOCUS
ALONG THE RIDGES AND NORTH OF PITTSBURGH. THEREAFTER, DRY
WEATHER AND SEASONABLY COOL TEMPERATURES SETTLE IN THROUGH
MONDAY UNTIL BUILDING HIGH PRESSURE UNDERNEATH HEIGHT RISES
FOSTERS A WARMING TREND BACK TO NEAR-SEASONAL LEVELS TUESDAY.
AVIATION /18Z FRIDAY THROUGH WEDNESDAY/
VFR CONTINUES THIS AFTERNOON WITH A FEW OR SCT CU FIELD ACROSS THE
LOWLANDS THROUGH SUNSET. POPS ALONG THE EASTERN RIDGES HAVE BEEN ON
A DOWNWARD SWING AND THE CHANCE FOR ALL PORTS TO REMAIN DRY TODAY IS
RISING. LOCALIZED FOG, FAVORING RIVER VALLEYS, MAY DEVELOP AGAIN
SATURDAY MORNING WITH MODELS FAVORING AREAS SOUTH AND WEST OF
PITTSBURGH.
OUTLOOK... OTHERWISE, AN APPROACHING COLD FRONT AND UPPER TROUGH
PASSAGE FOSTERS SCATTERED TO LOCALLY NUMEROUS SHOWERS AND
THUNDERSTORMS THAT CROSS SATURDAY AFTERNOON INTO EARLY SUNDAY
MORNING. A FEW OF THESE STORMS SATURDAY AFTERNOON COULD BRING
DAMAGING WIND GUSTS. ADDITIONAL RAIN/RESTRICTION CHANCES LINGER
THROUGH SUNDAY EVENING THANKS TO COOLER NW FLOW AND LAKE MOISTURE
ENHANCEMENT.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
DISCUSSION...CERMAK/FRAZIER
AVIATION...FRAZIER/AK
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