DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 111624
SWODY1
SPC AC 111622

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1122 AM CDT MON JUN 11 2012

VALID 111630Z - 121200Z

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT
FROM PORTIONS OF THE OZARK PLATEAU AND MID MS VALLEY INTO SRN
PLAINS...LOWER MS VALLEY AND MID SOUTH...

...SYNOPSIS...

PROMINENT UPPER TROUGH OVER MANITOBA WILL PROGRESS EWD INTO ONTARIO
THIS PERIOD WITH AN ASSOCIATED VORTICITY MAXIMUM AND 60-70 KT
MIDLEVEL JET STREAK MOVING THROUGH THE UPPER MS VALLEY INTO UPPER
GREAT LAKES. MEANWHILE...A WEAKER...LOWER-LATITUDE IMPULSE WILL
PROGRESS FROM THE CNTRL PLAINS THROUGH THE MID MS VALLEY. FARTHER
TO THE SE...UPPER TROUGH OVER THE TN VALLEY AND GULF COAST STATES
WILL PHASE WITH A POLAR BRANCH IMPULSE MOVING THROUGH THE OH
VALLEY...EFFECTIVELY SUPPRESSING MIDLEVEL RIDGE AXIS IN PLACE FROM
THE LOWER GREAT LAKES TO SERN ATLANTIC COAST.

AT THE SURFACE...COLD FRONT FROM THE UPPER MIDWEST TO SRN HIGH
PLAINS WILL PROGRESS EWD/SEWD THROUGH THE UPPER GREAT LAKES AND MID
MS VALLEY. THE SWRN EXTENSION OF THE FRONT IS FORECAST TO BECOME
QUASI-STATIONARY TODAY ACROSS WRN TX/ERN NM.

...OZARK PLATEAU/MID MS VALLEY INTO LOWER MS VALLEY/MID SOUTH...

12Z REGIONAL SOUNDINGS INDICATE THE POTENTIAL FOR STRONG AIR MASS
DESTABILIZATION TODAY ALONG ERN EDGE OF STRONGER SRN PLAINS CAP
WHERE VERY STEEP MIDLEVEL LAPSE RATES COINCIDE WITH RICH BOUNDARY
LAYER MOISTURE. WHILE MID AND HIGH-LEVEL WIND FIELD DECREASES WITH
SWD EXTENT ACROSS THE REGION...THE COMBINATION OF MLCAPE VALUES OF
2500-3500 J/KG AND A ROBUST COLD POOL ASSOCIATED WITH MATURE MCS
OVER SRN MO SHOULD SUSTAIN SYSTEM SEWD TODAY INTO THE LOWER MS
VALLEY/MID SOUTH WITH THE POTENTIAL FOR SWATHS OF DAMAGING WINDS AND
LARGE HAIL. ADDITIONAL OCCURRENCES OF HIGH WINDS AND HAIL WILL BE
POSSIBLE WITH SECONDARY LINEAR CONVECTIVE SYSTEM MOVING FROM THE MID
MS INTO LOWER OH VALLEY.

...SRN PLAINS...

AS MENTIONED ABOVE...12Z SOUNDINGS SHOWED THE PRESENCE OF A STRONG
CAP ASSOCIATED WITH AN EML WITH NEARLY DRY ADIABATIC LAPSE
RATES...RESIDING ABOVE A VERY MOIST BOUNDARY LAYER. THE RESULTANT
THERMAL STRATIFICATION WILL YIELD AN EXTREMELY UNSTABLE AIR MASS
THIS AFTERNOON WITH MLCAPE VALUES APPROACHING 4000-5000 J/KG.
MORNING WATER VAPOR IMAGERY SHOWS A WEAK MIDLEVEL PERTURBATION ALONG
THE RED RIVER WHICH WILL CONTINUE ESEWD INTO THE ARKLATEX WITH
LITTLE IN THE WAY OF LARGE-SCALE FORCING FOR ASCENT ANTICIPATED
UPSTREAM OF THIS FEATURE. AS SUCH...IT APPEARS THAT STRONG BOUNDARY
LAYER HEATING AND CONVERGENCE ALONG THE FRONT /AND WRN EXTENSION OF
OZARK PLATEAU MCS OUTFLOW BOUNDARY/ WILL BE THE PRIMARY MECHANISMS
FORCING STORM DEVELOPMENT LATER THIS AFTERNOON INTO EVENING.

GIVEN STORM INITIATION AND SUSTENANCE...THE EXTREME INSTABILITY AND
30-35 KT OF DEEP-LAYER SHEAR WILL SUPPORT INTENSE UP/DOWNDRAFTS WITH
THE POTENTIAL FOR VERY LARGE HAIL AND DAMAGING WINDS. WITH
TIME...GROWING STORM-SCALE COLD POOLS MAY FOSTER UPSCALE GROWTH INTO
AN MCS WITH THE WIND/HAIL THREAT CONTINUING INTO TONIGHT.

...SERN STATES...

FORCING FOR ASCENT ASSOCIATED WITH UPPER LOW WILL AUGMENT LOW-LEVEL
CONVERGENCE ALONG EXISTING CONVECTIVE OUTFLOW BOUNDARIES TO FOSTER A
STEADY INCREASE IN STORM COVERAGE TODAY WITHIN A VERY MOIST AND
MODERATELY UNSTABLE AIR MASS. AREA WSR-88D VAD DATA AND FORECAST
HODOGRAPHS ACROSS WARM SECTOR EXHIBIT A UNIDIRECTIONAL OR WEAKLY
VERTICALLY VEERING WIND PROFILE WITH MODEST /20-30 KT/ DEEP...SWLY
SHEAR. AS SUCH...THE POTENTIAL WILL EXIST FOR LINE SEGMENTS AND
MULTICELL CLUSTERS CAPABLE OF ISOLATED OCCURRENCES OF DAMAGING
WINDS.

...MIDWEST/UPPER GREAT LAKES...

CONVERGENCE ALONG COLD FRONT AND EXISTING CONVECTIVE OUTFLOW
BOUNDARIES IN COMBINATION WITH FORCING ATTENDANT TO VORTICITY MAXIMA
MENTIONED IN SYNOPSIS WILL GIVE RISE TO WIDELY SCATTERED TSTMS THIS
AFTERNOON FROM ERN WI/NRN IL INTO LOWER MI AND IND. PERSISTENT
CLOUDS ARE EXPECTED TO TEMPER THE DEGREE OF AIR MASS
DESTABILIZATION...AND THE STRONGEST MID AND HIGH-LEVEL WIND FIELD
WILL LAG WARM SECTOR TO THE WEST...BOTH OF WHICH WILL MODULATE
SEVERE WEATHER POTENTIAL. NONETHELESS...ISOLATED SEVERE STORMS WILL
REMAIN POSSIBLE THIS AFTERNOON INTO EVENING WITH A RISK FOR LOCALLY
DAMAGING WINDS AND SOME HAIL.

..MEAD/ROGERS.. 06/11/2012

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