DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 241956
SWODY1
SPC AC 241953

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0253 PM CDT WED OCT 24 2012

VALID 242000Z - 251200Z

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

NO CHANGES HAVE BEEN MADE TO THE CONVECTIVE OUTLOOK GRAPHICS.

EARLY AFTERNOON SURFACE ANALYSIS SHOWED AN AREA OF LOW PRESSURE HAD
MOVED INTO CENTRAL IA ALONG THE STATIONARY FRONT...WITH THIS
BOUNDARY EXTENDING NNEWD THROUGH SERN MN TO NWRN WI. THE TRAILING
PORTION OF THIS FRONT HAD MOVED VERY LITTLE...IF AT ALL...SINCE THIS
MORNING AND EXTENDED THROUGH SWRN IA TO SWRN KS TO THE BORDER AREA
OF THE OK/TX PANHANDLES. SATELLITE IMAGERY INDICATED SHALLOW
CONVECTIVE ROLLS ORIENTED PARALLEL TO THE SURFACE FRONT...AND
LOCATED NEAR AND JUST E THROUGH SW OF THE SURFACE LOW WHERE
OBJECTIVE ANALYSES SHOWED GREATER CONVERGENCE. TRENDS IN WIND
PROFILERS/WSR-88D VADS ACROSS KS AND WATER VAPOR IMAGERY SUGGEST A
LEAD MIDLEVEL IMPULSE IS TRACKING NEWD ACROSS THIS REGION. ASCENT
WITH THIS FEATURE MAY BE AIDING IN THE CONVECTIVE DEVELOPMENT
EVIDENT ACROSS IA...BUT MODIFIED 12Z OMA SOUNDING WITH AN AVERAGE OF
WARM SECTOR SURFACE TEMPERATURES/DEW POINTS /75 F AND 66 F
RESPECTIVELY/ KEEP THE ENVIRONMENT CAPPED.

14-16Z HRRR RUNS SUGGEST CONVECTION WILL DEVELOP NEAR THE TWIN
CITIES METRO AROUND 21Z AND SPREAD NEWD...BUT GIVEN THE EXTENSIVE
CLOUD COVER AND POSITION OF THE FRONT...ANY TSTMS SHOULD TEND TO BE
ELEVATED. WEAK INSTABILITY COULD SUPPORT SMALL HAIL. OTHERWISE...
THE REST OF THE FORECAST THREATS REMAIN ON TRACK AND THERE IS NO
CURRENT INDICATION FOR DEEP CONVECTION IN THE SHORT TERM /THROUGH
THE LATE AFTERNOON/.

..PETERS.. 10/24/2012

.PREV DISCUSSION... /ISSUED 1114 AM CDT WED OCT 24 2012/

...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.

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