559
FXUS61 KPBZ 181653
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
1253 PM EDT TUE AUG 18 2026
WHAT HAS CHANGED
MONITORING THE POTENTIAL FOR FLOODING LATE WEDNESDAY INTO EARLY
THURSDAY SOUTH OF PITTSBURGH, PA.
KEY MESSAGES
1) NEW DISTURBANCE LATE TOMORROW INTO EARLY THURSDAY COULD
RETURN HEAVY RAIN POTENTIAL FOR PORTIONS OF THE REGION
2) RAIN AND THUNDERSTORM CHANCES RETURN SATURDAY INTO SUNDAY
WITH A PASSING TROUGH
DISCUSSION
KEY MESSAGE 1...
EXPECT SHOWERS AND THUNDERSTORMS TO RETURN FROM LATE TOMORROW
AFTERNOON INTO EARLY THURSDAY MORNING AS A TROUGH DEVELOPS OVER
THE GREAT LAKES AND OHIO RIVER VALLEY. WITH A ZONAL WESTERLY
FLOW IN PLACE ALOFT, DEVELOPMENT WILL DEPEND LARGELY ON WHETHER
MESOSCALE CONVECTIVE SYSTEMS (MCSS) OR THEIR REMNANTS TRACK INTO
THE REGION FROM THE WEST.
THE MAIN RISK TOMORROW EVENING INTO EARLY THURSDAY WITH STORM
AND SHOWER DEVELOPMENT IS FLOODING DUE TO TRAINING. A NUMBER OF
HIGH-RESOLUTION MODELS INDICATE AREAS SOUTH OF PITTSBURGH WOULD
BE VULNERABLE TO EXCESSIVE RAINFALL AMOUNTS (OVER 1 INCH). HREF
AND REFS DEPICTS 10-25% CHANCE OF RAINFALL AMOUNTS EXCEEDING
FLASH FLOOD GUIDANCE IN 6 HOURS SOUTH OF I-70 WEDNESDAY NIGHT.
THE BEST CHANCE FOR HEAVIER RAINFALL RATES ARE EXPECTED AFTER
7PM AS THE LOW-LEVEL JET INTENSIFIES FROM THE SOUTHWEST OVER
THE OHIO RIVER VALLEY.
THE POTENTIAL OF HEAVY RAINFALL DECREASES BETWEEN 5AM AND 8AM
THURSDAY MORNING AS THE TROUGH AXIS SHIFTS EAST INTO CENTRAL
PENNSYLVANIA. DRIER AND QUIET WEATHER IS EXPECTED LATE THURSDAY
AFTERNOON INTO FRIDAY.
KEY MESSAGE 2...
AS A RIDGE BUILDS OVER THE CENTRAL U.S. LATER THIS WEEK,
CONDITIONS FAVOR THE DEVELOPMENT OF A TROUGH OVER TH GREAT LAKES
AND OHIO RIVER VALLEY. THIS SETUP IS EXPECTED TO BRING SHOWERS
AND STORMS TO THE AREA FROM SATURDAY INTO SUNDAY. WHILE
MACHINE-LEARNING MODELS SUGGEST THE POSSIBILITY OF STRONG TO
SEVERE STORMS, FORECASTED UPPER-LEVEL SHEAR NOTES LESS THAN
30KTS-REMAINS TOO WEAK TO SUPPORT ORGANIZED CONVECTION.
DEPENDING ON THE AVAILABILITY OF MID-LEVEL DRY AIR, THE BEST
POTENTIAL COULD BE A BRIEF PERIOD OF STRONG DOWNDRAFTS SOUTH OF
PITTSBURGH WITH NOTED DCAPE VALUES OF 700J/KG TO 900J/KG.
AVIATION /15Z TUESDAY THROUGH SATURDAY/
IN MONDAY'S POST-FRONTAL ENVIRONMENT, A SIGNIFICANT AREA OF
BROKEN/OVERCAST STRATUS AROUND 5-6 KFT HAS DEVELOPED OVER MUCH
OF EASTERN OH, SOUTHWESTERN PA, AND NORTHERN WV. THIS HAS, AND
WILL CONTINUE TO, PRECLUDE FOG DEVELOPMENT AT THOSE SITES
THROUGH THE REMAINDER OF THE EARLY MORNING HOURS. ELSEWHERE
FARTHER NORTH, WHERE STRATUS DID NOT DEVELOP, FOG HAS SETTLED IN
AND DETERIORATED CONDITIONS AT FKL/DUJ TO PREVAILING IFR AND
BOUNCING DOWN TO LIFR AT TIMES. THIS WILL PERSIST FOR AN HOUR OR
TWO AFTER SUNRISE BEFORE HEATING AND MIXING ERODES THE FOG
RESTRICTIONS AND RETURNS VFR.
VFR IS THEN FAVORED FOR THE REST OF THE TAF PERIOD WHILE
ADDITIONAL SCATTERED TO BROKEN CU DEVELOP BETWEEN 4-6 KFT AFTER
15Z WITH DIURNAL HEATING/MIXING. WIND REMAINS GENERALLY LIGHT
OUT OF THE NW AT 5-10 KNOTS. CU WILL COLLAPSE WITH SUNSET
TONIGHT GIVING WAY TO SCT CIRRUS COVERAGE AND LIGHT AND VARIABLE
WIND.
OUTLOOK...
SHOWER AND LOW PROBABILITY THUNDERSTORM CHANCES RETURN WEDNESDAY
INTO THURSDAY AHEAD OF A SLOWER MOVING COLD FRONT. EXPECT
WIDESPREAD RESTRICTIONS ASSOCIATED WITH THE FRONT BY THURSDAY
MORNING. PERIODIC RESTRICTION/RAIN CHANCES ARE FAVORED INTO THE
WEEKEND.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
DISCUSSION...HEFFERAN
AVIATION...FRAZIER/MLB
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