SWODY1
SPC AC 170048
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0748 PM CDT WED JUL 16 2008
VALID 170100Z - 171200Z
...THERE IS A SLGT RISK OF SVR TSTMS TONIGHT ACROSS PARTS OF THE N
CNTRL PLAINS INTO UPPER MS VALLEY AND GREAT LAKES REGION....
...LOWER MI INTO THE LOWER GREAT LAKES REGION...
UPPER SUPPORT FOR CONVECTIVE ACTIVITY IS WEAK TO NEGLIGIBLE ACROSS
THE REGION...WITH THE PRIMARY SHORT WAVE IMPULSE WITHIN THE BELT OF
STRONGER POLAR WESTERLIES SHIFTING EAST NORTHEAST OF THE CENTRAL
CANADIAN/U.S. BORDER THROUGH AREAS OF ONTARIO NEAR/NORTH OF LAKE
SUPERIOR. AND...THE LOSS OF HEATING IN THE BOUNDARY LAYER IS
UNDERWAY...WHICH WILL LEAD TO GRADUAL STABILIZING TRENDS AND SLOWLY
DIMINISHING CONVECTIVE POTENTIAL. HOWEVER...LINGERING INSTABILITY
BASED ABOVE THE BOUNDARY LAYER...ON THE ORDER OF 2000+ J/KG...IN THE
PRESENCE OF CONTINUING WEAK LOWER/MID TROPOSPHERIC WARM
ADVECTION...MAY BE SUFFICIENT TO MAINTAIN STORM DEVELOPMENT CAPABLE
OF PRODUCING GUSTY WINDS AND MARGINALLY SEVERE HAIL THROUGH THE
EVENING HOURS.
WHILE CONSIDERABLE WEAKENING OF THE STORM CLUSTER SPREADING
SOUTHEAST OF LAKE MICHIGAN INTO SOUTHWESTERN LOWER MICHIGAN HAS
OCCURRED...A NEW CLUSTER APPEARS TO BE SLOWLY CONSOLIDATING IN WEAK
TO MODERATE SHEAR NORTHWEST THROUGH NORTH OF DETROIT. THE LATTER
SYSTEM COULD EVENTUALLY ADVANCE ACROSS SOUTHERN ONTARIO AND TO THE
LEE OF LAKE ERIE AFTER 17/06Z...WITH AT LEAST LOW POTENTIAL FOR A
CONTINUING RISK FOR GUSTY WINDS/HAIL APPROACHING OR BRIEFLY
EXCEEDING SEVERE LIMITED.
...NORTH CENTRAL PLAINS...
UPPER SUPPORT FOR CONVECTIVE DEVELOPMENT/GROWTH TONIGHT IS
UNCERTAIN...WITH THE MOST SIGNIFICANT UPSTREAM SHORT WAVE IMPULSE
NOT PROGGED TO PROGRESS OUT OF THE NORTHERN INTERMOUNTAIN REGION...
AND ACROSS THE NORTHERN ROCKIES...UNTIL LATE TONIGHT. BUT...
NOCTURNAL STRENGTHENING OF THE PLAINS SOUTHERLY LOW-LEVEL JET...AND
THE PRESENCE OF LARGE CAPE WITHIN A STEEP LAPSE RATE ENVIRONMENT...
PROVIDES POTENTIAL FOR SIGNIFICANT NEW STORM DEVELOPMENT TONIGHT.
LOWER/MID TROPOSPHERIC WARM ADVECTION AND CONVERGENCE SEEM LIKELY TO
FOCUS THIS ACTIVITY NEAR SURFACE TROUGH AND FRONTAL ZONE
INTERSECTION ACROSS EASTERN SOUTH DAKOTA. IF THIS OCCURS...DEEP
LAYER SHEAR BENEATH 30-40 KT WESTERLY 500 MB FLOW WILL BE FAVORABLE
FOR ANOTHER ORGANIZED MESOSCALE CONVECTIVE SYSTEM WITH POTENTIAL FOR
DAMAGING WIND GUSTS AND HAIL...WHICH PROBABLY WILL SPREAD EASTWARD
INTO MINNESOTA AND SOUTHWARD THROUGH EASTERN SOUTH DAKOTA LATE
TONIGHT.
..KERR.. 07/17/2008
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