474
FXUS61 KPBZ 160521
AFDPBZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PITTSBURGH PA
121 AM EDT SUN AUG 16 2026
WHAT HAS CHANGED
MCS CURRENTLY MOVING THROUGH FORECAST AREA AND ADJUSTING NEAR
TERM DISCUSSION FOR THIS.
KEY MESSAGES
1) OVERNIGHT CLUSTER OF STORMS WILL BRING HEAVY RAINFALL AND
FLOOD POTENTIAL TO EASTERN OHIO, NORTHERN WEST VIRGINIA AND
POSSIBLY SOUTHWESTERN PENNSYLVANIA.
2) SUNDAY STORM EVOLUTION IS LOWER CONFIDENCE AS IT DEPENDS ON
THE EVOLUTION OF STORMS THROUGH DAWN, BUT FLASH FLOOD AND
SEVERE RISKS REMAIN POSSIBLE SUNDAY AFTERNOON WITH POTENTIAL
RENEWED STORMS.
3) AFTER LINGERING SHOWERS DISSIPATE MONDAY, THERE IS FAIRLY
HIGH CONFIDENCE IN DRY WEATHER UNTIL WEDNESDAY/THURSDAY, WHEN
LOW PRESSURE RETURNS.
DISCUSSION
KEY MESSAGE 1...
A WEAKENING MESOSCALE CONVECTIVE COMPLEX DRIVEN BY AN APPARENT
MCV CONTINUES TO TRACK ACROSS THE FORECAST AREA IN OHIO. HERE IN
THIS REGION, THE 2.0 TO 2.2 PWATS HAVE COME TO FRUITION AND
RAINFALL RATES OUT WEST SHOW SOME 1.5 TO 2.0 RAINFALL RATES. THE
SHORT TERM HI RES MODELS SHOW SOME UPTICK IN RAINFALL RATES AS
IT TRACKS EAST INTO THE THE WV PANHANDLE AND INTO ALLEGHENY
COUNTY.
HERE, THE HREF HINTS AT 1.00 TO 1.70 RAINFALL AMOUNTS FROM
MIDNIGHT THROUGH 10AM MOVING EAST INTO THE WV PANHANDLE AND THE
PA BORDER AND EVENTUALLY INTO ALLEGHENY COUNTY. THIS IS OF
COURSE ONLY THE MEAN VALUES AND HIGHER VALUES ARE CERTAINLY
POSSIBLE AND WILL THUS KEEP THE FLOOD WATCH GOING.
KEY MESSAGE 2...
CONFIDENCE IN WHAT FOLLOWS FOR SUN AND SUN NIGHT DROPS OFF, AS
ATMOSPHERIC RECOVERY/SUN-AFTERNOON STORM EVOLUTION WILL DEPEND
ON THE MESOSCALE SETUP LEFT BEHIND BY THE OVERNIGHT INTO SUNDAY
MORNING COMPLEX. WHILE STABLE MORNING AIR SHOULD LIMIT COVERAGE
AND INTENSITY OF CONVECTION AT LEAST INTO EARLY AFTERNOON,
REDEVELOPMENT APPEARS INCREASINGLY LIKELY TIED TO A POTENTIAL
MESOSCALE CONVECTIVE VORTEX DEVELOPING FROM STORMS IN THE
MIDWEST/NORTHERN PLAINS. THE ENSEMBLE MODELS SUCH AS THE LREF
SUGGEST A SECOND 500MB SHORTWAVE TRACKING ACROSS THE IN AND OH
REGION AND INTO THE FORECAST AREA. THIS MAY BE THE ONE NEEDED
TRIGGER TO HELP THE RECOVERY FORM THE MORNING CONVECTION.
HERE, A POCKET OF 25-30 KNOTS OF 0-6KM SHEAR COULD PROVIDE
ENOUGH STORM ORGANIZATION FOR A DAMAGING WIND POTENTIAL, WHILE
ELONGATED/CURVED LOW-LEVEL HODOGRAPHS (PARTICULARLY ENHANCED BY
A MCV IF PRESENT) AND SUFFICIENT 0-1KM SRH SUGGEST A LOWER-END
TORNADO THREAT FOR ESEWD-MOVING STORMS. ALTHOUGH THE INTERESTING
FACTOR HERE IS THAT THE CAMS CURRENTLY DO NOT PRODUCE AN
ORGANIZED MCS AND RATHER A CLUSTER OF STORMS DEVELOPING.
MACHINE- LEARNING GUIDANCE DOES SUPPORT THESE ASSERTIONS, LIKELY
PICKING UP ON MCV- ENHANCED FIELDS. ALSO, THE SAME FAVORABLE
HEAVY- RAINFALL INGREDIENTS FROM THE PREVIOUS NIGHT WILL
CONTINUE, EXTENDING THE FLASH FLOOD THREAT INTO SUN NIGHT.
ANOTHER NIGHT OF PWATS BETWEEN 2.0 AND 2.2 WILL KEEP A THREAT OF
FLOODING ACROSS THE AREA. THUS, THE FLOOD WATCH WILL CONTINUE.
KEY MESSAGE 3...
DIURNAL STABILIZATION SHOULD BEGIN TO LIMIT CONVECTIVE COVERAGE
AND INTENSITY LATE SUN EVENING, WITH A FEW SHOWERS LINGERING
INTO MON WITH ONE LAST SHORTWAVE TROUGH. BY THIS POINT, PWAT
WILL BE DROPPING OFF THANKS TO DEVELOPING DRIER NWLY FLOW,
WHICH SHOULD HELP TO TAPER THE HEAVY-RAINFALL THREAT. HIGH
PRESSURE BUILDING IN FROM THE GREAT LAKES SHOULD END
PRECIPITATION BY MON EVENING. DRY WEATHER IS THEN FAVORED UNTIL
WED, WHEN THE NEXT FRONT COULD POTENTIALLY ARRIVE, ALTHOUGH
THIS TIMING COULD CHANGE.
AVIATION /06Z SUNDAY THROUGH THURSDAY/
A WARM FRONT WILL APPROACH AND CROSS THE REGION EARLY THIS
MORNING, WITH SHOWERS, EMBEDDED THUNDERSTORMS, AND MVFR-IFR
RESTRICTIONS EXPECTED. ELEVATED BUOYANCY AND A LOW-LEVEL JET
SHOULD MAINTAIN AND EXPAND ONGOING STORMS AS THEY PROGRESS EWD
THRU MOST TERMINALS BY 11-13Z.
ALL TERMINALS LIKELY WILL SEE DEEP CONVECTIVE STORMS, ALTHOUGH
MANY MAY NOT FEATURE LIGHTNING. GIVEN THEIR STRUCTURE AND
INTENSITY, TSRA SEEMS MORE APPROPRIATE TO DESCRIBE THEIR
STRUCTURE OVERNIGHT TONIGHT.
IN THE WAKE OF THE MORNING RAIN, IFR RESTRICTIONS ARE EXPECTED
THRU AT LEAST MID-MORNING BEFORE SOME SUN AND ATMOSPHERIC
RECOVERY ENSUES. AFTERNOON THUNDERSTORMS THEN ARE LIKELY AS A
COLD FRONT APPROACHES, MAINLY AFTER 18Z. RESTRICTIONS ON VSBY
AND CIGS ARE LIKELY IN ANY OF THE AFTERNOON STORMS, AS HEAVY
RAIN AND LOW LCLS WILL BE COMMON.
FOG (IFR OR POSSIBLY BELOW) APPEARS LIKELY TO FORM SUN NIGHT AT
MOST TERMINALS, AS IS TYPICAL IN THE WAKE OF STORMS. HOW LOW
VSBY MAY GET SUN NIGHT WILL DEPEND ON WHETHER THE BOUNDARY
LAYER DECOUPLES MORE STRONGLY THAN CURRENTLY ANTICIPATED.
OUTLOOK...
A FEW SHOWERS AND RESTRICTIONS COULD CONTINUE MONDAY AS THE
COLD FRONT COMPLETES ITS PASSAGE. GENERAL VFR IS THEN EXPECTED
THROUGH TUE UNDER HIGH PRESSURE. RESTRICTIONS AND CHANCES FOR
SHOWERS/THUNDERSTORMS RETURN LATER WED INTO EARLY THU WITH THE
APPROACH AND PASSAGE OF ANOTHER COLD FRONT.
PBZ WATCHES/WARNINGS/ADVISORIES
PA...FLOOD WATCH THROUGH MONDAY MORNING FOR PAZ020-021-029-031-
073>076.
OH...FLOOD WATCH THROUGH MONDAY MORNING FOR OHZ039>041-048>050-
057>059-068-069.
WV...FLOOD WATCH THROUGH MONDAY MORNING FOR WVZ001>004-012-021-
509>514.
DISCUSSION...SHALLENBERGER
AVIATION...KRAMAR/WM/AK
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