DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 241616
SWODY1
SPC AC 241614

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1114 AM CDT WED OCT 24 2012

VALID 241630Z - 251200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE UPPER
GREAT LAKES INTO THE MID MO VALLEY...

...SYNOPSIS...

A SIGNIFICANT VORTICITY MAXIMUM AND ASSOCIATED 70-80 KT MIDLEVEL JET
STREAK OVER THE SIERRA NEVADA RANGE AS OF MID MORNING WILL TRANSLATE
EWD THROUGH THE CNTRL ROCKIES...EVENTUALLY REACHING THE MID MO
VALLEY BY 25/12Z. THE PROGRESSION OF THESE FEATURES WILL RESULT IN
THE AMPLIFICATION OF A SYNOPTIC-SCALE TROUGH WHICH WILL ENCOMPASS
THE WRN TWO-THIRDS OF THE NATION BY THE END OF THE FORECAST PERIOD.

AT THE SURFACE...LOW PRESSURE OVER NERN KS/SERN NEB AS OF 15Z...WILL
DEVELOP NEWD ALONG A STATIONARY FRONT THROUGH CNTRL IA THIS
AFTERNOON AND INTO W-CNTRL WI BY THIS EVENING. THE STATIONARY FRONT
--EXTENDING FROM WRN WI THROUGH CNTRL KS INTO THE OK/NRN TX PNHDLS
AS OF MID MORNING-- WILL BEGIN TO ADVANCE EWD/SEWD TONIGHT AS IT IS
OVERTAKEN BY A COLD FRONT CURRENTLY POSITIONED FROM THE RED RIVER
VALLEY /ND AND MN/ INTO NRN HIGH PLAINS.

...UPPER GREAT LAKES INTO MID MO VALLEY LATE THIS AFTERNOON INTO
TONIGHT...

12Z REGIONAL SOUNDINGS SHOWED THE PRESENCE OF A PRONOUNCED CAP AT
THE BASE OF AN EML WHICH IS EXPECTED TO INHIBIT SURFACE-BASED STORM
DEVELOPMENT THROUGH MUCH OF THE AFTERNOON. THE LOW-LEVEL MASS
RESPONSE TO THE APPROACHING VORTICITY MAXIMUM AND JET STREAK
MENTIONED IN THE SYNOPSIS...AND MANIFEST AS A BROADENING AND
STRENGTHENING LLJ...WILL ENHANCE THE NWD FLUX OF AN INCREASINGLY
MOIST BOUNDARY LAYER BENEATH THE CAP. WHEN COUPLED WITH THE STEEP
MIDLEVEL LAPSE RATES AND FILTERED SUNSHINE...EXPECT AFTERNOON MLCAPE
VALUES TO APPROACH 1000-2000 J/KG.

LATEST CONVECTION-ALLOWING AND MESOSCALE MODEL GUIDANCE CONTINUES TO
INDICATE AN INCREASINGLY LIKELIHOOD FOR STORM DEVELOPMENT IN THE
24/21Z-25/00Z TIME FRAME AS THE CAP IS ERODED BY INCREASING HEIGHT
FALLS/DYNAMIC COOLING FROM THE WEST. THERE IS SOME INDICATION THAT
INITIAL STORM DEVELOPMENT MAY BE ROOTED ABOVE THE FRONTAL SURFACE
OVER SRN/CNTRL MN. THE GREATEST POTENTIAL FOR SURFACE-BASED STORMS
WILL BE TOWARD 25/00Z ACROSS NERN IA/SERN MN/WRN WI ALONG THE
IMMEDIATE FRONTAL INTERFACE WHERE LOW-LEVEL CONVERGENCE IS ENHANCED
AHEAD OF THE SURFACE LOW. SHOULD THIS SCENARIO UNFOLD...THE
PRESENCE OF 40-45 KT DEEP-LAYER SHEAR AND EFFECTIVE SRH VALUES OF
200-300 M2/S2 INDICATE THE POTENTIAL FOR SUPERCELLS CAPABLE OF A FEW
TORNADOES WITHIN THE FIRST 1-2 HRS AFTER INITIATION.
OTHERWISE...EXPECT THE PRIMARY HAZARDS TO BE SEVERE HAIL AND LOCALLY
DAMAGING WIND GUSTS.

SUBSEQUENT STORM DEVELOPMENT IS ANTICIPATED THIS EVENING INTO
TONIGHT SWWD INTO THE MID MO VALLEY WHERE SOME POTENTIAL FOR HAIL
AND DAMAGING WIND GUSTS WILL EXIST.

..MEAD/DISPIGNA.. 10/24/2012

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