039
ACUS02 KWNS 031657
SWODY2
SPC AC 031655
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1155 AM CDT THU SEP 03 2026
VALID 041200Z - 051200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE UPPER OHIO VALLEY INTO THE SOUTHERN MID-ATLANTIC...
..SUMMARY
WIDELY SCATTERED SEVERE THUNDERSTORMS, MAINLY PRODUCING DAMAGING
GUSTS, ARE EXPECTED ACROSS PORTIONS OF THE UPPER OHIO VALLEY INTO
THE SOUTHERN MID-ATLANTIC ON FRIDAY. MORE ISOLATED SEVERE STORMS
CAPABLE OF SEVERE WINDS AND LARGE HAIL MAY OCCUR OVER PARTS OF THE
MIDWEST FRIDAY AFTERNOON INTO NIGHT.
..SYNOPSIS
A MID-LEVEL RIDGE OVER CENTRAL NORTH AMERICA WILL UNDERGO
CONSIDERABLE AMPLIFICATION BETWEEN TROUGHS LOCATED OVER THE WESTERN
CONUS AND EASTERN CANADA INTO THE NORTHEAST. SUBTLE DISTURBANCES
EMBEDDED WITHIN THE BROADER-SCALE FLOW REGIME WILL FOCUS
THUNDERSTORM DEVELOPMENT, ONE OF WHICH WILL PROGRESS FROM THE GREAT
LAKES INTO THE MID-ATLANTIC ON FRIDAY.
AT THE SURFACE, A LEE CYCLONE WILL DEVELOP OVER THE NORTHERN HIGH
PLAINS WITH AN ASSOCIATED SURFACE FRONT STRETCHING FROM THE NORTHERN
PLAINS THROUGH THE UPPER MIDWEST AND GREAT LAKES TO THE MID-ATLANTIC
COAST. THE SPECIFIC LOCATION OF THAT BOUNDARY BY AFTERNOON MAY BE
AFFECTED BY CONVECTIVE OUTFLOW ASSOCIATED WITH THUNDERSTORM ACTIVITY
TONIGHT INTO FRIDAY MORNING.
..UPPER OHIO VALLEY TO SOUTHERN MID-ATLANTIC
THERE IS GOOD AGREEMENT ACROSS 12Z MODEL GUIDANCE THAT THUNDERSTORMS
WILL BE ONGOING AT 12Z FRIDAY OVER PORTIONS OF THE GREAT LAKES AHEAD
OF THE MID-LEVEL DISTURBANCE MENTIONED ABOVE. A SUBSET OF THOSE
STORMS MAY LINGER THROUGH THE MORNING OVER THE UPPER OH VALLEY WITH
AN ASSOCIATED RISK FOR DAMAGING WIND GUSTS.
BY AFTERNOON, DAYTIME HEATING ACROSS THE DOWNSTREAM AIR MASS OVER
THE SOUTHERN MID-ATLANTIC WILL COMBINE WITH BOUNDARY-LAYER DEWPOINTS
IN THE LOW/MID 70S TO YIELD MODERATE INSTABILITY WITH MLCAPE UP TO
2000-2500 J/KG. THAT DESTABILIZATION PROCESS, IN CONJUNCTION WITH
INCREASED FORCING FOR ASCENT ASSOCIATED WITH THE APPROACHING
MID-LEVEL DISTURBANCE, WILL SUPPORT INTENSIFICATION OF ANY LINGERING
STORMS MOVING INTO THE REGION FROM THE NORTHWEST. ADDITIONAL STORMS
ARE ALSO POSSIBLE ALONG THE EFFECTIVE SURFACE FRONT AND LEE TROUGH.
THE PRESENCE OF 25-35 KT OF WEST-NORTHWEST DEEP-LAYER SHEAR WILL BE
SUFFICIENT FOR EPISODIC SUPERCELL AND BOWING STRUCTURES WITH THE
PREDOMINANT HAZARD BEING DAMAGING WIND GUSTS INTO EVENING.
A MODEST AREAL EXPANSION OF THE SLIGHT RISK WIND PROBABILITIES HAS
BEEN APPLIED TO PORTIONS OF THE UPPER OH VALLEY GIVEN THE SCENARIO
DESCRIBED ABOVE.
..MIDWEST
OWING TO THE PROXIMITY OF THE BUILDING MID-LEVEL RIDGE AND RESULTANT
CAPPING FOR SURFACE-BASED PARCELS, CONVECTIVE EVOLUTION REMAINS
HIGHLY UNCERTAIN. THE EASTERN EXTENSION OF A STEEP MID-LEVEL LAPSE
RATE PLUME WILL OVERLIE LOWER/MID 70S DEWPOINTS IN THE VICINITY OF
THE SURFACE FRONT, SUPPORTING MODERATE TO STRONG INSTABILITY BY
AFTERNOON WITH MLCAPE OF 3000-4000+ J/KG. THE 12Z
CONVECTION-ALLOWING AND PARAMETERIZED MODEL GUIDANCE OFFERS VARYING
SCENARIOS WITH RESPECT TO THE TIMING AND LOCATION OF STORM
DEVELOPMENT FROM FRIDAY AFTERNOON THROUGH NIGHT. DEEP-LAYER SHEAR
WILL BE WEAKER THAN PREVIOUS DAYS; HOWEVER, THE MAGNITUDE OF
INSTABILITY WILL BE SUPPORTIVE OF A CONDITIONAL RISK FOR LARGE HAIL
AND DAMAGING WINDS WITH ANY SURFACE-BASED STORMS THAT CAN DEVELOP.
MARGINAL RISK WIND AND HAIL PROBABILITIES WILL BE MAINTAINED IN THIS
FORECAST UPDATE DUE TO THE UNCERTAINTIES MENTIONED ABOVE.
..MEAD.. 09/03/2026
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