878
FXUS61 KPBZ 192338
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
738 PM EDT WED AUG 19 2026
WHAT HAS CHANGED
SATURATED GROUNDS AND HIGHER PROBABILITIES FOR HEAVY RAIN HAVE
RAISED THE RISK FOR LOCALIZED FLASH FLOODING TONIGHT INTO
THURSDAY. A FLOOD WATCH IS NOW IN EFFECT.
KEY MESSAGES
1) SLIGHTLY HIGHER RISK FOR FLASH FLOODING OVERNIGHT TONIGHT
INTO THURSDAY MORNING WITH POTENTIAL TRAINING OF HEAVIER RAIN
STORMS. A FLOOD WATCH HAS BEEN ISSUED.
2) ADDITIONAL ROUNDS OF RAIN FAVORED OVER THE WEEKEND WITH
LIMITED HAZARDOUS WEATHER RISKS.
DISCUSSION
KEY MESSAGE 1...
A WEAK FRONTAL BOUNDARY DROPPING OUT OF SOUTHERN MI WILL COMBINE
WITH LIMITED MID-LEVEL SHORTWAVE MOVEMENT TO CREATE LOW
PROBABILITY SHOWER AND THUNDERSTORM CHANCES MAINLY NEAR THE I-80
CORRIDOR THIS AFTERNOON TO EARLY EVENING. EVEN AS THE FRONT
STALLS SOMEWHERE NEAR THE I-70 CORRIDOR THIS EVENING, AREA
CLOUD COVER AND MINIMAL BUOYANCY (LESS THAN 700 J/KG SBCAPE)
SHOULD KEEP ANY ACTIVITY FAIRLY ISOLATED.
GREATER ORGANIZATION OF UPPER TROUGHING OVER THE SOUTHERN OH
RIVER VALLEY LATE TONIGHT INTO THURSDAY MORNING RESULTS IN MORE
WIDESPREAD SHOWER (AND LOW PROBABILITY THUNDERSTORM) ACTIVITY.
THE COMBINATION OF THE STALLED SFC BOUNDARY SITTING PARALLEL TO
UPPER FLOW PLUS PWATS QUICKLY RISING TOWARDS THE 90TH PERCENTILE
AND JET DYNAMICS AIDING STRONGER MID-LEVEL FRONTOGENESIS CREATES
THE POTENTIAL FOR A NARROW CORRIDOR OF ENHANCED RAINFALL
RATES/ACCUMULATIONS AS STORMS SIT AND TRAIN OVER SIMILAR
LOCATIONS. 00Z HREF PROBABILITIES OF 6-HR ACCUMULATIONS
EXCEEDING 2" WITHIN A 40KM RADIUS HAS RISEN TOWARDS 40-60% IN A
RELATIVE AXIS FROM MUSKINGUM COUNTY (OH) THROUGH BUTLER COUNTY
(PA), MEANING THIS SECTOR IS MORE LIKELY TO SEE RAIN TOTALS THAT
COULD RAISE FLASH FLOOD RISKS. A FLOOD WATCH HAS BEEN ISSUED
FOR PORTIONS OF EASTERN OH, NORTHERN WV, AND EXTREME SOUTHWEST
PA WHERE RECENT HEAVY RAIN EVENTS HAVE LOCALLY INCREASED
VULNERABILITY TO FLASH FLOODING.
CONVECTIVE ACTIVITY SHIFTS EAST OF THE REGION WITH THE EMBEDDED
SHORTWAVE THROUGH THE DAY THURSDAY AND GENERALLY SUPPORTS THE
END OF PRECIPITATION CHANCES. KEEP AN EYE FOR A RE-INTRODUCTION
OF POPS THURSDAY NIGHT AS RESIDUAL SAGGING TROUGHING TO THE WEST
PLUS RESIDUAL MOISTURE COULD BE ENOUGH FOR ISOLATED SHOWERS.
KEY MESSAGE 2...
SURFACE HIGH PRESSURE CROSSING THE GREAT LAKES PORTENDS TO DRY
WEATHER FRIDAY BEFORE THE NEXT LOW PRESSURE SYSTEM WITH A
DEEPENING UPPER TROUGH INTRODUCTION THE NEXT RAIN CHANCES
SATURDAY AFTERNOON INTO SUNDAY. SOME VARIANCE REMAINS IN THE
WAVE TIMING WHICH COULD ALTER THE PEAK PRECIPITATION PERIOD, BUT
THIS FLOW WILL RESULT IN FAIRLY WIDESPREAD SHOWERS WITH LOWER
PROBABILITY THUNDERSTORMS ALONG WITH SLIGHT AREA TEMPERATURE
FALLS.
THE MAIN HAZARD RISK, IF ONE WERE TO DEVELOP, OCCURS WITH
AFTERNOON FRONTAL PASSAGE SATURDAY WHILE ENOUGH HEATING/MOISTURE
RETURNS PUSHES BUOYANCY VALUES HIGH ENOUGH TO OFFER A LOWER
PROBABILITY WIND RISK. OTHERWISE, ENSEMBLE GUIDANCE IS TRENDING
TOWARD A DRIER START TO THE FOLLOWING WEEK.
AVIATION /00Z THURSDAY THROUGH MONDAY/
CLOUDS ARE BEGINNING TO INCREASE OVER THE FORECAST AREA AT THIS
TIME AS AN UPPER SHORTWAVE NEARS THE AREA. MOISTURE STRUNG OUT
ALONG A SFC FRONT IS BRINGING MAINLY VFR SHOWERS INTO CENTRAL OH
NEARING ZZV. EMBEDDED IN THESE SHOWERS ARE BRIEF IFR DOWNPOURS.
THIS ACTIVITY IS EXPECTED TO SHIFT EASTWARD OVER THE COMING
HOURS AND SLOWLY LOSE INTENSITY. AS SUCH BRIEF WINDOWS OF IFR IN
DOWNPOURS OR VFR SHOWERS REMAIN POSSIBLE AT HLG AND PIT/AGC
WITH DECLINING LIKELIHOOD (REPRESENTED WITH TEMPOS) THE FURTHER
EAST YOU GO INTO THE RETREATING DRY AIR.
RAINFALL INTENSITY INCREASES OVERNIGHT AS SURFACE CYCLOGENESIS
TAKES PLACE IN OH AND RENEWED MVFR SHOWERS WITH POSSIBLE IFR OR
EVEN LIFR DOWNPOURS CROSS THE REGION FROM WEST TO EAST BEGINNING
NEAR DAWN IN ZZV. LIMITED INSTABILITY LIKELY PRECLUDES
WIDESPREAD THUNDER BUT A RUMBLE OR TWO REMAINS POSSIBLE.
MUCH OF THE OVERNIGHT RAIN LIKELY OCCURS IN VFR CIGS APART FROM
BENEATH THE HEAVIEST DOWNPOURS. BY SUNRISE, TOP DOWN MOISTENING
BRINGS CIGS DOWN WITH LOW END MVFR/IFR CIGS APPEARING LIKELY AT
MOST PORTS. SHOWERY ACTIVITY AND CIGS BEGIN TO BREAK AND RISE
TOMORROW AFTERNOON AS THE LOW PASSES. PROB30 GROUPS REMAIN FOR
LINGERING SHOWERS AT A NUMBER OF SITES.
OUTLOOK...
DRIER CONDITIONS AND PREVAILING VFR RETURN THURSDAY AFTERNOON
AND CONTINUE THROUGH EARLY SATURDAY, WITH THE EXCEPTION OF
PATCHY FOG/STRATUS POSSIBLE DURING OVERNIGHT AND EARLY MORNING
HOURS. RESTRICTIONS AND RAIN CHANCES ARE FAVORED TO RETURN LATE
SATURDAY INTO SUNDAY AS ANOTHER DISTURBANCE CROSSES THE REGION.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...FLOOD WATCH THROUGH THURSDAY AFTERNOON FOR PAZ029-031.
OH...FLOOD WATCH THROUGH THURSDAY AFTERNOON FOR OHZ039-040-048>050-
057>059-068-069.
WV...FLOOD WATCH THROUGH THURSDAY AFTERNOON FOR WVZ001>004-012-021-
509.
DISCUSSION...CERMAK/FRAZIER
AVIATION...AK
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