091
ACUS03 KWNS 010721
SWODY3
SPC AC 010720
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0220 AM CDT TUE SEP 01 2026
VALID 031200Z - 041200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
THE EASTERN OHIO VALLEY INTO THE MID-ATLANTIC...
..SUMMARY
AT LEAST WIDELY SCATTERED SEVERE STORMS, ACCOMPANIED BY DAMAGING
GUSTS AND PERHAPS SOME HAIL, APPEAR LIKELY ACROSS PORTIONS OF THE
OHIO VALLEY TO THE MID-ATLANTIC COAST ON THURSDAY.
..SYNOPSIS
UPPER RIDGING WILL PERSIST ACROSS THE MID-MS VALLEY AND POINTS EAST,
WITH MULTIPLE MID-LEVEL PERTURBATIONS EXPECTED TO CREST THE UPPER
RIDGE FROM THE UPPER MS VALLEY TO THE MID-ATLANTIC THROUGH THE DAY
THURSDAY. CURRENTLY, THE BEST CHANCE FOR SEVERE STORMS WILL BE WITH
THE PRIMARY IMPULSE OVER THE MID-ATLANTIC, AS STRONGER FLOW ALOFT
OVERSPREADS A MOIST BOUNDARY LAYER. A COUPLE OF SEVERE THUNDERSTORMS
ALSO CANNOT BE RULED OUT FARTHER NORTHWEST ACROSS THE UPPER MS
VALLEY, WHERE RICH LOW-LEVEL MOISTURE WILL BE COINCIDENT WITH A
DIFFUSE WARM FRONTAL BOUNDARY.
..OH VALLEY TO THE MID-ATLANTIC COASTLINE
MEDIUM-RANGE GUIDANCE IS IN GENERAL AGREEMENT THAT A MODEST
MID-LEVEL IMPULSE WILL OVERSPREAD THE MID-ATLANTIC, CONTRIBUTING TO
SOME FORCING FOR ASCENT AND 30-40 KTS OF EFFECTIVE BULK SHEAR.
DESPITE ONLY 6 C/KM MID-LEVEL LAPSE RATES, SURFACE DEWPOINTS
EXCEEDING 70 F WILL YIELD OVER 2000 J/KG MLCAPE FROM THE EASTERN OH
VALLEY TO THE MID-ATLANTIC COASTLINE ON A WIDESPREAD BASIS. WHILE
UPPER SUPPORT MAY BE WEAKER COMPARED TO THE PREVIOUS DAY, MULTIPLE
DAYS OF PRECEDING STORMS SHOULD LEAVE BEHIND A LINGERING BAROCLINIC
BOUNDARY SOMEWHERE AROUND THE MID-ATLANTIC, WHICH MAY ACT AS A
FORCING MECHANISM FOR CONVECTIVE INITIATION. GIVEN THE
AFOREMENTIONED CAPE/SHEAR PARAMETER SPACE, SUPERCELLS AND BOWING
SEGMENTS MAY OCCUR, CAPABLE OF PRODUCING MAINLY A SEVERE GUST
THREAT, THOUGH A COUPLE INSTANCES OF SEVERE HAIL MAY OCCUR.
SOME GUIDANCE SUGGESTS THAT THE BEST BUOYANCY/SHEAR PARAMETER SPACE
FOR SEVERE MAY SITUATE OVER EASTERN PA INTO NJ. HOWEVER, IT IS
UNCLEAR HOW PREVIOUS DAY'S STORMS WILL IMPACT THE BOUNDARY LAYER
OVER THIS REGION BY DAY 3/THURSDAY, SO SLIGHT RISK PROBABILITIES
WERE INTRODUCED CONSERVATIVELY, WITH SOME LATITUDE GIVEN TO THE
NORTHERN EXTENT OF THE MARGINAL RISK PROBABILITIES. IF THE MORE
AGGRESSIVE GUIDANCE HOLDS TRUE AND CONVECTIVE OVERTURNING DOES NOT
DOMINATE THIS REGION, HIGHER SEVERE PROBABILITIES MAY BE NEEDED IN
FUTURE OUTLOOKS.
..PORTIONS OF THE UPPER MS VALLEY TO THE MIDWEST
CONVECTIVE INITIATION IS MORE UNCERTAIN ACROSS PORTIONS OF THE
MIDWEST TO THE UPPER MS VALLEY, WHERE A NORTHWESTWARD ARCHING WARM
FRONT WILL BE LOCATED. HERE, SURFACE DEWPOINTS SHOULD REACH THE MID
70S F BENEATH 7 C/KM MID-LEVEL LAPSE RATES, YIELDING 3500-4500 J/KG
MLCAPE. WHILE SEVERAL CALIBRATED ML/AI GUIDANCE MEMBERS DEPICT
HIGHER SEVERE PROBABILITIES ACROSS THIS REGION, ONLY MARGINAL RISK
PROBABILITIES HAVE BEEN INTRODUCED SINCE THE MID-LEVEL IMPULSES
POISED TO TRACK ALONG THIS BOUNDARY ARE QUITE SMALL AND SUBTLE,
RENDERING STORM COVERAGE HIGHLY QUESTIONABLE. NONETHELESS, IF A
STORM CAN MATURE AND BECOME SUSTAINED, 40+ KTS OF EFFECTIVE BULK
SHEAR WITH THE STRONG INSTABILITY MAY SUPPORT A SUPERCELL OR TWO
CAPABLE OF MAINLY SEVERE WIND AND HAIL.
..SQUITIERI.. 09/01/2026
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