SWODY2
SPC AC 251712
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1212 PM CDT WED MAY 25 2011
VALID 261200Z - 271200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE ERN U.S.
FROM THE CNTRL GULF STATES TO UPSTATE NY...
...EASTERN U.S...
STRONG CLOSED LOW SITUATED OVER THE CNTRL PLAINS DAY1 WILL EJECT EWD
INTO THE OH VALLEY AND BECOME AN OPEN WAVE BY 27/00Z AS STRONGEST
MID LEVEL FLOW TRANSLATES INTO THE UPPER OH VALLEY. THIS SCENARIO
WILL ENSURE THAT BROAD SSWLY FLOW OVERSPREADS THE WARM SECTOR AHEAD
OF PROGRESSIVE COLD FRONT. THE STRONGEST DEEP LAYER SHEAR IS
EXPECTED TO FOCUS FROM THE TN VALLEY/SRN APPALACHIANS...NWD INTO
UPSTATE NY...AND THIS WILL BE THE PRIMARY ZONE WHERE ORGANIZED
SEVERE IS EXPECTED THURSDAY.
EARLY IN THE PERIOD...A CONSIDERABLE AMOUNT OF TSTM ACTIVITY SHOULD
BE NOTED...BOTH WITHIN THE STRONGEST REGION OF WARM ADVECTION ACROSS
NRN IND/SRN LOWER MI...AND SWD ALONG THE COLD FRONT INTO THE NCNTRL
GULF STATES. EXPECTATIONS ARE THAT EXTENSIVE CLOUDS/PRECIPITATION
MAY HOLD DOWN HEATING ALONG THE FRONTAL ZONE AND MORE SIGNIFICANT
BREAKS AND PARTIAL SUNSHINE MAY ACTUALLY OCCUR ROUGHLY 150-200 MI
DOWNSTREAM FROM GA...NWD INTO THE UPPER OH VALLEY. AS A
RESULT...LAPSE RATES WITH FRONTAL CONVECTION MAY NOT BE THAT STEEP.
GREATEST BUOYANCY WILL BE NOTED ACROSS THE HIGHER ELEVATIONS INTO
UPSTATE NY WELL AHEAD OF PRIMARY WIND SHIFT. THE MAIN CONCERN WITH
THIS AXIS OF INSTABILITY WILL BE THE LACK OF SIGNIFICANT LOW LEVEL
CONVERGENCE. EVEN SO...STRONG DIURNAL HEATING WELL IN ADVANCE OF
THE FRONT SHOULD PROVE ADEQUATE FOR AT LEAST ISOLATED SEVERE
THUNDERSTORMS ACROSS AFOREMENTIONED ZONE OF STRONGER INSTABILITY.
FARTHER WEST...FRONTAL CONVECTION WILL DEFINITELY BE STRONGER FORCED
BUT INSTABILITY SHOULD BE SOMEWHAT WEAKER DUE TO MARGINAL LAPSE RATE
ENVIRONMENT. OVERALL...DEEP SWLY FLOW ON THE ORDER OF 40KT SHOULD
ENHANCE THE PROSPECT FOR ORGANIZED LINE SEGMENTS AND PERHAPS EVEN
EMBEDDED SUPERCELL STRUCTURES. DAMAGING WINDS WILL BE THE PRIMARY
SEVERE CONCERN WITH STRONGER BOW STRUCTURES...THOUGH ISOLATED STORMS
THAT MANAGE TO DEVELOP ACROSS THE UPPER OH VALLEY INTO UPSTATE NY
WILL BE CONSIDERABLY SHEARED AND POTENTIALLY MORE SUPERCELLULAR IN
NATURE DURING THE DAYTIME PRIOR TO FRONTAL PASSAGE.
...NRN/CNTRL HIGH PLAINS...
VERY DIFFLUENT HIGH LEVEL FLOW WILL OVERSPREAD THE NRN ROCKIES INTO
THE HIGH PLAINS AS A FOCUSED ZONE OF ASCENT EJECTS ACROSS MT/WY
TOWARD THE BLACK HILLS REGION. A PRONOUNCED SHORTWAVE TROUGH SHOULD
ENCOURAGE CONVECTION ACROSS THE PLAINS OF SERN MT...SWD INTO NERN CO
BY MID-LATE AFTERNOON AS FORCING INTERACTS WITH MODESTLY STEEP LAPSE
RATES/SUFFICIENTLY MOIST ENVIRONMENT. ALTHOUGH SFC DEW POINTS WILL
ONLY BE IN THE 40S ACROSS THIS REGION...FORECAST SOUNDINGS SUGGEST
SBCAPE COULD RANGE FROM 500-900 J/KG WHERE SHEAR PROFILES WILL
DEFINITELY SUPPORT DEEP STORM ROTATION. ALTHOUGH A FEW WEAK
SUPERCELLS COULD DEVELOP ACROSS THIS REGION...WEAK INSTABILITY
WARRANTS MAINTAINING 5% PROBS PRIMARILY FOR HAIL.
..DARROW.. 05/25/2011
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