SWODY1
SPC AC 201222
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0722 AM CDT FRI APR 20 2007
VALID 201300Z - 211200Z
..THERE IS A SLGT RISK OF SVR TSTMS FROM CENTRAL SOUTH DAKOTA SWD
TO NWRN KS...
..SYNOPSIS...
NEXT IN A SERIES OF POTENT S/WV TROUGHS DIGGING SEWD JUST OFF CA
COAST WITH DOWNSTREAM TROUGH RIDING NNEWD INTO SRN CANADA OVER THE
RIDGE IN THE CENTRAL CONUS. LEE TROUGHING E OF CENTRAL ROCKIES
CURRENTLY WILL INTENSIFY THROUGH THE AFTERNOON WITH CURRENT WEAK LOW
CENTER SERN CO SHIFTING INTO NEB PANHANDLE BY THIS EVENING.
LOW LEVEL MOISTURE SPREADING NWD E OF SURFACE TROUGH WITH DEWPOINTS
RISING INTO THE MID 50S NWD INTO WRN NEB BY THIS AFTERNOON. SURFACE
TROUGH/DRY LINE FROM CENTRAL TX PANHANDLE NWD ALONG KS/CO BORDER
WILL MIX A LITTLE E BY THIS AFTERNOON... RETURNING POSSIBLY AS FAR W
AS EXTREME CO BY THIS EVENING AS UPPER SUPPORT REMAINS WELL TO THE W
THROUGH THE FORECAST PERIOD.
..HIGH PLAINS...
VEERING SHEAR PROFILES...STEEP LAPSE RATES AND INCREASING LOW LEVEL
MOISTURE/INSTABILITY PROVIDE FOR A CONDITIONAL THREAT OF SUPERCELL
DEVELOPMENT BY MID/LATE AFTERNOON VICINITY LEE TROUGH/DRY LINE.
THERE WILL BE A LACK OF MID LEVEL COOLING AND UPPER SUPPORT ACROSS
THE DRY LINE TODAY AS THE CA TROUGH NOT EXPECTED TO BE A FACTOR
UNTIL SAT. THUS SURFACE INITIATION WILL BE TIED TO CONVERGENCE
VICINITY DRY LINE AND SURFACE HEATING.
MODEL GUIDANCE DOES SUPPORT AT LEAST A FEW SURFACE BASED STORMS
VICINITY CO/KS BORDER WITH A LITTLE GREATER THREAT INTO WRN NEB.
ANY STORMS THAT CAN DEVELOP COULD QUICKLY DEVELOP INTO A RELATIVELY
HIGH BASED SUPERCELL. PRIMARY THREAT WILL BE VERY LARGE HAIL THRU
THE EVENING WHEN SURFACE BOUNDARY LAYER SHOULD BEGIN DECOUPLING.
AMOUNT OF PRECIPITABLE WATER OF LESS THAN 3/4 INCHES SHOULD LIMIT
THE OVERALL STORM COVERAGE.
MORE WIDESPREAD THUNDERSTORMS EXPECTED OVERNIGHT NWD THRU THE
DAKOTAS AS INCREASING WARM ADVECTION ON 40-50KT LOW LEVEL JET
PROVIDES FAVORABLE LIFT. THESE STORMS SHOULD BE ROOTED WELL ABOVE
THE SURFACE...BUT GIVEN THE STEEP MID LEVEL LAPSE RATES AND
SHEAR...ROTATING STORMS AND ASSOCIATED MARGINAL SEVERE THREAT
EXPECTED...PRIMARILY LARGE HAIL.
.HALES/GRAMS.. 04/20/2007
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