SPC AC 112000
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0300 PM CDT FRI JUL 11 2008
VALID 112000Z - 121200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE UPPER
MIDWEST INTO THE CENTRAL PLAINS...
...UPPER MIDWEST INTO CENTRAL PLAINS...
WITH THE STRONG UPPER TROUGH CONTINUING TO SHIFT EASTWARD OVER THE
NORTHERN HIGH PLAINS PER WATER VAPOR IMAGERY...MID AFTERNOON SURFACE
ANALYSIS REFLECTS A CONTINUALLY DEEPENING 998 MB SURFACE LOW ACROSS
THE FAR EASTERN DAKOTAS...WITH THE ASSOCIATED COLD FRONT EXTENDING
SOUTH-SOUTHWESTWARD INTO EAST CENTRAL SD AND NORTHERN/WESTERN NEB.
EASTWARD FROM THE SURFACE LOW...A ROUGHLY NORTHWEST-SOUTHEAST
ORIENTED WARM FRONT CONTINUES TO LIFT NORTHWARD ACROSS
NORTHWEST/CENTRAL MN AND NORTHWEST WI. A VERY WARM BOUNDARY LAYER IS
IN PLACE WITHIN THE WARM SECTOR...WITH SURFACE DEWPOINTS IN THE
UPPER 60S/LOWER 70S F CONTRIBUTING TO STRONG INSTABILITY WITH
3000-4500 J/KG MLCAPE ACROSS THE FAR EASTERN DAKOTAS AND MUCH OF MN
PER RUC-BASED OBJECTIVE ANALYSIS.
A STRONG CAP IN PLACE PER MORNING 12Z RAOBS WILL LIKELY BE OVERCOME
DURING THE NEXT SEVERAL HOURS IN VICINITY OF THE SYNOPTIC COLD FRONT
/AND A SUBTLE PREFRONTAL TROUGH/ AS LARGE SCALE FORCING FOR ASCENT
OVERSPREADS THE REGION. AS APPEARS TO ALREADY BE OCCURRING...INITIAL
DEEP CONVECTIVE DEVELOPMENT APPEARS LIKELY INITIALLY ACROSS THE FAR
EASTERN DAKOTAS INTO NORTHERN/CENTRAL MN. THE COMBINATION OF VERY
FAVORABLE THERMODYNAMIC PARAMETERS AND EFFECTIVE SHEAR OF 40-50
KNOTS SUGGEST SUPERCELL STRUCTURES ARE LIKELY...CAPABLE OF VERY
LARGE HAIL AND DAMAGING WINDS. A RISK FOR TORNADOES APPEARS TO BE
RELATIVELY MAXIMIZED NEAR THE SURFACE WARM FRONT ACROSS
NORTHERN/CENTRAL MN /AND PERHAPS NORTHWEST WI/...WHERE BACKED
SOUTHEASTERLY LOW LEVEL WINDS AND LOW LCL VALUES ARE IN PLACE.
ACTIVITY WILL LIKELY SPREAD EASTWARD THROUGH THE EVENING...AFFECTING
MUCH OF MN/WI THROUGH THE NIGHT...WITH POTENTIAL FOR UPSCALE
DEVELOPMENT INTO ONE OR MORE SEVERE MCS/S LATER THIS EVENING.
SUPERCELLS AND BOW/LEWP STRUCTURES ARE EXPECTED TO MAINTAIN A RISK
OF DAMAGING WINDS AND HAIL ACROSS THE REGION WELL AFTER DARK.
FARTHER SOUTH...TSTMS ARE FORECAST TO DEVELOP SOUTHWARD ALONG THE
COLD FRONT INTO PARTS OF IA/NEB/KS LATER THIS AFTERNOON AND EARLY
EVENING. VERTICAL SHEAR WILL BE SOMEWHAT WEAKER ALONG THIS PORTION
OF THE COLD FRONT...BUT STEEP LOW-MID LEVEL LAPSE RATES AND DRY AIR
ALOFT WILL PROMOTE DOWNDRAFT PRODUCTION WITH A THREAT OF DAMAGING
WINDS IN STRONGER CELLS.
...AZ/CA...
A VERY MOIST AIRMASS REMAINS IN PLACE OVER PARTS OF AZ/CA...WITH
MORNING PSR/TUS SOUNDINGS AND GPS DATA SHOWING OVER 1.50 INCH PW
VALUES. A COMBINATION OF EXTENSIVE CLOUDINESS AND THE EFFECTS OF
YESTERDAYS STORMS WILL LIKELY SUPPRESS HEATING TODAY AND LIMIT
DESTABILIZATION. THIS IS EXPECTED TO LESSEN THE OVERALL RISK OF
SEVERE STORMS TODAY. NEVERTHELESS...LOCALLY DAMAGING THUNDERSTORM
WINDS WILL BE POSSIBLE IN THOSE AREAS WHERE STRONG HEATING OCCURS.
..GUYER/KIS.. 07/11/2008
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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