SWODY2
SPC AC 210600
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT THU OCT 21 2010
VALID 221200Z - 231200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS CENTRAL/SRN PLAINS...
...SYNOPSIS...
MID-UPPER LEVELS CURRENTLY FEATURE WRN CONUS REX PATTERN...WITH
ANTICYCLONE OVER ID AND CUT-OFF CYCLONE OVER LOWER CO RIVER
VALLEY/SWRN AZ. HEIGHT FALLS...AHEAD OF STG NERN PAC SHORTWAVE
TROUGH NOW NEAR 135W...WILL CONTRIBUTE TO BREAKING DOWN REX PATTERN
AND SHIFTING BOTH CYCLONE AND RIDGING ACROSS ROCKIES. BY
22/12Z...500-MB CYCLONE SHOULD BE LOCATED OVER NERN NM...BASED ON
STG CONSENSUS OF SREF AND DETERMINISTIC PROGS. THIS LOW SHOULD MOVE
NEWD TO WRN/CENTRAL NEB BY END OF PERIOD.
AT SFC...LOW SHOULD DEVELOP BY EARLY IN PERIOD OVER SERN CO...WITH
TROUGH EXTENDING NWWD TO ANOTHER WEAK LOW OVER WY. SRN LOW SHOULD
MOVE NEWD WITH UPPER CYCLONE AND STRENGTHEN OVERNIGHT...RESULTING IN
WELL-DEFINED SFC CYCLONE OVER NWRN KS/SWRN NEB AREA BY 23/12Z.
COMBINED DRYLINE/PAC FRONT SHOULD EXTEND SSEWD/SWD FROM MAIN SFC
LOW...WHILE MOVING EWD ACROSS W TX AND PANHANDLES DURING DAY. STG
ANTICYCLONE WILL SHIFT SEWD FROM OH VALLEY ACROSS CAROLINAS...WITH
PRONOUNCED RIDGING SWWD ACROSS CENTRAL GULF. RELATED TRAJECTORIES
WILL KEEP MOISTURE RETURN PLUME SOMEWHAT NARROW IN ZONAL EXTENT OVER
SRN/CENTRAL PLAINS...BUT STILL SUFFICIENT TO SUPPORT SVR POTENTIAL
THIS PERIOD.
...CENTRAL/SRN PLAINS...
SCATTERED-NUMEROUS TSTMS SHOULD BE ONGOING AT 22/12Z OVER PORTIONS
OK AND PERHAPS NW TX...WITH MRGL SVR POTENTIAL FOR GUSTS/HAIL. THIS
ACTIVITY SHOULD MOVE NEWD ACROSS OK/SRN KS DURING REMAINDER MORNING
HOURS AND WEAKEN AS SUPPORTIVE LLJ LIKEWISE DIMINISHES. MAIN SVR
THREAT SHOULD BEGIN DURING AFTERNOON ALONG/AHEAD OF DRYLINE/FRONT IN
ARC FROM PORTIONS CENTRAL/SW TX ACROSS OK TO WRN KS...AS SECOND
ROUND OF SCATTERED-NUMEROUS TSTMS FORMS AND MOVES NEWD. TWO
DISTINCT NODES OF CONVECTION ARE EVIDENT--
1. NEAR SFC AND UPPER LOWS OVER SERN CO/WRN KS...AND
2. ALONG/AHEAD OF DRYLINE/FRONT OVER PORTIONS CENTRAL/SW TX INTO
WRN/CENTRAL OK AND PERHAPS SRN KS.
RELATIVE MIN MAY EXIST BETWEEN THESE TWO REGIMES...BUT DEPENDENT ON
MESOSCALE FACTORS THAT ARE TOO UNCERTAIN TO DEPICT PROBABILISTIC MIN
ATTM.
DEEP-LAYER SHEAR IS FCST TO BE FAVORABLE FOR SUPERCELLS/BOWS OVER
MOST OF CORRIDOR FROM SWRN/S-CENTRAL KS TO CENTRAL TX...BENEATH
BROAD SWATH OF 45-55 KT 500 MB FLOW. LEFT-EXIT REGION OF 100-110 KT
250 MB JET MAX -- CENTERED FROM W-CENTRAL TX SWWD ACROSS
CHIHUAHUA...ALSO WILL SPREAD OVER AREA FROM SRN KS TO NW TX BY
23/00Z. SFC WINDS ARE FCST TO BE SOMEWHAT MORE BACKED WITH EWD
EXTENT AWAY FROM DRYLINE/FRONT...AND ALSO...WITH NWD EXTENT ACROSS N
TX INTO OK IN PROXIMITY TO MODIFYING POST-CONVECTIVE AIR MASS.
THEREFORE...LOW-LEVEL SHEAR WILL BE MOST FAVORABLE FOR ANY
RELATIVELY DISCRETE/SUSTAINED ACTIVITY THAT DEVELOPS ON DRYLINE AND
MOVES WELL EWD INTO LARGER HODOGRAPHS...OR TSTMS THAT FORM IN WHAT
MAY BE WEAKLY CAPPED MOIST SECTOR.
THIS PATTERN IS NOT CONDUCIVE TO WELL-DEVELOPED/ANTECEDENT ELEVATED
MIXED LAYER...WITH COLD AIR ALOFT AND ABUNDANT PRECIP/CONVECTION
OCCURRING NOW ACROSS NM. THEREFORE...LAPSE RATES ALOFT WILL NOT BE
AS STEEP AS WITH MANY SPRINGTIME SYSTEMS...EXCEPT UNDER IMMEDIATE
COLD-CORE AREA OF MID-UPPER CYCLONE. STILL...LOW-LEVEL MOISTURE
SHOULD BE SUFFICIENT TO SUPPORT SVR...WITH DEW POINTS 50S F NEAR
COLD-CORE REGION OF LOW ALOFT...TO 60S OVER N TX AND SRN/CENTRAL OK.
STRENGTH/DURATION OF DIABATIC SFC HEATING IS MORE UNCERTAIN WITH
NEWD EXTENT ACROSS OK/KS...GIVEN LIKELIHOOD OF STABILIZATION/CLOUDS
FROM MORNING TSTMS. STILL...AT LEAST NARROW CORRIDOR OF RECOVERY IS
EXPECTED AHEAD OF DRYLINE/FRONT AND WITHIN WRN FRINGES OF MOIST
SECTOR OVER KS/OK...SUPPORTING MLCAPE RANGING FROM 200-700 J/KG OVER
NARROW AREAS OF SWRN KS/NWRN/N-CENTRAL OK TO AROUND 1000 J/KG OVER
PORTIONS OK TO ROUGHLY 2000 J/KG OVER SW TX. BECAUSE OF WEAK
CAPPING RELATE TO LACK OF ROBUST EML...TSTMS MAY DEVELOP RATHER
EARLY IN AFTERNOON AS WELL.
IN MOIST SECTOR...MAIN CONCERNS INVOLVE TIMING/MODE OF CONVECTION
AND SPECIFIC/MESOSCALE LOCATION OF THAT TRANSITION ZONE FROM
UNDISTURBED WARM SECTOR TO THAT PART OF CONVECTIVELY MODIFIED AIR
TOO STABLE FOR SFC-BASED SVR. THAT REGIME WILL CONSIST OF
REGIONALLY MAXIMIZED SUPERCELL/TORNADO POTENTIAL GIVEN LIKELIHOOD OF
BACKED FLOW...HIGHER SRH/VORTICITY IN LOW LEVELS...AND LOWER LCL
THAN IN BETTER MIXED/HEATED AIR MASS FARTHER S. SECOND RELATIVE MAX
IN DIURNAL TORNADO POTENTIAL MAY EXIST IN HIGH-VORTICITY AIR MASS
BENEATH MID-UPPER LOW...NEAR SFC FRONT/TROUGH.
..EDWARDS.. 10/21/2010
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