DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 131254
SWODY1
SPC AC 131252

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0752 AM CDT SAT OCT 13 2012

VALID 131300Z - 141200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE MIDWEST
AND MID MO VALLEY TO THE LOWER RIO GRANDE VALLEY...

...SYNOPSIS...

THE PRIMARY FEATURES OF INTEREST THIS PERIOD ARE A SIGNIFICANT
VORTICITY MAXIMUM AND ASSOCIATED MIDLEVEL JET STREAK /12Z ABQ
SOUNDING SAMPLED 90-95 KT WINDS JUST ABOVE 500 MB/ WHICH WILL
PROGRESS FROM THE SRN ROCKIES INTO WRN PARTS OF TX/OK BY 14/00Z
BEFORE REACHING THE OZARKS BY 14/12Z. THE PROGRESSION OF THIS
VORTICITY MAXIMUM WILL CONTRIBUTE TO THE INTENSIFICATION AND
CONCOMITANT TRANSITION FROM A POSITIVE TO NEUTRAL TILT OF
BROADER-SCALE TROUGH TRANSLATING THROUGH THE CNTRL/SRN PLAINS TOWARD
THE MID MS VALLEY.

IN THE LOW LEVELS...THE PRIMARY SURFACE CYCLONE INITIALLY OVER THE
CNTRL DAKOTAS WILL DEVELOP SWD INTO S-CNTRL NEB/N-CNTRL KS BY 14/00Z
BEFORE SHIFTING NEWD INTO E-CNTRL IA BY 14/12Z. THIS LOW PRESSURE
CENTER WILL BE ACCOMPANIED BY A PACIFIC FRONT WHICH IS FORECAST TO
EXTEND SSWWD THROUGH CNTRL KS/WRN OK INTO W-CNTRL AND SWRN TX BY
LATE AFTERNOON/EARLY EVENING...BEFORE ADVANCING EWD INTO THE OZARK
PLATEAU AND CNTRL TX BY SUNDAY MORNING. MEANWHILE...A WARM FRONT
FRONT...PRECEDING THE MAIN SURFACE LOW...WILL PROGRESS NEWD THROUGH
THE LOWER MO VALLEY.

...CNTRL KS INTO WRN MO AND SWD INTO NRN TX TODAY INTO TONIGHT...

AN APPARENT LOW-LATITUDE...LOW-AMPLITUDE IMPULSE OVER W-CNTRL TX IS
CONTRIBUTING TO A RECENT INCREASE IN ELEVATED CONVECTION FROM THE
ERN TX PNHDL INTO THE TX BIG COUNTRY AND CONCHO VALLEY. AND IT
APPEARS THAT THE INFLUENCE OF THIS PERTURBATION MAY BE RESPONSIBLE
FOR THE EARLY ONSET OF STORM DEVELOPMENT ACROSS PORTIONS OF OK AND N
TX AS DEPICTED BY VARIOUS CONVECTION-ALLOWING AND MESOSCALE MODELS.
THE EXTENT TO WHICH THIS EARLY DAY CONVECTION DEVELOPS REMAINS
UNCERTAIN...THOUGH MORE WIDESPREAD STORMS COULD HAVE A
SUBSTANTIAL...NEGATIVE IMPACT ON SUBSEQUENT STORM FORMATION LATER
TODAY ALONG THE PACIFIC FRONT/DRYLINE. MOREOVER...DOMINANT
CONVECTIVE MODE WITH THE DIURNALLY ENHANCED STORMS THIS AFTERNOON
REMAINS UNCLEAR...FURTHER BREEDING UNCERTAINTY INTO THE FORECAST.

BASED ON THE 12Z OUN SOUNDING...IT APPEARS THAT ANY EARLY DAY
CONVECTION WILL LIKELY BE ELEVATED IN NATURE AND BASED AROUND 700
MB. HAIL APPROACHING SEVERE LEVELS WOULD BE THE PRIMARY HAZARD WITH
THIS ACTIVITY. AS MENTIONED ABOVE...A POTENTIALLY MORE SIGNIFICANT
SEVERE WEATHER THREAT WILL LARGELY BE MODULATED BY THE DEGREE OF
ELEVATED STORMS THAT DEVELOP THIS MORNING. THERE IS A HIGH
CERTAINTY THAT STORM INITIATION WILL OCCUR ALONG THE DRYLINE/PACIFIC
FRONT BY MID/LATE AFTERNOON FROM WRN OK INTO NWRN TX AS THE
VORTICITY MAXIMUM AND ASSOCIATED JET STREAK MOVE INTO THE SRN HIGH
PLAINS. THE NRN BOUND OF THIS CONVECTIVE DEVELOPMENT WILL BE
DICTATED BY DEGREE TO WHICH THE AIR MASS CAN RECOVER INTO KS.

MULTIPLE CONVECTIVE MODES ARE POSSIBLE...INCLUDING SUPERCELLS AND
LINE SEGMENTS WITH AN ASSOCIATED RISK FOR LARGE HAIL...DAMAGING
WINDS...AND TORNADOES. SUBSEQUENT UPSCALE GROWTH INTO A QLCS IS
ANTICIPATED WITH A DAMAGING WIND AND POSSIBLE TORNADO THREAT
SPREADING EWD INTO WRN PORTIONS OF THE OZARK PLATEAU THIS EVENING
INTO TONIGHT.

SHOULD EARLY DAY STORM COVERAGE REMAIN RELATIVELY ISOLATED WITH
LITTLE IMPACT ON THE WARM SECTOR...FORECAST SOUNDINGS OVER CNTRL OK
VALID LATE THIS AFTERNOON INTO EVENING INDICATE THE POTENTIAL FOR A
GREATER SUPERCELL/TORNADO THREAT THAN IS INDICATED BY CURRENT
TORNADO AND HAIL PROBABILITIES. TRENDS WILL CLOSELY BE MONITORED
FOR A POSSIBLE UPGRADE IN PROBABILITIES IN SUBSEQUENT OUTLOOKS.

...CNTRL/SWRN TX THIS AFTERNOON INTO TONIGHT...

SATELLITE-DERIVED PW IMAGERY AND 12Z OBSERVED SOUNDINGS SHOW THE
PRESENCE OF A RATHER MOIST AIR MASS...CHARACTERIZED BY BOUNDARY
LAYER DEWPOINTS IN THE MID 60S TO LOWER 70S AND PW VALUES OF 1.5-2.0
INCHES. THIS MOISTURE WILL ALIGN WITH MODESTLY STEEP MIDLEVEL LAPSE
RATES AND DECREASING CLOUDS TO YIELD A MODERATELY UNSTABLE AIR MASS
BY AFTERNOON WITH MLCAPE VALUES APPROACHING 1500-2500 J/KG.
SURFACE-BASED STORM INITIATION IS ANTICIPATED BY MID/LATE AFTERNOON
ALONG THE DRYLINE/PACIFIC FRONT FROM W-CNTRL TX INTO WRN PORTIONS OF
THE EDWARDS PLATEAU AS WELL AS THE HIGH TERRAIN OF NWRN MEXICO AS
REGION IS GLANCED BY STRONGER HEIGHT FALLS/FORCING FOR ASCENT
PASSING TO THE NORTH.

FORECAST HODOGRAPHS EXHIBIT VERTICALLY VEERING WIND PROFILES WITH
DEEP...WLY SHEAR STRENGTHENING TO 40-50 KT. AS SUCH...THE POTENTIAL
WILL EXIST FOR SUPERCELLS CAPABLE OF LARGE HAIL AND DAMAGING WIND
GUSTS. THE THREAT FOR AT LEAST ISOLATED SEVERE WEATHER WILL
CONTINUE INTO TONIGHT AS STORMS COALESCE INTO CLUSTERS OR AN MCS.

...MID/LOWER MO VALLEY THIS AFTERNOON AND EVENING...

WIDESPREAD CONVECTION ONGOING FROM KS INTO IA IN
ASSOCIATION WITH ASCENT LEADING THE LARGE-SCALE TROUGH WILL CONTINUE
TO SHIFT EWD/NEWD THROUGH THE DAY. IN THE WAKE OF THIS
ACTIVITY...THE INFLUX OF A WARM/MOIST BOUNDARY LAYER FROM THE
CNTRL/SRN PLAINS BENEATH STEEPENING MID-LEVEL LAPSE RATES SHOULD
PROMOTE AT LEAST MARGINAL DESTABILIZATION BY LATE AFTERNOON TO THE
SOUTH OF A NWD-ADVANCING WARM FRONT. THE PRESENCE OF 35-50 KT OF
500-MB FLOW WILL SUPPORT SUFFICIENT DEEP SHEAR FOR ORGANIZED STORM
STRUCTURES INCLUDING SUPERCELLS WITHIN A BROAD AREA OF CONVECTION
THAT WILL LIKELY MATERIALIZE LATE THIS AFTERNOON AND PERSIST INTO
TONIGHT...AS STRONGER MID-LEVEL HEIGHT FALLS/ASCENT APPROACH. WHILE
THERE IS SOME UNCERTAINTY WITH REGARD TO THE MAGNITUDE OF
DESTABILIZATION OWING TO IMPACTS FROM EARLIER CONVECTION...THE
POTENTIAL INCREASE IN INSTABILITY AND EXPECTED MAGNITUDE OF
ASCENT/DEEP SHEAR WARRANT THE MAINTENANCE OF THE SLIGHT RISK.

..MEAD/COHEN.. 10/13/2012

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