DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 130534
SWODY1
SPC AC 130532

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1232 AM CDT SAT OCT 13 2012

VALID 131200Z - 141200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS SRN/CENTRAL PLAINS TO
PORTIONS UPPER MS VALLEY REGION...

...SYNOPSIS...
SPLIT-FLOW PATTERN NOW OVER WRN CONUS IS FCST TO DEAMPLIFY THROUGH
PERIOD. WELL-DEFINED MID-UPPER LEVEL CYCLONE -- INITIALLY OVER ERN
UT/WRN CO REGION -- IS FCST TO MOVE ENEWD ACROSS CO BY START OF
PERIOD...DEVOLVING TO OPEN-WAVE TROUGH AS IT CROSSES CENTRAL PLAINS.
BY 14/00Z...EXPECT HIGH-AMPLITUDE SHORTWAVE TROUGH WITH SLGT
POSITIVE TILT...FROM S-CENTRAL/SERN NEB ACROSS WRN KS...TX
PANHANDLE...AND TX SOUTH-PLAINS REGION. THIS PERTURBATION WILL
BECOME MORE NEUTRALLY TILTED WITH TIME THEREAFTER...BUT ALSO...WILL
LINK WITH NRN-STREAM FLOW BELT AND DEAMPLIFY. TROUGH SHOULD BE
CROSSING WRN OZARKS...WRN MO...AND IA BY 14/12Z.

AT SFC...PAC COLD FRONT IS FCST TO MOVE EWD OUT OF ROCKIES...WITH
ATTACHED FRONTAL-WAVE LOW OVER ERN NEB/WRN IA REGION BY 14/00Z...AND
FRONT SWWD ACROSS N-CENTRAL KS...NWRN OK AND TRANS-PECOS AREA OF W
TX. BY LATE AFTERNOON...DRYLINE SHOULD INTERSECT PAC FRONT
OBLIQUELY OVER NWRN OR WRN OK...AND EXTEND SSWWD ACROSS NW TX AND
PERMIAN BASIN REGION. DRYLINE AND PAC FRONT SHOULD MERGE THROUGH
REMAINDER PERIOD. MEANWHILE...DIFFUSE WARM FRONT -- NOW LOCATED
OVER PORTIONS CENTRAL/SRN OK AND SRN AR -- IS FCST TO MOVE OR
REDEVELOP NWD RAPIDLY ACROSS LOWER MO VALLEY REGION EARLY IN PERIOD.
WARM FRONT SHOULD EXTEND FROM SFC LOW ACROSS NRN IA AND SRN WI BY
14/00Z. BY END OF PERIOD...EXPECT PRIMARY SFC LOW OVER NWRN IL/SWRN
WI REGION...WITH WARM FRONT ENEWD OVER LOWER MI...AND COLD FRONT
OVER NRN/WRN MO...ERN OK...AND W-CENTRAL TX.

...PORTIONS SRN/CENTRAL PLAINS...
BAND OF TSTMS SHOULD BE ONGOING AT START OF PERIOD FROM PORTIONS
W-CENTRAL TX NNEWD ACROSS NW TX AND WRN OK...INTO PORTIONS CENTRAL
KS AND PERHAPS FARTHER NE. RELATED ANVIL SHIELD WILL SUBDUE PACE OF
INSOLATION IN ITS INFLOW REGION. HOWEVER...COMBINATION OF SLOW SFC
HEATING AND BOUNDARY-LAYER THETAE ADVECTION SHOULD YIELD FAVORABLY
LARGE BUOYANCY TO SUPPORT GROWING SVR THREAT WITH TIME THROUGHOUT
DAYLIGHT HOURS...AS BAND MOVES EWD ACROSS OUTLOOK AREA.
BACKBUILDING WITH TIME ALSO IS POSSIBLE ACROSS PORTIONS W-CENTRAL/SW
TX ALONG/AHEAD OF DRYLINE...PERHAPS AS FAR S AS RIO GRANDE.
FURTHERMORE...SOME PROGS SUGGEST MID-LATE AFTERNOON QUASI-LINEAR
TSTM DEVELOPMENT BEHIND INITIAL ACTIVITY AND ALONG/AHEAD OF COLD
FRONT OVER PORTIONS KS/NWRN OK. WIDTH AND MAGNITUDE OF ANY
DESTABILIZATION CORRIDOR BEHIND INITIAL/PRIMARY TSTM BAND IS QUITE
QUESTIONABLE ATTM...THOUGH THIS AREA GENERALLY IS COVERED BY
UNCONDITIONAL...MRGL TO SLGT-RISK LEVEL PROBABILITIES THAT ALREADY
ACCOUNT FOR EARLIER TSTMS.

PRIMARY THREAT FROM ANY OF THE ABOVE CONVECTION WILL BE DAMAGING
GUSTS...WITH QUASI-LINEAR MODES DOMINANT FOR MOST OF PERIOD.
NONETHELESS...FAVORABLE DEEP SHEAR AND POTENTIAL FOR AT LEAST A FEW
SUPERCELLS SUGGESTS CATEGORICAL HAIL RISK. ANY SUCH
SUPERCELLS...ALONG WITH EMBEDDED QLCS CIRCULATIONS...COLLECTIVELY
OFFER RELATIVELY MAXIMIZED TORNADO POTENTIAL AT LEAST BETWEEN NW TX
AND WRN MO...WHERE ENLARGED LOW-LEVEL HODOGRAPHS ARE MOST LIKELY TO
JUXTAPOSE WITH FAVORABLE DESTABILIZATION. TORNADO THREAT FARTHER NE
AND SW...WHILE NONZERO...IS MORE CONDITIONAL.

OVERALL SVR POTENTIAL SHOULD DIMINISH FROM LATE EVENING ONWARD OVER
MOST OF THIS AREA AS BOUNDARY LAYER SLOWLY STABILIZES...AND AS
PRIMARY MID-UPPER WAVE DEAMPLIFIES. THREAT MAY PERSIST LONGEST
OVERNIGHT ACROSS PORTIONS S TX INTO N-CENTRAL/NE TX AND SERN
OK...WHERE LOW-LEVEL THETAE WILL REMAIN HIGHEST IN ABSENCE OF
SUBSTANTIAL CAPPING.

...NRN MO/ERN NEB TO SWRN WI...NWRN IL...
SCATTERED TSTMS MAY MOVE NEWD ACROSS THIS REGION EARLY IN
PERIOD...PERHAPS AS EXTENSION OF ACTIVITY NOW CROSSING PORTIONS
CENTRAL/SRN HIGH PLAINS. SOME ACTIVITY MAY PERSIST OR REDEVELOP
INTO AFTERNOON HOURS WHEN BOUNDARY-LAYER THETAE ADVECTION COULD
INTRODUCE SFC-BASED PARCELS TO CONVECTIVE INFLOW REGION.
SEPARATE/NNE-SSW ALIGNED BELT OF TSTMS ALSO MAY DEVELOP AHEAD OF SFC
COLD FRONT OVER PORTIONS MO/IA AND SHIFT EWD.

AFTERNOON/EVENING WIND PROFILES WILL BE FAVORABLE FOR SVR OVER WARM
SECTOR IN THIS REGION...ALBEIT EXHIBITING SOME BACKING WITH HEIGHT
IN MIDLEVELS COMMON TO QUASI-LINEAR EVENTS. FCST SOUNDINGS SUGGEST
35-45 KT EFFECTIVE SHEAR...ALONG WITH ENHANCED LOW-LEVEL HODOGRAPHS
INVOF WARM FRONT AND SFC LOW. MOST PROGS ALSO INDICATE SOME DEGREE
OF SUFFICIENT SFC-BASED DESTABILIZATION ACROSS THIS REGION...E.G.
1000-1500 J/KG MLCAPE PREDICTED BY NAM. HOWEVER...SUBSTANTIAL
DESTABILIZATION MAY BE PRECLUDED BY PRECURSORY PRECIP AND CLOUD
COVER MOVING INTO THIS REGION FROM UPSHEAR AREAS OF CENTRAL PLAINS
DURING MORNING/EARLY AFTERNOON HOURS. WHILE CORRIDOR OF RELATIVELY
ENHANCED SVR WIND POTENTIAL YET MAY DEVELOP POLEWARD OF PRESENT 30%
LINE...EXTENT/TIMING REMAINS TOO UNCERTAIN TO EXTEND THAT
PROBABILITY FARTHER NNE ATTM.

..EDWARDS/ROGERS.. 10/13/2012

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