074
ACUS01 KWNS 042005
SWODY1
SPC AC 042003
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0303 PM CDT FRI SEP 04 2026
VALID 042000Z - 051200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE SOUTHERN
GREAT LAKES INTO THE MID-ATLANTIC STATES...
..SUMMARY
A COUPLE OF ORGANIZED THUNDERSTORM CLUSTERS ARE EXPECTED TO DEVELOP
ACROSS THE SOUTHERN GREAT LAKES AND MID/UPPER OHIO VALLEY THROUGH
TONIGHT, ACCOMPANIED BY THE RISK FOR DAMAGING WIND GUSTS. MORE
WIDELY SCATTERED STRONG THUNDERSTORMS EAST OF THE BLUE RIDGE MAY
ALSO PRODUCE DAMAGING WIND GUSTS THIS EVENING.
..20Z UPDATE
THE NORTHERN PORTION OF THE MARGINAL RISK WAS EXPANDED WESTWARD INTO
PORTIONS OF NORTHEASTERN IOWA TO ACCOUNT FOR RECENT CONVECTIVE
DEVELOPMENT ASSOCIATED WITH A MID-LEVEL PERTURBATION VISIBLE ON
WATER VAPOR SATELLITE IMAGERY. AN UNSTABLE AIRMASS AND MODEST
DEEP-LAYER SHEAR WILL SUPPORT LOOSELY ORGANIZED CONVECTION, CAPABLE
OF PRODUCING ISOLATED OCCURRENCES OF 60 MPH WINDS AND 1-INCH HAIL.
ELSEWHERE, THE WESTERN PORTION OF THE SLIGHT RISK AREA WAS EXPANDED
ACROSS ILLINOIS, INDIANA, AND PORTIONS OF OHIO, WHERE THUNDERSTORMS
HAVE DEVELOPED ALONG A SURFACE BOUNDARY AND MAY POSE AN INCREASED
THREAT FOR 55-70 MPH WIND GUSTS AND 1-INCH HAIL. SEE MCDS #2234 AND
#2235 FOR MORE DETAIL.
FURTHER DOWNSTREAM ACROSS NORTH CAROLINA, THE SEVERE WIND
PROBABILITIES WERE EXTENDED SOUTHWARD TO ACCOUNT FOR RECENT
CONVECTIVE TRENDS. A CORRIDOR OF HIGHER WIND PROBABILITIES WAS
CONSIDERED ACROSS PORTIONS OF VIRGINIA, BUT UNCERTAINTY IN THE
LONGEVITY OF THE CONVECTION MOVING ACROSS THE APPALACHIANS AND
OVERALL CONVECTIVE ORGANIZATION PRECLUDED ADDING ADDITIONAL
HIGHLIGHTS AT THIS TIME.
THE 30% WIND THREAT AREA IS EXPECTED TO SEE CONVECTIVE DEVELOPMENT
LATER THIS EVENING, AS STORMS MOVE FROM THE GREAT LAKES INTO THE
REGION. THERE IS SOME UNCERTAINTY IN THE NORTHWARD EXTENT OF THE
AREA OWING TO THE DROP OFF IN BUOYANCY, BUT CONTINUED SPREAD IN THE
HIGH-RESOLUTION FORECAST GUIDANCE REGARDING THE TIMING AND PLACEMENT
OF CONVECTION PRECLUDES ADDITIONAL ADJUSTMENTS AT THIS TIME.
CONVECTION IS ALSO ANTICIPATED TO DEVELOP ACROSS PORTIONS OF
NORTH-CENTRAL NEBRASKA INTO SOUTH DAKOTA DURING THE EARLY MORNING
HOURS. THESE STORMS COULD PRODUCE ISOLATED OCCURRENCES OF HAIL,
THOUGH UNCERTAINTY IN THE TIMING OF CONVECTIVE INITIATION AND
MATURATION SUGGESTS THIS WILL PRIMARILY POSE A THREAT IN THE DAY 2
TIME FRAME.
..HALBERT/WEINMAN.. 09/04/2026
PREV DISCUSSION
/ISSUED 1146 AM CDT FRI SEP 04 2026/
..MIDWEST/SOUTHERN GREAT LAKES TO MID-ATLANTIC STATES
AS LARGE-SCALE PATTERN AMPLIFICATION OCCURS, A BELT OF MODERATELY
STRONG NORTHWESTERLY FLOW ALOFT WILL TEND TO OVERLIE A FRONTAL ZONE
THAT EXTENDS FROM SOUTHERN PORTIONS OF MINNESOTA/WISCONSIN
EAST-SOUTHEASTWARD TO PENNSYLVANIA/NEW JERSEY. THAT SAID, ONGOING
CONVECTION HAS EFFECTIVELY MODIFIED/SOUTHWARD-SHUNTED THE EFFECTIVE
FRONT IN SEVERAL AREAS, AND THIS WILL BE THE PRIMARY FOCUS FOR STORM
INTENSIFICATION/REDEVELOPMENT THIS AFTERNOON, AS WELL INTO THE
EVENING/LATE NIGHT.
THE STEEPER MID-LEVEL LAPSE RATES WILL REMAIN DISPLACED WEST OF THE
REGION, BUT AMPLE LOW-LEVEL MOISTURE (I.E. UPPER 60S/LOW 70S
DEWPOINTS) COUPLED WITH AFTERNOON TEMPERATURES FROM THE MID 80S TO
MID 90S WILL STILL SUPPORT MODERATE TO STRONG BUOYANCY NEAR/SOUTH OF
THE EFFECTIVE BOUNDARY. GENERAL STORM RE-INTENSIFICATION AND/OR NEW
DEVELOPMENT IS ANTICIPATED THIS AFTERNOON, PARTICULARLY SOUTH/AHEAD
OF CURRENTLY ONGOING CLUSTERS. BOWING LINE SEGMENTS WILL BE THE
PREDOMINANT STORM MODE, WITH DAMAGING WINDS AS THE MOST COMMON
HAZARD.
THE THREAT FOR DAMAGING WIND GUSTS WILL EXTEND SOUTHEASTWARD INTO
THE MID-ATLANTIC THIS AFTERNOON AND EVENING AMID A VERY WARM AND
MOIST AIRMASS. VERTICAL SHEAR WILL BE WEAKER WITH SOUTHWARD EXTENT,
BUT AMPLE MOISTURE (I.E. PW VALUES FROM 1.8" TO 2"), STRONG
BUOYANCY, AND STEEP LOW-LEVEL LAPSE RATES WILL SUPPORT THE POTENTIAL
FOR STRONG OUTFLOW CAPABLE OF WIND DAMAGE. BOWING LINE
SEGMENTS WILL BE THE PRIMARY STORM MODE HERE AS WELL.
..SOUTHERN WISCONSIN/SOUTHERN LAKE MICHIGAN VICINITY
THE SAME GENERAL METEOROLOGICAL THEMATIC SCENARIO AS DESCRIBED IN
THE PRIOR SECTION APPLIES TO THIS REGION, AND SEVERE PROBABILITIES
HAVE BEEN EXTENDED WESTWARD REGIONALLY, ALBEIT FOR A SOMEWHAT
CONDITIONAL/UNCERTAIN SCENARIO. A ROBUST RESERVOIR OF
MOISTURE/LOCALLY EXTREME BUOYANCY WILL EXIST PARTICULARLY TO THE
SOUTH OF ONGOING MIDDAY CONVECTION. THE REGION WILL BE INFLUENCED BY
THE AMPLIFYING UPPER RIDGE, BUT THERE IS AT LEAST SOME POSSIBILITY
THAT STORM REDEVELOPMENT/INTENSIFICATION COULD OCCUR NEAR/EAST OF
THE SURFACE TRIPLE POINT AND/OR NEAR OUTFLOW, WITH SOME RELATED
SEVERE POTENTIAL. DEVELOPMENT COULD ALSO OCCUR TOWARD THE SOUTHERN
LAKE MICHIGAN VICINITY LATER TONIGHT AS ISENTROPIC ASCENT INCREASES
NEAR/NORTHEAST OF THE SURFACE BOUNDARY.
..NORTH-CENTRAL PLAINS/DAKOTAS
WHILE PERCEIVED SEVERE PROBABILITIES REMAIN BELOW 5%, SOME
STRONG/SPORADIC SEVERE POTENTIAL MAY EXIST ALSO SOUTH DAKOTA, FAR
NORTHERN NEBRASKA AND/OR SOUTHEAST NORTH DAKOTA LATER TODAY THROUGH
LATE TONIGHT, ALTHOUGH CONFIDENCE IN SPECIFIC METEOROLOGICAL
SCENARIOS REMAINS LOW.
WEAK LEE TROUGHING WILL CONTRIBUTE TO MODEST LOW-LEVEL CONVERGENCE
FROM WESTERN KANSAS ACROSS WESTERN/CENTRAL NEBRASKA INTO SOUTHWEST
SOUTH DAKOTA. DEWPOINTS WILL LIKELY BE IN THE LOW TO MID 60S F
WITHIN THIS CONVERGENCE ZONE, AND STEEP MID-LEVEL LAPSE RATES WILL
CONTRIBUTE TO MODERATE/STRONG BUOYANCY. EVEN SO, WARM MID-LEVELS MAY
PREVENT THE AIRMASS FROM COMPLETELY DESTABILIZING. THE REMAINING
CONVECTIVE INHIBITION, COUPLED WITH THE PRESENCE OF LARGE-SCALE
HEIGHT RISES ACROSS THE REGION, CASTS DOUBT TO WHETHER SUCCESSFUL
CONVECTIVE INITIATION WILL OCCUR. ANY MATURE UPDRAFTS COULD RESULT
IN STRONG DOWNDRAFT, BUT UNCERTAINTY REMAINS HIGH. OTHER STORM
DEVELOPMENT COULD OCCUR TONIGHT, POTENTIALLY AS A BYPRODUCT OF A
SUBTLE MID-LEVEL WAVE/ONGOING CONVECTION ONGOING ACROSS SOUTH DAKOTA
THIS MORNING.
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