656
FXUS61 KPBZ 170003
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
803 PM EDT WED SEP 16 2026
WHAT HAS CHANGED
NO LARGE SCALE CHANGES ACCOMPANY THE LATEST FORECAST PACKAGE AS
FOCUS REMAINS ON A FAIRLY ACTIVE WEATHER PATTERN INTO NEXT WEEK.
KEY MESSAGES
1) A FEW WAVES OF SHOWERS AND THUNDERSTORMS THIS AFTERNOON
THROUGH THURSDAY OFFER RISKS FOR FLASH FLOODING ALONGSIDE A
NOMINAL WIND THREAT.
2) UNSETTLED WEATHER RETURNS LATE SATURDAY INTO NEXT WEEK.
DISCUSSION
KEY MESSAGE 1...
AS SOUTHERLY TO SOUTHWESTERLY SURFACE FLOW CONTINUES TO PUSH
AREA DEWPOINTS INTO THE UPPER 60S TO LOWER 70S, MOIST WESTERLY
FLOW AHEAD OF AN INCOMING SHORTWAVE IS HELPING TO PUSH AREA
ABOVE 1.8" NORTH OF I-70 (AS LOW AS 1.5" SOUTH). THIS WARM,
MOIST AIRMASS (WHOSE PWATS ARE NEAR TO ABOVE THE DAILY MAX
VALUES FOR MID SEPTEMBER) IS SETTING THE TEMPLATE FOR A SHOWER
AND THUNDERSTORM ENVIRONMENT CAPABLE OF LOCALIZED FLASH FLOODING
THIS AFTERNOON INTO THURSDAY. AIDING FLOOD RISK FACTORS INCLUDE
SLOW STORM MOTION LESS THAN 20KTS (PROLONGING HEAVY RAIN
DURATION AT A GIVEN LOCATION), WARM-RAIN PROCESSES (ABOVE
FREEZING LAYER DEPTH OF 15KFT AIDS RAINFALL EFFICIENCY), AND
MODEST CAPE AROUND 1500 J/KG (WITH A BULK WITHIN THE WARM CLOUD
LAYERS THAT WOULD HELP RAINFALL RATES REACH 1-2"/HR). THOUGH
STORM INITIATION/COVERAGE CONFIDENCE IS LOW (SEE NEXT
PARAGRAPH), THE STATIONARY SURFACE BOUNDARY UNDERNEATH WESTERLY
FLOW ALOFT WITHIN THE ABNORMALLY WARM, HUMID AIRMASS COULD
RESULT IN TRAINING OF STORMS THAT RESULTS IN FLASH FLOODING.
THE LACK OF A FLOOD WATCH IS TIED TO UNCERTAINTIES PRESENT
CAUSED BY THE LIMITED LIFT AND JET SUPPORT IN THE REGION. WHILE
A SURFACE STATIONARY BOUNDARY NEAR LAKE ERIE CAN ACT AS A
FORCING MECHANISM, THE MID-LEVEL JET IS FAIRLY DISPLACED
NORTHWARD SUCH THAT IT OFFERS LITTLE FOR STORM
INITIATION/COVERAGE. ADDITIONALLY, WEAK SHEAR (AROUND 10-15KTS)
MAY LIMIT UPDRAFT ORGANIZATION SO STORMS EITHER DON'T MAXIMIZE
RAINFALL INTENSITY OR MAINTAIN LONG-ENOUGH DURATION FOR RAINFALL
TO REACH EVEN THE LOWER FLASH FLOOD GUIDANCE. FINALLY,
INCREASING CLOUD COVER TONIGHT INTO THURSDAY SHOULD REDUCE
BUOYANCY ENOUGH TO AGAIN LIMIT EFFICIENCY/STORM DEPTH EVEN AS
SHEAR IMPROVES BY THURSDAY. GIVEN THESE FACTORS AND THE LACK OF
A CONSENSUS OF FOCUS FOR REPETITIVE STORMS, NO FLOOD WATCH HAS
BEEN ISSUED DESPITE VARIOUS INGREDIENTS BEING IN PLACE.
BEYOND THE FLOODING THREAT, THERE IS A NOMINAL DAMAGING WIND
RISK THIS AFTERNOON/EVENING IF A LOCALIZED STORM MAXIMIZES
AVAILABLE ENERGY AND TAPS INTO SOME POCKETS OF DRIER AIR ALOFT
(ABOVE ~20KFT). THE LACK OF SHEAR MEANS A SEVERE STORM WOULD
LIKELY BE A MICROBURST WITH PRECIPITATION-LOADING ALOFT, BUT LOW
PROBABILITIES OF MATCHING THESE CONDITIONS MEANS THREATS ARE
UNLIKELY AND MOSTLY ISOLATED IN NATURE.
KEY MESSAGE 2...
SURFACE HIGH PRESSURE WITHIN BRIEF NW FLOW SUPPORTS AT LEAST 1
DAY OF DRY WEATHER AS TEMPERATURE DROPS BELOW THE 80S (BUT
REMAINS ABOVE NORMAL). BUT THE LONGWAVE PATTERN IS FAVORED BY
ENSEMBLE MODELS TO POSITION UPPER RIDGING OVER THE TENNESSEE TO
LOWER MISSISSIPPI RIVER VALLEYS WHILE DRIVING A SERIES OF
SHORTWAVES OVER THE RIDGE TOP THROUGH THE OHIO RIVER VALLEY. THE
RESULT IS MORE WAVES OF SHOWERS AND THUNDERSTORMS THROUGH EARLY
NEXT WEEK THAT, PENDING THE LOCALIZED STORM ENVIRONMENT FOR A
GIVEN DAY, COULD CONTAIN VARIOUS HAZARD THREATS.
THE MOST LIKELY HAZARDOUS RISK OVER THIS TIME FRAME IS FLASH
FLOOD GIVEN GUIDANCE MAINTAINS MEAN PWAT VALUES BETWEEN 1.4" TO
1.9" INCHES (BETWEEN THE 90TH TO ABOVE DAILY MAX, RESPECTIVELY).
THIS RISK COULD BE FURTHER EXACERBATED IF THE REGION DOES
EXPERIENCE MULTIPLE ROUNDS OF HEAVY RAIN (EVEN STARTING
TONIGHT/THURSDAY) THAT CAUSES NEAR-SATURATED GROUNDS THAT
SIGNIFICANTLY LOWERS FLASH FLOOD GUIDANCE. IT MAY BE
METEOROLOGICAL FALL, BUT SUMMER-LIKE STORM RISKS BEAR MONITORING
INTO EARLY NEXT WEEK.
AVIATION /00Z THURSDAY THROUGH MONDAY/
VFR PREVAILS THROUGH THIS EVENING WITH THE EXCEPTION OF BRIEF
REDUCTIONS IN VISIBILITY DURING TIMES WHEN SCATTERED SHOWERS AND
THUNDERSTORMS IMPACT AREA TERMINALS. PREVAILING CEILINGS EVENTUALLY
DROP TO MVFR FROM NORTH TO SOUTH (IFR POSSIBLE AT FKL/DUJ),
THOUGH THERE REMAINS LINGERING UNCERTAINTY REGARDING JUST HOW
FAR THE LOW CLOUD DECK ADVANCES. LATEST GUIDANCE SUGGESTS IT
REACHES THE I-70 CORRIDOR EARLY TO MID MORNING THURSDAY, SO
MAINTAINED THAT TIMING IN THIS TAF CYCLE. THERE IS A CHANCE THAT
THE LOWER CEILING DOES NOT MOVE FURTHER SOUTH THAN PIT. OUTSIDE
OF THUNDERSTORMS, WINDS REMAIN LIGHT AND VARIABLE OVERNIGHT
THEN WESTERLY DURING THE DAY THURSDAY.
ADDITIONAL WAVES OF SCATTERED SHOWERS AND STORMS ARE EXPECTED
THURSDAY, WITH MORE CHANCES FOR TEMPORARY REDUCTIONS IN CEILINGS
AND VISIBILITIES.
OUTLOOK...
IMPROVEMENT TO VFR IS LIKELY FRIDAY UNDER HIGH PRESSURE. SATURDAY
NIGHT, RESTRICTIONS ARE LIKELY TO RETURN WITH AN INCREASE CHANCE
FOR SHOWERS AND THUNDERSTORMS ASSOCIATED WITH AN APPROACHING
DISTURBANCE.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...NONE.
OH...NONE.
WV...NONE.
DISCUSSION...FRAZIER
AVIATION...CERMAK/LUPO
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