SWODY1
SPC AC 201629
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1129 AM CDT FRI APR 20 2007
VALID 201630Z - 211200Z
..THERE IS A SLGT RISK OF SVR TSTMS FROM SD SWD INTO WRN KS...
..SYNOPSIS...
UPR LOW EXPECTED TO CONTINUE SE ALONG THE CNTRL CA CST TODAY BEFORE
TURNING MORE E/SE ACROSS SRN CA/SW AZ EARLY SATURDAY. DOWNSTREAM
SYSTEM SHOULD WEAKEN AS IT LIFTS FARTHER N INTO SASKATCHEWAN/
MANITOBA...WHILE TRAILING COLD FRONT BECOMES STATIONARY NE/SW ACROSS
THE DAKOTAS. LEE TROUGH WILL STRENGTHEN OVER THE HI PLNS
..ESPECIALLY TONIGHT AND EARLY SATURDAY.
BOUNDARY LAYER MOISTURE...IN THE FORM OF A MODIFYING RETURNING POLAR
AIR...WILL SLOWLY INCREASE OVER THE HI PLNS...WITH DEWPOINTS ALONG
LEE TROUGH POSSIBLY REACHING THE LOW TO MID 50S NWD INTO WRN NEB BY
AFTERNOON. HEIGHT FALLS WITH CA SYSTEM WILL REMAIN W OF THE PLNS
UNTIL AFTER 06Z SATURDAY. THUS...WHILE LEE TROUGH/DRY LINE MAY MIX
A LITTLE E BY THIS AFTERNOON...FEATURE SHOULD REDEVELOP W INTO ERN
CO TONIGHT.
..CNTRL/SRN HI PLNS...
VEERING WIND PROFILES...STEEP LOW TO MID LEVEL LAPSE RATES AND
SLOWLY INCREASING LOW LEVEL MOISTURE WILL SUPPORT A CONDITIONAL
THREAT FOR SUPERCELL DEVELOPMENT BY LATE AFTERNOON ALONG LEE
TROUGH/DRY LINE FROM WRN NEB/KS SWD INTO W CNTRL TX.
SATELLITE AND MODEL DATA INDICATE THAT MID LEVEL COOLING/HEIGHT
FALLS WILL BE ABSENT ACROSS MOST OF THIS REGION THROUGH EARLY
TONIGHT. IN W CNTRL TX...WV IMAGERY DOES SUGGEST PRESENCE OF A WEAK
HI LEVEL IMPULSE NOW ENTERING FAR W TX THAT SHOULD REACH THE TX
SOUTH PLNS BY LATE IN THE DAY. FOR THE MOST PART...HOWEVER ...ANY
DEEP CONVECTIVE DEVELOPMENT WILL BE TIED TO CONVERGENCE/ HEATING
ALONG LEE TROUGH/DRY LINE.
ANY STORMS THAT DO FORM WILL HAVE THE POTENTIAL FOR LARGE HAIL
BEFORE BOUNDARY LAYER BEGINS TO DECOUPLE. RELATIVELY SPARSE
MOISTURE SUPPLY AND CONVERGENCE TOGETHER SHOULD LIMIT OVERALL STORM
COVERAGE.
..DAKOTAS...
A MORE WIDESPREAD AREA OF STORMS EXPECTED TO FORM LATER THIS
AFTERNOON THROUGH EARLY SATURDAY INVOF STALLING FRONT FROM NRN
NEB/SD NEWD INTO ND/NW MN AS SSWLY LLJ STRENGTHENS TO AOA 40-50 KTS.
MOST OF THIS ACTIVITY SHOULD BE ELEVATED. BUT WITH MUCAPE AOA 1000
J/KG AND CLOUD LAYER SHEAR AOA 40 KTS...STORMS COULD YIELD SEVERE
HAIL AND POSSIBLY HIGH WIND...ESPECIALLY IN NEB/SRN SD LATE TODAY
THROUGH EARLY TONIGHT.
..SRN CA...
AXIS OF ENHANCED DEEP SHEAR ASSOCIATED WITH UPR LOW DROPPING SE
ALONG THE CNTRL CA CST WILL REMAIN OFFSHORE TODAY...AND ENTER NW
MEXICO THIS EVENING. AT THE SAME TIME...THE AREAS MOST FAVORABLE
FOR DEEP ASCENT IN EXIT REGION OF ASSOCIATED JET STREAK ARE EXPECTED
TO REMAIN CLOUDY TODAY. THUS...PROSPECTS FOR STRONG STORMS IN THE
LAX OR SAN AREAS APPEARS LOW.
.CORFIDI/DARROW.. 04/20/2007
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