SWODY1
SPC AC 071644
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1144 AM CDT THU JUN 07 2007
VALID 071630Z - 081200Z
..THERE IS A HIGH RISK OF SVR TSTMS THIS AFTERNOON/EVENING FROM WRN
UPPER MI SSWWD ACROSS WI INTO EXTREME NW IL AND ERN IA...
..THERE IS A MDT RISK OF SVR TSTMS SURROUNDING THE HIGH RISK....FOR
THE MIDDLE AND UPPER MS VALLEY SWWD TO CENTRAL OK...
..THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK...FROM
THE GREAT LAKES TO THE RED RIVER VALLEY OF TX/OK...
..SIGNIFICANT SEVERE THUNDERSTORM/TORNADO OUTBREAK EXPECTED THIS
AFTERNOON/EVENING ACROSS PARTS OF THE UPPER-MIDDLE MS VALLEY INTO
OK...
..UPPER MS VALLEY THIS AFTERNOON/EVENING...
AN INTENSE LATE SEASON CYCLONE WILL MOVE NEWD FROM WRN MN INTO
ONTARIO IN CONJUNCTION WITH THE PRIMARY MID LEVEL SHORTWAVE TROUGH
AND AN ASSOCIATED 80-110 KT MID-UPPER JET. TRAILING THE SURFACE
LOW...A REMNANT DRYLINE/PACIFIC COLD FRONT WILL MOVE EWD ACROSS
MN/IA TODAY...AND INTO WI THIS EVENING. THIS BOUNDARY WILL CONTINUE
SWWD ACROSS NRN MO/SE KS/CENTRAL OK BY LATE THIS EVENING.
RECENT SURFACE OBSERVATIONS SHOW PRONOUNCED DRYING ACROSS SW MN AND
WRN IA...WITH VISIBLE IMAGERY SUGGESTING THAT THE PRIMARY CONVECTIVE
FOCUS THIS AFTERNOON WILL BE THE BROKEN BAND OF ENHANCED CUMULUS NOW
PASSING JUST E OF MSP AND DSM. BOUNDARY LAYER MOISTURE IS
INCREASING E OF THIS BOUNDARY...AND DEWPOINTS SHOULD REACH THE UPPER
60S INTO WI THIS AFTERNOON. THIS MOISTURE...COMBINED WITH AFTERNOON
TEMPERATURES IN THE LOWER 80S...WILL SUPPORT MODERATE INSTABILITY
/MLCAPE VALUES NEAR 1500 J/KG/ FROM ERN IA/NW IL INTO WI THIS
AFTERNOON/EVENING. THE PRONOUNCED CAP SHOWN IN THE GRB/DVN/ILX
SOUNDINGS WILL WEAKEN FROM THE W AS MID LEVEL TEMPERATURES
COOL...AND FROM BELOW IN CONJUNCTION WITH SURFACE HEATING/MOISTENING
AND LOW-LEVEL ASCENT ON THE BOUNDARY. SCATTERED THUNDERSTORMS WILL
LIKELY DEVELOP ALONG THE BOUNDARY BY MID AFTERNOON FROM WRN/CENTRAL
WI INTO ERN IA...AND STORMS WILL SPREAD RAPIDLY NEWD DURING THE
AFTERNOON/EVENING.
VERTICAL SHEAR IS FORECAST TO BE VERY STRONG IN THE WARM SECTOR THIS
AFTERNOON AS A RESULT OF 70-80 KT SWLY MID LEVEL FLOW. FORECAST
HODOGRAPHS ARE RELATIVELY LONG AND STRAIGHT WITH MODEST LOW-LEVEL
SHEAR. THOUGH DEEP LAYER SHEAR IS SOMEWHAT LINE PARALLEL...ONLY
MODEST FORCING FOR ASCENT AND STRONG VERTICAL SHEAR/MODERATE
INSTABILITY SUGGEST THAT THE INITIAL STORMS WILL GRADUALLY EVOLVE
INTO A BROKEN BAND OF FAST MOVING SUPERCELLS THIS AFTERNOON/EVENING.
THE INCREASING LOW-LEVEL MOISTURE AND MODERATELY STRONG LOW-LEVEL
SHEAR SUGGEST THAT A FEW STRONG TORNADOES WILL BE POSSIBLE AS THE
STORMS MATURE BY THIS EVENING...LIKELY FROM SW INTO E CENTRAL WI.
IF CONVECTION EVOLVES INTO A MORE LINEAR MODE...THEN EMBEDDED BOWING
SEGMENTS COULD PRODUCE SUBSTANTIAL DAMAGING WINDS.
OTHERWISE...LARGE HAIL CAN ALSO BE EXPECTED WITH THE MORE INTENSE
STORMS.
..NE SD INTO NE MN TODAY...
THE DEEP SURFACE CYCLONE WILL DEVELOP NEWD FROM THE ND/SD/MN BORDER
AS OF 16Z TO NE MN BY LATE AFTERNOON. STRONG/SEVERE STORMS CAN BE
EXPECTED ALONG THE PATH OF THE PRIMARY MID LEVEL VORTICITY MAXIMUM
FROM NE SD INTO NW MN THIS AFTERNOON...WHERE LARGE HAIL AND DAMAGING
GUSTS WILL BE POSSIBLE. AN ISOLATED TORNADO OR TWO MAY ALSO OCCUR.
THE TORNADO THREAT WILL BE SOMEWHAT GREATER FARTHER TO THE E IN
ADVANCE OF THE SURFACE LOW ACROSS N CENTRAL AND NE MN /REMOVED FROM
THE STABILIZING INFLUENCE OF LAKE SUPERIOR/. A FEW SUPERCELLS COULD
DEVELOP WITHIN THIS ZONE DURING THE AFTERNOON AS THE LOW LEVELS
DESTABILIZE UP TO THE WARM FRONT. OTHERWISE...LARGE HAIL AND
DAMAGING WINDS WILL ALSO BE POSSIBLE WITH THIS CONVECTION.
..WRN MO/SE KS INTO OK LATE THIS AFTERNOON INTO TONIGHT...
A SECONDARY MID LEVEL SPEED MAX OVER NRN AZ WILL TRANSLATE EWD TODAY
THEN ENEWD OVER SRN KS BY EARLY TONIGHT. THE REMNANT DRYLINE WILL
LIKELY STALL THIS EVENING FROM SE KS INTO CENTRAL OK AFTER MIXING
PEAKS AND THIS SPEED MAX APPROACHES FROM THE W.
MEANWHILE...AFTERNOON SURFACE TEMPERATURES IN THE MID-UPPER 80S IN
THE MOIST SECTOR WITH BOUNDARY LAYER DEWPOINTS OF 70-73 F WILL
RESULT IN STRONG INSTABILITY /MLCAPE VALUES OF 3000-4000 J/KG/ E OF
THE DRYLINE. THE PRONOUNCED CAP NOTED IN THE 12Z SOUNDINGS AT
OUN/FWD/SGF WILL LIKELY WEAKEN AS THE COOLER AIR IN THE 850-600 MB
LAYER AT AMA/DDC PROGRESSES EWD BY THIS EVENING...WITH CONVECTIVE
INITIATION BECOMING MORE PROBABLE FROM ABOUT 22-01Z.
THE STRONG INSTABILITY AND 0-6 KM BULK SHEAR OF 40-50 KT WILL
SUPPORT SUPERCELLS INTO THIS EVENING...WITH ISOLATED VERY LARGE HAIL
AND A FEW TORNADOES POSSIBLE. OVERNIGHT...CONVECTION MAY TEND TO
EXPAND IN COVERAGE ALONG THE BOUNDARY...POSSIBLY GROWING UPSCALE
INTO AN MCS ACROSS CENTRAL/NE OK...WITH LARGE HAIL AND DAMAGING
WINDS THE MAIN THREATS.
.THOMPSON/BRIGHT.. 06/07/2007
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