919
FXUS61 KPBZ 181131
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
731 AM EDT FRI SEP 18 2026
WHAT HAS CHANGED
A CHANCE OF SHOWERS AND THUNDERSTORMS WILL STILL LINGER TODAY
BUT SOUTH OF I-70.
KEY MESSAGES
1) SOME LINGERING SHOWERS AND THUNDERSTORMS SOUTH OF I-70 TODAY.
2) ACTIVE WEATHER RETURNS STARTING SATURDAY INTO NEXT WEEK THAT
COULD PORTEND TO INCREASED FLOOD RISKS.
DISCUSSION
KEY MESSAGE 1...
EXPECT SOME MORNING FOG ACROSS THE AREA. SOME AREAS COULD SEE
SOME PATCHY DENSE FOG. THIS SHOULD BEGIN TO CLEAR UP BY 15Z. THE
FRIDAY PERIOD WILL FEATURE A MAINLY DRY FORECAST ACROSS THE
AREA WITH THE EXCEPTION OF THE REGION SOUTH OF I-70. THE COLD
FRONT HAS SETTLED SOUTH OF I-70 BUT STILL IMPACTING THE SOUTHERN
OH AND NORTHERN WV COUNTIES. EXPECT THE PROBABILITIES OF
RAINFALL TO EXCEED AN A HALF INCH BEING AROUND 10% TO 30%. THE
AFTERNOON CONVECTION SOUTH OF I-70 LOOKS TO WEAKEN AND DISSIPATE
BY THE 21Z TO 23Z TIME FRAME. OVERALL, A DRY DAY EXPECTED WITH
LITTLE TO NO IMPACTS.
KEY MESSAGE 2...
EXPECT MORE ROUNDS OF SHOWERS AND THUNDERSTORMS STARTING
SATURDAY INTO EARLY NEXT WEEK. THIS IS DUE TO THE REGION
GENERALLY SITTING ON THE NE PERIPHERY OF A LOWER MISSISSIPPI TO
TENNESSEE RIVER VALLEY HIGH WHILE A SERIES OF SHORTWAVES
TRAVERSE THE RIDGE TOP. ADDITIONALLY, WARM, MOIST ADVECTION
FAVORS A RETURN OF THE HUMID AIRMASS CHARACTERIZED BY
ANOMALOUSLY HIGH PWAT VALUES RANGING FROM 1.4"-1.9", ALL OF
WHICH IS ABOVE THE 90TH PERCENTILE. THOUGH FINER DETAILS VARY
MODEL-TO-MODEL AND DAY-TO-DAY (SOME DISCUSSED MOMENTARILY), THE
BROADER MESSAGING OF THIS PATTERN LENDS TO LIKELY PERIODS
FEATURING SHOWERS/THUNDERSTORM THAT CARRY AN INCREASED RISK FOR
FLASH FLOODING AND, PENDING OTHER ENVIRONMENTAL ASPECTS, SEVERE
WEATHER. THE SATURDAY PERIOD WILL FEATURE THE ARRIVAL OF
CONVECTION OVER THE NORTHWEST PORTION OF THE FORECAST AREA. THE
TIMING SEEMS TO BE MORE OF A SATURDAY NIGHT THREAT.
THE THREAT FOR FLASH FLOODING SEEMS TO BE IN A SATURDAY NIGHT TO
SUNDAY NIGHT PERIOD. THE ENSEMBLES HAVE BEEN TRENDING AND/OR BIA
TO LOWER RAINFALL TOTALS THROUGH THIS PERIOD AND IS VERY
NOTICEABLE. THIS IS TRUE EVEN FOR THE NBM. THUS, WILL EXPECT AN
MCS TO TRACK ACROSS THE AREA IN THE LATE SATURDAY NIGHT PERIOD.
CURRENT ENSEMBLE MEAN RAINFALL TOTAL VALUES OVER THIS 24-HOUR
PERIOD RANGE FROM 0.75"-1.5" WITH THE AXIS FAVORING THE I-80
CORRIDOR. PENDING THE POTENTIAL NORTH/SOUTH RE- POSITIONING OF
THIS AXIS, HIGH-END SCENARIOS COULD SEE TOTALS IN THE HEAVIEST
AXIS IN THE 2-3" RANGE; ANY ADDITIONAL CONVECTIVE ELEMENT BOOST
THEORETICALLY COULD PUSH THAT HIGHER. ENTERING THIS PERIOD, THE
REGION ALREADY IS FAIRLY SATURATED WITH LOWERED FLASH FLOOD
GUIDANCE; ANY RAIN THAT DEVELOPS AFTER THIS INITIAL WINDOW
LIKELY DOES WITH ALMOST FULLY SATURATED GROUNDS THAT SEES A HIGH
PERCENTAGE OF RAINFALL TRANSLATE TO RUN-OFF (INCREASING FLASH
FLOOD LIKELIHOOD). IF CONFIDENCE IN THESE OUTCOMES INCREASE,
FLOOD WATCHES MAY BE ISSUED IN THE COMING DAYS.
AVIATION /12Z FRIDAY THROUGH TUESDAY/
LOW STRATUS LINGERS ACROSS THE AREA THROUGH MORNING HOURS, THEN
GRADUALLY LIFTS TO VFR FROM NORTH TO SOUTH BY MID TO LATE
AFTERNOON. WINDS REMAIN OUT OF THE NORTH AROUND 5-10 KNOTS
THROUGHOUT THE DAY BEFORE SETTLING SOME AND VEERING TO MORE
NORTHEASTERLY OVERNIGHT INTO EARLY SATURDAY.
OUTLOOK...
RESTRICTIONS ARE LIKELY TO RETURN SATURDAY NIGHT INTO SUNDAY
MORNING WITH AN INCREASED CHANCE FOR SHOWERS AND THUNDERSTORMS
ASSOCIATED WITH AN APPROACHING DISTURBANCE.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
DISCUSSION...SHALLENBERGER
AVIATION...CERMAK/SHALLENBERGER
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