SWODY1
SPC AC 300600
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT FRI MAY 30 2008
VALID 301200Z - 311200Z
...THERE IS A MDT RISK OF SVR TSTMS OVER A SMALL PART OF THE
MIDWEST...
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CNTRL/SRN PLAINS NEWD
INTO THE CNTRL GRTLKS REGION...
...SYNOPSIS...
A MORE ZONAL UPR FLOW REGIME WILL EXIST ON FRIDAY WITH A FAST BAND
OF WLYS PROMINENT ACROSS THE CNTRL/NRN PARTS OF THE COUNTRY. THIS
JET WILL CARRY A LEAD IMPULSE...NOW MOVING ACROSS THE MO
VLY...QUICKLY ENE INTO THE GRTLKS REGION/ONTARIO BY FRIDAY EVENING.
ANOTHER DISTURBANCE...CURRENTLY OVER ND...WILL EVENTUALLY ACT TO
BUCKLE THE NRN STREAM...CARVING OUT A POSITIVE-TILT TROUGH THAT WILL
MOVE TOWARD THE GRTLKS/MIDWEST BY FRIDAY NIGHT.
IN THE LWR-LVLS...PRIMARY SFC LOW WILL DEVELOP NEWD FROM THE CORN
BELT INTO THE UPR GRTLKS REGION BY FRIDAY EVENING AS THE LEAD
IMPULSE EXITS INTO CANADA. THE TRAILING COLD FRONT WILL BECOME
SOMEWHAT DISJOINTED OWING TO OUTFLOW FROM NOCTURNAL MCS/S...WITH THE
EFFECTIVE FRONT LIKELY SITUATED FROM NRN/CNTRL IL/IND SWWD INTO
CNTRL MO/KS. TO THE NW...SEVERAL BOUNDARIES/TROUGHS WILL
EXIST...WITH STRONGEST ASSOCD WITH THE NRN STREAM IMPULSE...ACROSS
THE ERN DAKS/WRN MN INTO IA.
...GRTLKS REGION SWWD INTO THE CNTRL PLAINS...
A COMPLEX SVR SCENARIO WILL UNFOLD BY THE BEGINNING OF THE PERIOD
THAT WILL LIKELY RESULT IN LAST MINUTE ADJUSTMENTS TO THE ONGOING
MODERATE RISK. TSTMS GROWING UPSCALE INTO BOTH ELEVATED CLUSTERS
OVER THE GRTLKS AND SFC-BASED...SMALL SCALE LEWPS/BOWS OVER THE MO
VLY/CORN BELT EARLY FRIDAY MORNING WILL CONTINUE ENE. SOME OF THIS
ACTIVITY MAY ALREADY BE PRODUCING LOCALLY HIGH WINDS/HAIL OVER THE
CNTRL LAKES REGION SWWD INTO NRN MO AT 12Z FRIDAY. DECAYING
CONVECTION/CLOUDS DOWNSTREAM FROM THIS ACTIVITY WILL TEND TO LIMIT
SFC HEATING/DESTAB LATER IN THE DAY.
CURRENT THINKING IS THAT THE FOOTPRINT OF MORNING CONVECTION WILL
BECOME SITUATED FROM NRN/CNTRL MO NEWD ACROSS CNTRL IL/NRN IND LATE
FRIDAY MORNING. AIR MASS ALONG/S OF THIS BOUNDARY WILL BECOME
MODESTLY UNSTABLE AS UPR 60S DEW POINTS RESIDE BENEATH MODEST
MID-LVL LAPSE RATES. BY AFTN...MLCAPES SHOULD RANGE FROM 2000-2500
J/KG...SLIGHTLY HIGHER WITH WWD EXTENT ALONG THE BOUNDARY. AS
LARGER SCALE ASCENT BRUSHES THIS WARM SECTOR...TSTMS SHOULD EASILY
DEVELOP...FIRST IN THE MIDWEST...THEN BACKBUILDING SWWD DURING THE
AFTN AS FAR W AS KS/NRN OK.
THE LOW-LEVEL FLOW IS EXPECTED TO BE VEER WITH TIME THROUGHOUT THE
DAY ALONG THE BOUNDARY. BUT...SUFFICIENT SPEED SHEAR WILL EXIST
WITH RESULTANT LARGE HODOGRAPHS. THIS WILL SUPPORT SUPERCELLS WITH
ROUGHLY 45-50 KTS OF BULK SHEAR EXPECTED. MOST SUBSTANTIAL
CROSS-OVER WILL PROBABLY OCCUR WITHIN THE MDT RISK AREA WHERE A FEW
TORNADOES WILL BE POSSIBLE EARLY IN SUPERCELL LIFE-CYCLES.
OTHERWISE...LARGE HAIL AND DMGG WINDS WILL BE LIKELY.
ONE OR MORE TSTM CLUSTERS /BOW ECHOES/ MAY EVOLVE DURING THE
EVENING...REACHING THE LWR GRTLKS AND OH VLY REGIONS BY 12Z
SATURDAY. MOST SUBSTANTIAL STORMS MAY FAVOR THE STRONGER ZONE OF
LOW-LVL THETA-E ADVECTION IN THE OH VLY. DMGG WINDS WILL BE A
THREAT WELL INTO THE NIGHT. FARTHER W...ACTIVITY WILL EVENTUALLY
FADE WITH LOSS OF HEATING W OF THE MS RVR VLY.
...NRN PLAINS...
WELL TO THE NW OF THE SVR HIGHLIGHTS IN THE MIDWEST/PLAINS...A
SEPARATE REGION OF AT LEAST ISOLD...DIURNALLY BASED SVR STORMS MAY
EVOLVE BENEATH COLD TEMPERATURES ALOFT OVER A LARGER REGION FROM ERN
MT TO MN. MID-MINUS TEENS H5 COLD POOL ALOFT ATOP RESIDUAL 50S SFC
DEW POINTS AND NUMEROUS LOW-LEVEL BOUNDARIES WILL CONTRIBUTE TO STG
STORMS. WEAK BULK SHEAR WILL YIELD PULSE TYPE-HAIL STORMS FOR THE
MOST PART. PARTS OF THE ERN DAKS AND MN MAY EVENTUALLY NEED AN
UPGRADE TO A CATEGORICAL SLGT RISK ONCE THE THERMODYNAMIC
ENVIRONMENT BECOMES BETTER DEFINED.
..RACY/HURLBUT.. 05/30/2008
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