843
ACUS01 KWNS 012002
SWODY1
SPC AC 012000
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT TUE SEP 01 2026
VALID 012000Z - 021200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
SOUTHERN NEW YORK INTO THE MID-ATLANTIC...AND THE NORTHERN/CENTRAL
PLAINS INTO THE UPPER MIDWEST...
..SUMMARY
SCATTERED STRONG TO SEVERE THUNDERSTORMS SHOULD OCCUR THIS AFTERNOON
INTO TONIGHT ACROSS PARTS OF THE NORTHERN/CENTRAL PLAINS AND UPPER
MIDWEST, AND PARTS OF SOUTHERN NEW YORK INTO THE MID-ATLANTIC. LARGE
HAIL AND DAMAGING WINDS SHOULD BE THE MAIN THREATS.
..20Z UPDATE
ONLY MINOR CHANGES WERE MADE WITH THIS UPDATE. THE MRGL RISK WAS
EXPANDED SLIGHTLY SOUTHWARD INTO NORTHWEST KS, WHERE AN EVOLVING
STORM AND ADDITIONAL TOWERING CUMULUS WILL POSE A RISK OF ISOLATED
LARGE HAIL AND LOCALLY SEVERE GUSTS -- AIDED BY AN ELONGATED
HODOGRAPH (AROUND 30 KT OF EFFECTIVE SHEAR) AND SUFFICIENT BUOYANCY.
IN THE NORTHERN/CENTRAL PLAINS, SOME CONSIDERATION WAS GIVEN TO
ADDING 30-PERCENT WIND PROBABILITIES IN PARTS OF SOUTHEAST SD,
NORTHEAST NE, AND NORTHWEST IA. HERE, GUIDANCE IS IN GOOD AGREEMENT
THAT AN UPSCALE-GROWING CLUSTER WILL POSE A RELATIVELY GREATER
SEVERE-WIND RISK. HOWEVER, GIVEN THE LATE EXPECTED TIMING, HIGHER
PROBABILITIES WERE WITHHELD AT THIS TIME.
FOR DETAILS ON THE NEAR-TERM SEVERE RISK, SEE MCDS 2184 AND 2185.
..WEINMAN.. 09/01/2026
PREV DISCUSSION
/ISSUED 1128 AM CDT TUE SEP 01 2026/
..MID-ATLANTIC/SOUTHERN NEW YORK
A MID/UPPER-LEVEL ANTICYCLONE WILL REMAIN CENTERED OVER THE TN
VALLEY/MID-SOUTH TODAY, WITH A MID-LEVEL SHORTWAVE TROUGH FORECAST
TO MOVE EASTWARD ACROSS ONTARIO THROUGH THE PERIOD. IN BETWEEN THESE
FEATURES, A BELT OF ENHANCED WEST-NORTHWESTERLY FLOW WILL EXIST
ACROSS THE GREAT LAKES INTO THE MID-ATLANTIC. LATEST SURFACE
OBSERVATIONS SHOW A FRONT DRAPED FROM NORTHWEST TO SOUTHEAST ACROSS
SOUTHERN NY/NEW ENGLAND, WITH CLOUD COVER AND PRECIPITATION ONGOING
ACROSS THESE AREAS. CURRENT EXPECTATIONS ARE FOR DESTABILIZATION TO
OCCUR ALONG/SOUTH OF THE FRONT THROUGH THE AFTERNOON, WITH MODESTLY
STEEPENED MID-LEVEL LAPSE RATES PRESENT ACROSS MI (REFERENCE 12Z
OBSERVED APX/DTX SOUNDINGS) FORECAST TO ADVECT SOUTHEASTWARD ACROSS
THE MID-ATLANTIC. MODERATE TO STRONG INSTABILITY WILL LIKELY DEVELOP
BY MID AFTERNOON ACROSS PA/NJ, WITH 30-40 KT OF DEEP-LAYER SHEAR
FOSTERING UPDRAFT ORGANIZATION.
WHILE THERE IS STILL SOME UNCERTAINTY REGARDING OVERALL CONVECTIVE
DEVELOPMENT AND EVOLUTION THIS AFTERNOON/EVENING OWING TO NEBULOUS
LARGE-SCALE ASCENT, MOST HIGH-RESOLUTION GUIDANCE DEVELOPS ISOLATED
TO WIDELY SCATTERED THUNDERSTORMS ALONG/SOUTH OF THE FRONT,
PARTICULARLY OVER EASTERN PA INTO NJ AND VICINITY. SUPERCELLS WITH A
SEVERE HAIL/WIND THREAT WILL BE POSSIBLE INITIALLY, AND ENOUGH
LOW-LEVEL SHEAR MAY EXIST NEAR THE FRONT FOR A TORNADO OR TWO AS
WELL. WHETHER CONVECTION CAN GROW UPSCALE INTO ONE OR MORE CLUSTERS
ALSO REMAINS UNCERTAIN. BUT IF THIS OCCURS, THEN THE THREAT FOR
DAMAGING WINDS MAY INCREASE LATE THIS AFTERNOON INTO THE EVENING
GIVEN THE RATHER FAVORABLE ENVIRONMENT FORECAST.
..NORTHERN/CENTRAL PLAINS INTO THE UPPER MIDWEST/GREAT LAKES
A MID-LEVEL SHORTWAVE TROUGH OVER THE NORTHERN/CENTRAL ROCKIES AND
ADJACENT HIGH PLAINS THIS MORNING WILL TRANSLATE NORTHEASTWARD TODAY
OVER THE NORTHERN/CENTRAL PLAINS. A MOIST AND UNSTABLE AIRMASS WILL
RESIDE ALONG/SOUTH OF A FRONT FORECAST TO EXTEND GENERALLY WEST TO
EAST ACROSS PARTS OF SOUTHERN SD/NORTHERN NE INTO SOUTHERN
MN/NORTHERN IA. ROBUST THUNDERSTORM DEVELOPMENT APPEARS INCREASINGLY
LIKELY BY 21-23Z ACROSS NORTH-CENTRAL NE AS LARGE-SCALE ASCENT
PRECEDING THE SHORTWAVE TROUGH OVERSPREADS THE DESTABILIZING WARM
SECTOR. LATEST NAM/RAP FORECAST SOUNDINGS ACROSS THIS REGION SHOW UP
TO 1500-2500 J/KG OF MLCAPE AND STRONG DEEP-LAYER SHEAR, WHICH WILL
LIKELY SUPPORT SUPERCELLS INITIALLY. WITH STEEPENED LOW/MID-LEVEL
LAPSE RATES AND ELONGATED/NEARLY STRAIGHT HODOGRAPHS AT MID LEVELS
DEPICTED, SOME POTENTIAL FOR 2+ INCH HAIL MAY EXIST WITH THESE
SUPERCELLS. A TORNADO OR TWO ALSO APPEARS POSSIBLE AS LOW-LEVEL
SHEAR GRADUALLY INCREASES AFTER 02/00Z. WITH TIME, A BOWING CLUSTER
IS EXPECTED TO DEVELOP ACROSS EASTERN SD/NORTHEAST NE THIS EVENING,
AND SUBSEQUENTLY TRACK EASTWARD ACROSS SOUTHERN MN/NORTHERN IA WITH
A SEVERE/DAMAGING WIND THREAT OVERNIGHT. SOME RISK FOR DAMAGING
WINDS AND HAIL MAY CONTINUE INTO EARLY WEDNESDAY MORNING ACROSS
PARTS OF WI AND LOWER MI AS WELL.
..COASTAL SOUTHEAST TEXAS/SOUTHWEST LOUISIANA
TROPICAL STORM EDOUARD WILL CONTINUE TRACKING NORTHWESTWARD TODAY,
PER LATEST NHC FORECASTS. SOME ENHANCEMENT TO THE LOW-LEVEL WIND
FIELD AND HODOGRAPH IS NOTED ON THE LATEST VWP AND 15Z SPECIAL
OBSERVED SOUNDING FROM KLCH. THIS MAY SUPPORT TRANSIENT UPDRAFT
ROTATION WITH ANY CELLS ON THE NORTH TO NORTHEAST SIDE OF EDOUARD'S
CIRCULATION, AND A BRIEF TORNADO OR TWO MAY OCCUR THIS
AFTERNOON/EVENING ACROSS PARTS OF COASTAL SOUTHEAST TX/SOUTHWEST LA
AS FILTERED DIURNAL HEATING SUPPORTS MODEST DESTABILIZATION.
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