ACUS02 KWNS 070547
SWODY2
SPC AC 070546
DAY 2 CONVECTIVE OUTLOOK CORR 1
NWS STORM PREDICTION CENTER NORMAN OK
1246 AM CDT SAT MAY 07 2011
VALID 081200Z - 091200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE CNTRL/NRN PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE SRN HIGH PLAINS...
CORRECTED FOR PROBABILITY LINES
...SYNOPSIS...
UPPER FLOW REGIME WILL BECOME INCREASINGLY MERIDIONAL ON SUNDAY AND
FEATURE A DEEP TROUGH OVER THE N ATLANTIC AND A DIGGING IMPULSE OVER
THE WRN STATES. A WEAK MID-LEVEL SHORTWAVE TROUGH WILL EJECT ENE
AHEAD OF THE LATTER SYSTEM INTO THE CNTRL/SRN PLAINS BY SUNDAY
AFTERNOON. AT THE SFC...A COLD FRONT TIED TO THE ATLANTIC TROUGH
WILL SETTLE INTO THE CAROLINAS. TAIL END OF SAME FRONT WILL
REDEVELOP NWD AS A WARM FRONT FROM THE MIDWEST INTO THE DAKOTAS AS A
DRYLINE/LEE TROUGH STRENGTHENS ACROSS THE CNTRL/SRN HIGH PLAINS.
...CNTRL/NRN PLAINS TO THE MID-MS VLY...
BOUNDARY LAYER MOISTURE...CHARACTERIZED BY SFC DEW POINTS IN THE UPR
50S TO LWR 60S...WILL CIRCULATE ALONG NRN PERIPHERY OF A SFC
LOW/DRYLINE FROM THE CNTRL PLAINS/LWR MO VLY INTO CNTRL SD/WRN NEB
BY SUNDAY AFTN. A STRONG LID WILL EXIST ATOP THIS MOISTURE AS H7
TEMPERATURES SOAR TO 10-12 DEG C AS FAR N AS NEB/SD BORDER.
AS BOUNDARY LAYER DEEPENS/HEATS ACROSS THE HIGH PLAINS AND A WEAK
MID-LEVEL WAVE EJECTS NEWD...HIGH-BASED STORMS MAY FORM VICINITY THE
DRYLINE AND INVERTED TROUGH ACROSS WRN NEB AND SWRN SD NEWD INTO
CNTRL SD BY MID-AFTN. PRESENCE OF 2000-2500 J/KG MLCAPE AND 8-8.5
DEG C PER KM H5-H7 LAPSE RATES WILL YIELD SUPERCELLS WITH VERY LARGE
HAIL. A FEW OF THE STORMS MAY ROOT INTO THE MORE UNSTABLE
ENVIRONMENT ALONG THE NEB/SD BORDER DURING THE EVENING WITH A COUPLE
TORNADOES POSSIBLE.
THERE MAY BE ISOLD TSTM DEVELOPMENT ALONG THE RETREATING WARM FRONT
ACROSS NRN/CNTRL MO AND SERN NEB SUNDAY AFTERNOON. MODELS MAY BE
OVERESTIMATING EVAPOTRANSPIRATION AND CONTRIBUTING TO WEAKER CINH
AND QPF. THE UNCERTAINTY WILL PRECLUDE A SLGT RISK...BUT WILL COVER
THE POSSIBILITY FOR SVR STORMS WITH LOW SVR PROBABILITIES ATTM.
SOME UNCERTAINTY EXISTS ON OVERNIGHT EVOLUTION OF ACTIVITY. SOME
MODELS HINT THAT STORMS WILL EVENTUALLY CONGEAL AND/OR DEVELOP ALONG
THE EDGE OF CAP FROM NERN NEB/SERN SD INTO PARTS OF IA BY 12Z
MONDAY. IF THIS WERE TO OCCUR...MOST OF THE STORMS WILL LIKELY BE
ELEVATED WITH AT LEAST ISOLD LARGE HAIL A DISTINCT POSSIBILITY.
...SRN PLAINS...
CONDITIONAL THREAT FOR ISOLD SUPERCELL STORMS WILL EXIST MID-AFTN
SUNDAY INTO THE MID-EVENING HOURS. MODELS CONTINUE TO INDICATE THAT
A WEAK TROUGH/HEIGHT FALLS WILL GRAZE THE REGION DURING PEAK
HEATING. FCST TEMPERATURES WILL BE IN EXCESS OF 100 DEG F WEST OF
THE DRYLINE AND THERE MAY BE A SUFFICIENTLY DEEP CIRCULATION ALONG
THE BOUNDARY FOR WEAKENING CINH/ISOLD TSTM INITIATION ACROSS WRN
OK/NW TX. ROUGHLY 50 KTS OF CROSS-BOUNDARY DEEP-LAYER SHEAR AND
VERY STEEP MID-LEVEL LAPSE RATES WILL BE FAVORABLE FOR VERY LARGE
HAIL WITH ANY STORM THAT CAN FORM. A TORNADO CANNOT BE RULED OUT
EARLY IN THE EVENING...BUT LCL/S WILL BE SOMEWHAT HIGH. THE ZONE OF
SVR THREAT WILL BE NARROW SINCE ANY SUSTAINED STORM WILL MOVE INTO
AN INCREASINGLY CAPPED ENVIRONMENT OVER NCNTRL TX/CNTRL OK DURING
THE LATE EVENING.
MORE UNCERTAINTY EXISTS FOR CONVECTIVE INITIATION ELSEWHERE ALONG
THE DRYLINE FROM CNTRL KS TO THE E PARTS OF THE EDWARDS PLATEAU
WHERE CAP WILL REMAIN VERY STRONG.
...SERN STATES...
LOW-LEVEL MOISTURE CIRCULATING ALONG WRN/NRN FRINGE OF THE
SUBTROPICAL HIGH WILL CONTRIBUTE TO A RIBBON OF 1000-1500 J/KG
MLCAPE FROM THE SRN APPALACHIANS SEWD TO SC SUNDAY AFTERNOON. MASS
CONVERGENCE ALONG THE SWD MOVING COLD FRONT WILL INSTIGATE SCATTERED
TSTMS SUNDAY AFTERNOON/EARLY EVENING. MODEST WNWLY...
UNIDIRECTIONAL FLOW REGIME WILL COUPLE WITH RELATIVELY DRY SUB-CLOUD
LAYER TO YIELD STRONG MULTICELL STORMS WITH POSSIBLE DMGG
WINDS/HAIL.
..RACY.. 05/07/2011
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