DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 231630
SWODY1
SPC AC 231628

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1128 AM CDT WED MAY 23 2012

VALID 231630Z - 241200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MIDWEST AND
CENTRAL PLAINS INTO NERN CO...

...THERE IS A SLGT RISK OF SVR TSTMS OVER ERN PARTS OF THE CAROLINAS
INTO SERN VA...

...UPPER MIDWEST INTO THE CENTRAL PLAINS...
UPPER LOW OVER SRN CANADIAN PRAIRIES IS FORECAST TO REMAIN
QUASI-STATIONARY THROUGH THE PERIOD AS SEVERAL PERTURBATIONS
PROGRESS EWD WITHIN THE BAND OF THE STRONG MID/UPPER LEVEL WINDS
FROM THE GREAT BASIN INTO THE PLAINS. WATER VAPOR IMAGERY SHOWS ONE
SHORT WAVE TROUGH FROM ERN WY INTO NERN UT...AND THIS IS EXPECTED TO
MOVE INTO THE PLAINS TONIGHT AND PROVIDE INCREASING SUPPORT FOR
CONVECTIVE DEVELOPMENT. AT THE SURFACE...A COLD FRONT FROM THE ERN
DAKS/MN BORDER SWWD INTO NWRN KS AND CENTRAL CO IS EXPECTED TO MOVE
SLOWLY EWD/SEWD AS INCREASING SWLY FLOW ALOFT BECOMES MORE PARALLEL
TO THE FRONTAL ORIENTATION.

12Z SOUNDINGS SHOW A VERY WELL-DEFINED EML OVER THE PLAINS WITH VERY
WARM 700 MB TEMPERATURES OF 15C AT LBF...DDC AND AMA. THE EML IS
LIKELY TO INHIBIT SURFACE-BASED CONVECTIVE DEVELOPMENT AHEAD OF THE
FRONT...WITH MODEL GUIDANCE GENERALLY INDICATING THAT STORMS WILL
INITIATE ALONG/BEHIND THE FRONT LATER THIS AFTERNOON FROM SWRN MN
SWWD INTO ERN NEB. MOISTURE CONTINUES TO BE MODEST WITH PW VALUES
OF 1.0-1.25 INCHES AND SURFACE DEW POINTS REMAINING IN THE 55-60F
RANGE. VERY STEEP LAPSE RATES ARE EXPECTED TO DEVELOP THROUGH A
DEEP LAYER AHEAD OF THE FRONT AS STRONG DIABATIC HEATING STEEPENS
LOW LEVEL LAPSE RATES RESULTING IN A DEEP WELL-MIXED BOUNDARY LAYER.
STRENGTHENING MID/UPPER LEVEL WINDS WILL GRADUALLY OVERSPREAD THE
CENTRAL PLAINS INTO THE UPPER MIDWEST...CONTRIBUTING TO 40-50 KT
DEEP LAYER SHEAR SUPPORTIVE OF ORGANIZED CONVECTIVE STRUCTURES
INCLUDING SUPERCELLS. VERY LARGE HAIL AND DAMAGING WIND GUSTS WILL
BE THE PRIMARY SEVERE THREATS FROM LATE AFTERNOON THROUGH THE
EVENING HOURS...ALTHOUGH AN ISOLATED TORNADO OR TWO MAY ALSO BE
POSSIBLE FOR STORMS THAT FORM CLOSE TO THE FRONT. ACTIVITY IS
EXPECTED TO PROGRESS SLOWLY EWD/SEWD TONIGHT...BUT LARGELY REMAINING
ALONG/NORTH OF THE FRONT...ENHANCED BY A STRONG NOCTURNAL LOW LEVEL
JET OVER THE PLAINS/MO VALLEY.

...NERN CO INTO CENTRAL HIGH PLAINS...
GUIDANCE INDICATES A SURFACE LOW WILL DEVELOP OVER SERN CO WITH A
STRONG ENELY SURFACE PRESSURE GRADIENT DEVELOPING OVER ERN CO.
RESULTANT UPSLOPE FLOW WILL ADVECT MOISTURE WWD TOWARD THE FOOTHILLS
AND CONTRIBUTE TO DESTABILIZATION THIS AFTERNOON AS STRONG HEATING
OCCURS EAST OF THE MOUNTAINS. WITH SURFACE DEW POINTS INCREASING
INTO THE MID-UPPER 40S...MUCAPE IS EXPECTED TO REACH 500-1000 J/KG.
LOW LEVEL UPSLOPE WINDS COUPLED WITH DIVERGENCE ALOFT ASSOCIATED
WITH THE LEFT EXIT REGION OF THE STRONG UPPER JET WILL ENHANCE
THUNDERSTORM POTENTIAL THIS AFTERNOON AND EVENING. STRONGLY VEERING
WIND PROFILES WITH HEIGHT WILL ENHANCE ORGANIZATION AND INTENSITY OF
CONVECTION WITH STRONG/SEVERE STORMS EXPECTED INCLUDING A FEW
SUPERCELLS. LARGE HAIL...DAMAGING WIND GUSTS AND AN ISOLATED
TORNADO OR TWO WILL BE POSSIBLE. ACTIVITY MAY GROW UPSCALE INTO AN
EWD MOVING MCS THAT MOVES INTO PARTS OF THE CENTRAL PLAINS LATER
TONIGHT.

...ERN CAROLINAS INTO SERN VA...
WATER VAPOR IMAGERY INDICATES COLD UPPER LOW /-16C AT 500 MB/ IS
LIFTING NEWD FROM SC TOWARD ERN NC AND IS EXPECTED TO ENHANCE
THUNDERSTORM ACTIVITY AGAIN THIS AFTERNOON. VISIBLE IMAGERY SHOWS
CLOUDS ARE CLEARING/THINNING OVER PARTS OF NC IN ADVANCE OF THE
SYSTEM...WHICH IS ALLOWING STRONG HEATING/DESTABILIZATION TO OCCUR.
ALTHOUGH WINDS ALOFT AND VERTICAL SHEAR WILL REMAIN MARGINALLY
SUPPORTIVE FOR ORGANIZED CONVECTIVE STRUCTURES...VERY FAVORABLE
THERMODYNAMIC ENVIRONMENT SUGGESTS POTENTIAL FOR SEVERE STORMS TO
DEVELOP THIS AFTERNOON AND EVENING CAPABLE OF PRODUCING LARGE HAIL
AND LOCALIZED DAMAGING WIND GUSTS.

.....LOWER MS VALLEY...
STRONG HEATING AMIDST A NEWD-ADVANCING WARM FRONT WILL SUPPORT
ISOLATED TO WIDELY SCATTERED TSTMS. BOUNDARY-LAYER DEWPOINTS IN THE
60S NEAR AND SW OF THE FRONT WILL SUPPORT MODERATE TO STRONG
DESTABILIZATION...WITH STEEP LOW-LEVEL LAPSE RATES LIKELY YIELDING
DCAPE VALUES IN EXCESS OF 1000 J/KG. VERY WEAK FLOW THROUGHOUT THE
TROPOSPHERE WILL SUPPORT A PULSE CONVECTIVE MODE...AND A LOW THREAT
FOR DMGG WIND GUSTS AND PERHAPS MARGINALLY SVR HAIL CANNOT BE RULED
OUT WITH THE STRONGEST STORMS.

..WEISS/GARNER.. 05/23/2012

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