DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 120538
SWODY1
SPC AC 120535

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1235 AM CDT FRI OCT 12 2012

VALID 121200Z - 131200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS WRN KS TO SRN HIGH
PLAINS...

...SYNOPSIS...
SPLIT-FLOW PATTERN IN MID-UPPER LEVELS IS EXPECTED TO DEAMPLIFY
SOMEWHAT DURING PERIOD...OVER WRN CONUS. THIS WILL OCCUR AS
WELL-DEFINED CYCLONE -- NOW LOCATED OVER SRN CA -- MOVES ENEWD FROM
SERN SIERRA REGION. THOUGH THIS CYCLONE IS FCST TO FILL
GRADUALLY...IT WILL MAINTAIN HIGH-AMPLITUDE SHORTWAVE TROUGH WITH
POSITIVE TILT AS IT EJECTS FROM ITS MOST EQUATORWARD POSITION...AND
REJOINS PREVAILING WLYS ALOFT. PRIMARY 500-MB VORTICITY LOBE SHOULD
MOVE NEWD ACROSS UT DURING MIDDLE OF PERIOD...EXTENDING FROM WRN NEB
TO S-CENTRAL CO AND WRN NM BY 13/12Z.

AT SFC...COLD FRONT WAS ANALYZED FROM SERN ONT SWWD ACROSS NRN/WRN
IL AND S-CENTRAL KS TO NRN PORTIONS TX PANHANDLE. WRN PORTION OF
THIS FRONT IS PROGGED TO STALL ACROSS PANHANDLE AND NERN NM EARLY IN
PERIOD...THEN RETURN NWD AS WARM FRONT OVER NRN OK...OK/NRN TX
PANHANDLES AND SERN CO. HOWEVER...PRECEDING/MORNING CONVECTION MAY
EFFECTIVELY SHUNT FRONT SWD SOMEWHAT OVER OK...TX PANHANDLE AND NERN
NM...DELAYING ITS NWD MOVEMENT THROUGH DAYLIGHT HOURS. DRYLINE
SHOULD SET UP OVER ERN NM DURING MID-LATE AFTERNOON...AND DEVELOP
NWD ACROSS SERN CO/SWRN KS AREA OVERNIGHT AS MORNING CONVECTIVE AIR
MASS DISSIPATES AND FRONT PROCEEDS NWD OVER WRN/SRN/CENTRAL KS.

...WRN KS TO SRN HIGH PLAINS...
TSTMS ARE FCST TO DEVELOP DIURNALLY ACROSS PORTIONS ERN NM ALONG AND
E OF DRYLINE AND OVER HIGHER TERRAIN. REGIONAL TSTM INITIATION MAY
COMMENCE AS EARLY AS 18Z-20Z TIME FRAME GIVEN FCST OF RELATIVELY
WEAK MLCINH...AND TIME SERIES OF FCST SOUNDINGS SUGGESTING REMOVAL
OF CINH FOR SFC TEMPS MID-70S F IN SOME AREAS AWAY FROM MOUNTAINS.
COMPLICATING FACTOR WILL BE PRESENCE OF MID-UPPER LEVEL
CLOUDS...BASED ON CURRENT/UPSTREAM SATELLITE TRENDS AND PROGS OF
HIGH RH ALOFT. THIS FACTOR ALSO MAY DELAY OR GRADATE TSTM
INITIATION PROCESSES...DEPENDING ON MESOSCALE CHARACTER OF CLOUD
COVER.

BY LATE AFTERNOON...CONVECTIVE COVERAGE/INTENSITY SHOULD BE
INCREASING ACROSS TX/NM BORDER REGION. LOW-LEVEL MOISTURE AND
STRENGTHENING DEEP SHEAR ALONG/AHEAD OF DRYLINE WILL SUPPORT MORE
ORGANIZED SVR POTENTIAL..INCLUDING RISK OF SUPERCELLS WITH LARGE
HAIL AND DAMAGING GUSTS...AS WELL AS POTENTIAL FOR SVR CLUSTERED OR
BOWING STORM MODES. FOR THOSE CELLS THAT STILL ARE RELATIVELY
DISCRETE DURING 00Z-03Z TIME FRAME...TORNADO POTENTIAL MAY INCREASE.
THIS WOULD BE DURING TEMPORAL OVERLAP OF TWO PROCESSES...
1. STRENGTHENING LLJ THAT FAVORABLY ENLARGES LOW-LEVEL
HODOGRAPH...BOOSTING EFFECTIVE SRH VALUES PAST 200 J/KG...AND
2. PRECONVECTIVE/EFFECTIVE LIFTED PARCELS S OF WARM FRONT AND E OF
DRYLINE REMAINING SFC-BASED...EVEN WITH VERY SHALLOW LAYER OF
EARLY-STAGE DIABATIC COOLING.

UPSCALE GROWTH OF NNE-SSW ALIGNED CONVECTIVE BAND SHOULD OCCUR
DURING EVENING AND OVERNIGHT HOURS -- 03Z-09Z TIME FRAME -- WITH
CONVECTION SHIFTING EWD AND PERHAPS GROWING NEWD INTO ENLARGING KS
WARM SECTOR. SPORADIC LARGE HAIL AND DAMAGING GUSTS WILL BE MAIN
CONCERNS AFTER ABOUT 06Z...WITH SVR THREAT DIMINISHING TOWARD
NOCTURNAL INSTABILITY MIN NEAR END OF PERIOD.

...S-CENTRAL ROCKIES...
POTENTIAL FOR ISOLATED HAIL/GUSTS NEAR SVR LIMITS MAY EXTEND NWWD
FROM MAIN SVR RISK AREA ACROSS MOUNTAINS AND ADJOINING BASINS OF NRN
NM AND SRN CO. MOISTURE/BUOYANCY WILL BE SUBSTANTIALLY MORE LIMITED
IN THIS REGION THAN FARTHER E. HOWEVER...STRENGTHENING DEEP-LAYER
ASCENT/SHEAR WITH TIME WILL SUPPORT MRGL/CONDITIONAL SVR THREAT
PRIMARILY WITH MID-LATE AFTERNOON CONVECTION OVER THIS REGION.

...CENTRAL PLAINS N OF I-70 TO PORTIONS SRN MN/IA...
LOW-LEVEL WAA AND MOISTURE ADVECTION/TRANSPORT REGIME WILL SPREAD
NEWD RAPIDLY ACROSS CENTRAL PLAINS INTO MID MO VALLEY REGION
OVERNIGHT...SUPPORTING LIKEWISE SHIFT IN ELEVATED THETAE LAYER
SUPPORTING MUCAPE 1000-1500 J/KG. FCST SOUNDINGS SUGGEST EFFECTIVE
SHEAR MAGNITUDES IN 35-45 KT RANGE ARE POSSIBLE...SUPPORTING A FEW
SPORADICALLY WELL-ORGANIZED TSTMS WITH HAIL NEAR SVR LEVELS.

..EDWARDS/DEAN.. 10/12/2012

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