785
FXUS61 KPBZ 181744
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
144 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 /18Z TUESDAY THROUGH SUNDAY/
VFR EXPECTED FOR THE REST OF THE TAF PERIOD WITH 4-6 KFT BASED SCT
TO BKN DIURNAL CU. 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. SOME AREAS
OF RIVER VALLEY FOG ARE AGAIN POSSIBLE TONIGHT, BUT THINK IT
SHOULD BE A BIT LESS WIDESPREAD OUTSIDE OF THE VALLEYS TONIGHT
WITH DEW POINTS A TOUCH LOWER, SO HAVE LEFT MENTION OUT OF TAFS
FOR NOW. FKL AND DUJ WOULD BE THE MOST LIKELY SITES WITH IMPACTS
FROM FOG IF IT DEVELOPS.
MORE DIURNAL CU ARE EXPECTED ON WEDNESDAY WITH A 5-10 KNOT
WEST-SOUTHWEST WIND. SOME SHOWERS LIKELY RETURN JUST OUTSIDE
THE CURRENT TAF PERIOD WEDNESDAY NIGHT INTO THURSDAY ALONG AND
AHEAD OF A SLOW MOVING COLD FRONT.
OUTLOOK...
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...MLB
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