SWODY3
SPC AC 200728
DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0228 AM CDT WED OCT 20 2010
VALID 221200Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL/SRN PLAINS...
...SYNOPSIS...
BREAKDOWN OF WRN CONUS REX PATTERN...DESCRIBED IN DAY-2
OUTLOOK...WILL LEAD TO NEWD EJECTION OF MID-UPPER LOW AND
ACCOMPANYING/NEGATIVELY-TILTED SHORTWAVE TROUGH ACROSS SRN/CENTRAL
HIGH PLAINS THIS PERIOD. BY 23/12Z...CONSIDERABLE SPREAD IS EVIDENT
IN SREF PROGS AND OPERATIONAL SPECTRAL/WRF REGARDING POSITION OF
500-MB LOW OR VORTICITY CENTER...WITH INCONSISTENCIES ALSO REGARDING
CLOSURE/OPENNESS OF SHORTWAVE TROUGH AND POSITION/DEPTH OF RESULTING
SFC CYCLONE. AS PRIMARY VORTICITY LOBE MOVES NEWD OUT OF NM AND
OVER WRN KS...INITIAL LEE-SIDE LOW OVER SERN CO WILL INTENSIFY AND
MOVE NEWD AS WELL...BUT WITH STRENGTH/TRACK RATHER UNCERTAIN ATTM
BEYOND ABOUT 22/18Z. SFC FRONTAL/CONVERGENCE ZONE SHOULD MOVE EWD
ACROSS PANHANDLES AND W TX...BUT NOT AS FAST AS DAY-2/EARLY DAY3
CONVECTION...RESULTING IN POTENTIAL FOCUS FOR AFTERNOON DEVELOPMENT
OVER PORTIONS SW KS AND TX/OK PANHANDLES INTO WRN OK AND NW TX.
...CENTRAL/SRN PLAINS...
BANDS/CLUSTERS OF TSTMS SHOULD CARRY OVER FROM DAY-2 PERIOD ACROSS
PORTIONS SRN KS...OK AND PERHAPS NW TX...WITH SVR POTENTIAL EXPECTED
TO BE MRGL DURING EARLY-MORNING MIN IN BOUNDARY-LAYER INSTABILITY.
THIS ACTIVITY SHOULD MOVE NEWD ACROSS KS/OK AND WEAKEN...LEAVING
BEHIND TEMPORARILY STABILIZED AIR MASS WITH SFC DEW POINTS GENERALLY
50S F. DEVELOPMENT OF AT LEAST ISOLATED TO WIDELY SCATTERED TSTMS
IS EXPECTED DURING AFTERNOON INVOF CONVERGENCE ZONE. CAPPING IS NOT
EXPECTED TO BE PARTICULARLY STG OVER ANY AREAS FROM NW TX TO SRN KS
THAT EXPERIENCE A FEW HOURS OF SUSTAINED SFC HEATING.
THEREFORE...FOR ANY CONVECTION THAT DOES DEVELOP...CONDITIONAL BUT
POTENTIALLY MULTI-MODAL SEVERE RISK IS APPARENT. BELT OF 40-60 KT
500 MB WSWLYS IS POSSIBLE SE OF UPPER LOW/TROUGH OVER OUTLOOK
AREA...CONTRIBUTING TO ENHANCED DEEP-LAYER SHEAR...WITH SUBSTANTIAL
COMPONENT OF FLOW ACROSS PROSPECTIVE FOCI FOR TSTM GENESIS.
FAVORABLY LARGE HODOGRAPHS AND 40-50 KT EFFECTIVE SHEAR MAGNITUDES
ARE EVIDENT IN FCST SOUNDINGS...SUPPORTING SUPERCELL RISK WITH
HAIL/SVR GUSTS/TORNADOES POSSIBLE.
ATTM...MAIN UNCERTAINTIES INVOLVE
1. AMOUNT OF DESTABILIZATION THAT CAN OCCUR BEHIND EARLY CONVECTION
AND RELATED CLOUD COVER OVER NRN PART OF AREA FROM WRN/SRN KS TO NW
TX...AND
2. SRN LIMIT OF CONVECTIVE DEVELOPMENT ACROSS NW/W-CENTRAL TX. WITH
SWD EXTENT...EXPECT DECREASES IN DEEP-LAYER SHEAR...LOW-LEVEL
HODOGRAPH SIZE...LOW-LEVEL CONVERGENCE AND MID-UPPER LEVEL FORCING
FOR ASCENT...WHILE CAPPING INCREASES.
..EDWARDS.. 10/20/2010
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