045
ACUS02 KWNS 011732
SWODY2
SPC AC 011730
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1230 PM CDT TUE SEP 01 2026
VALID 021200Z - 031200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER THE EASTERN
GREAT LAKES INTO MID-ATLANTIC AND OVER THE NORTHERN ROCKIES...
..SUMMARY
SEVERE THUNDERSTORMS ARE POSSIBLE ACROSS PORTIONS OF THE EASTERN
GREAT LAKES TO THE MID-ATLANTIC WEDNESDAY INTO WEDNESDAY NIGHT.
DAMAGING WIND GUSTS ARE THE MAIN THREAT, THOUGH SOME LARGE HAIL AND
A FEW TORNADOES MAY ALSO OCCUR. WIDELY SCATTERED SEVERE GUSTS AND
MORE SPORADIC OCCURRENCES OF LARGE HAIL APPEAR POSSIBLE FROM THE
NORTHERN ROCKIES INTO NORTHERN HIGH PLAINS WEDNESDAY AFTERNOON INTO
NIGHT.
..SYNOPSIS
A BELT OF 40-50+ KT MID-LEVEL WINDS WILL SPREAD FROM THE GREAT LAKES
INTO THE NORTHEAST IN TANDEM WITH A SERIES OF LOW-AMPLITUDE
DISTURBANCES. ELSEWHERE, A NEGATIVELY TILTED SHORTWAVE TROUGH AND
ATTENDING MID-LEVEL JET STREAK WILL PROGRESS THROUGH THE NORTHERN
ROCKIES WEDNESDAY AFTERNOON AND EVENING. AT THE SURFACE, THE PRIMARY
BAROCLINIC ZONE IS EXPECTED TO EXTEND FROM LOW PRESSURE OVER JAMES
BAY THROUGH THE GREAT LAKES AND MID MO VALLEY INTO THE NORTHERN HIGH
PLAINS. A BACKDOOR FRONT/QUASI-STATIONARY BOUNDARY WILL RESIDE OVER
THE MID-ATLANTIC, THE SPECIFIC LOCATION OF WHICH WILL BE DICTATED BY
THE EXTENT OF OUTFLOW ASSOCIATED WITH EARLY-DAY STORMS AND THE
STRENGTH OF LOW-LEVEL RIDGING STRETCHING FROM THE GULF OF ST.
LAWRENCE THROUGH THE NORTHEAST.
..GREAT LAKES INTO THE MID-ATLANTIC
AS ALLUDED TO IN THE SYNOPSIS, THUNDERSTORMS MAY BE ONGOING AT 12Z
WEDNESDAY FROM PORTIONS OF WI AND MI INTO NY AND PA WITHIN A ZONE OF
FORCING FOR ASCENT ASSOCIATED WITH A LEAD SHORT-WAVE TROUGH. THE
STRONGEST STORMS WILL BE CAPABLE OF ISOLATED OCCURRENCES OF LARGE
HAIL AND/OR DAMAGING WINDS AS THEY SPREAD EAST-SOUTHEAST THROUGH THE
LOWER GREAT LAKES AND MID-ATLANTIC WEDNESDAY MORNING. IN THE WAKE OF
THE EARLY-DAY CONVECTION, PREVAILING WEST-NORTHWEST MID-LEVEL FLOW
WILL MAINTAIN A PLUME OF RELATIVELY STEEP MID-LEVEL LAPSE RATES
(E.G., 7 C/KM) ATOP BOUNDARY LAYER DEWPOINTS IN THE UPPER 60S TO LOW
70S, YIELDING MLCAPE UPWARDS OF 2000-3000+ J/KG BY AFTERNOON FROM
LOWER MI INTO WESTERN PARTS OF NY AND PA.
ADDITIONAL THUNDERSTORMS ARE EXPECTED DURING THE AFTERNOON FROM
LOWER MI THROUGH THE LOWER GREAT LAKES, AIDED BY WEAK DISTURBANCES
ALOFT AND THE MODERATE TO STRONG INSTABILITY FORECAST ACROSS THE
WARM SECTOR. THE PRESENCE OF 35-45 KT OF EFFECTIVE BULK SHEAR WILL
SUPPORT ORGANIZED STORM MODES INCLUDING SUPERCELLS AND BOWING
STRUCTURES CAPABLE OF LARGE HAIL POTENTIALLY APPROACHING TWO INCHES
AND DAMAGING WIND GUSTS INTO WEDNESDAY NIGHT. TORNADO POTENTIAL WILL
BE CONDITIONAL ON STORM MODE; HOWEVER, THE MODELS DO INDICATE
STRONGER LOW-LEVEL WINDS AND RESULTANT LARGER SRH DEVELOPING FROM
SOUTHWEST ON INTO NY AND PA WEDNESDAY AFTERNOON INTO EVENING, WHERE
THE GREATEST POTENTIAL FOR A FEW TORNADOES WILL EXIST.
..NORTHERN ROCKIES INTO NORTHERN HIGH PLAINS
THE PRESENCE OF STEEP LOW/MID-LEVEL LAPSE RATES AND FORCING FOR
ASCENT ATTENDANT TO THE SHORT-WAVE TROUGH ARE EXPECTED TO FOSTER AN
INCREASE IN THUNDERSTORMS OVER WESTERN MT WEDNESDAY AFTERNOON AMIDST
A KINEMATIC ENVIRONMENT FEATURING AROUND 30 KT OF SOUTHERLY
DEEP-LAYER SHEAR. NAM AND RAP-BASED FORECAST SOUNDINGS INDICATE THE
PRESENCE OF A RELATIVELY DEEP, WELL-MIXED BOUNDARY LAYER, WHICH WILL
ENHANCE SEVERE-WIND-GUST POTENTIAL, ESPECIALLY AS STORMS MERGE INTO
CLUSTERS. GIVEN THE STRENGTH OF THE SHORT-WAVE TROUGH AND CONSISTENT
MODEL SIGNAL FOR SCATTERED STORMS IN A FAVORABLE THERMODYNAMIC
ENVIRONMENT, AN UPGRADE TO LEVEL-2/SLIGHT RISK WAS INCLUDED IN THIS
FORECAST.
ADDITIONAL STORMS APPEAR POSSIBLE ACROSS PORTIONS OF EASTERN MT INTO
WESTERN ND WEDNESDAY EVENING WITHIN A ZONE OF WARM ADVECTION ALONG A
NOCTURNALLY STRENGTHENING LOW-LEVEL JET. ISOLATED OCCURRENCES OF
LARGE HAIL APPEAR TO BE THE PRIMARY HAZARD WITH THOSE STORMS.
..MID MO VALLEY INTO IA AND SOUTHERN MN
NEUTRAL TO SLIGHT MID-LEVEL HEIGHT RISES ARE FORECAST ACROSS THE
REGION WEDNESDAY AFTERNOON INTO NIGHT WITH THE NEBULOUS FORCING FOR
ASCENT LEADING TO UNCERTAINTY IN WHETHER STORMS WILL DEVELOP NEAR
THE SURFACE BOUNDARY. AS SUCH, NO SEVERE WEATHER PROBABILITIES WILL
BE INCLUDED IN THIS FORECAST, DESPITE A FAVORABLE OVERLAP OF
MODERATE TO STRONG INSTABILITY AND SUFFICIENT VERTICAL SHEAR.
..MEAD.. 09/01/2026
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