SWODY1
SPC AC 211631
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1131 AM CDT SAT APR 21 2007
VALID 211630Z - 221200Z
..THERE IS A MDT RISK OF SVR TSTMS OVER MUCH OF THE CNTRL AND SRN
HI PLNS...
..THERE IS A SLGT RISK OF SVR TSTMS OVER MUCH OF THE REMAINDER OF
THE CNTRL AND SRN PLNS TO THE UPR MS VLY...
..SYNOPSIS...
POTENT UPR LOW/TROUGH OVER ERN AZ IS EJECTING STEADILY EWD ATTM.
THE SYSTEM SHOULD TURN ENE LATER TODAY...REACH NE NM THIS EVENING
..AND THEN ACCELERATE TOWARD THE OMAHA AREA BY 12Z SUNDAY.
90+ KT SPEED MAX ROUNDING BASE OF TROUGH SHOULD REACH W TX THIS
EVENING BEFORE WEAKENING SOMEWHAT AS IT REDEVELOPS NE ACROSS NW
OK/KS EARLY SUNDAY.
AT THE SFC...LEE CYCLONE EXPECTED TO REMAIN STATIONARY AS IT DEEPENS
OVER ERN CO TODAY/EARLY TONIGHT...WITH THE LOW MOVING TO CNTRL NEB
BY 12Z SUNDAY. IN THE MEANTIME...A SERIES OF WEAK WAVES SHOULD
PERSIST ALONG STATIONARY FRONT EXTENDING NE FROM THE LOW INTO MN.
..CNTRL/SRN HI PLNS...
SFC HEATING AND FAVORABLY-TIMED ARRIVAL OF ENHANCED ASCENT IN EXIT
REGION OF APPROACHING SPEED MAX SHOULD SUPPORT RAPID STORM
DEVELOPMENT INVOF SFC LOW/FRONT/LEE TROUGH OVER SW NEB/NE CO SWD
INTO THE OK/TX PANHANDLES BY MID TO LATE AFTERNOON. WITH LOW
THROUGH MID LAPSE RATES IN EXCESS OF 8C/KM...MLCAPE TO 2000 J/KG AND
50-60KT OF DEEP SSWLY SHEAR...THE ONLY LIMITING FACTOR PRECLUDING A
HIGHER RISK OF SVR WX IS MODEST LOW LEVEL MOISTURE.
LCLS WILL BE FAIRLY HIGH ALONG LEE TROUGH...ALTHOUGH PERSISTENT
CLOUDS MAY KEEP BOUNDARY FROM MIXING AS DEEPLY AS IT OTHERWISE MIGHT
OVER THE ERN PANHANDLES REGION. AT ANY RATE...GIVEN INTENSITY OF
WIND FIELD...AND LIKELIHOOD FOR AT LEAST SOME WINDOW OF OPPORTUNITY
FOR DISCRETE STORMS /ESPECIALLY IN NEB AND POSSIBLY OVER W
TX/...POTENTIAL WILL EXIST FOR A FEW STRONG TORNADOES PRIOR TO
LIKELY TRANSITION TO BROKEN LINE SEGMENTS BY LATE EVENING.
CONTINUED E/NE MOTION OF UPR SYSTEM AND NOCTURNAL DECOUPLING OF LLJ
COULD MAINTAIN/EXTEND A THREAT FOR ISOLATED TORNADOES EWD INTO
ADDITIONAL PARTS OF W TX/WRN OK/WRN KS AND CNTRL NEB AFTER DARK.
WITH TIME...HOWEVER...INITIALLY DISCRETE ACTIVITY SHOULD EVOLVE INTO
ONE OR MORE BROKEN SQUALL LINES. EMBEDDED SUPERCELLS IN THE LINES
WILL CARRY SVR THREAT FARTHER E INTO THE PLAINS LATER TONIGHT/EARLY
SUNDAY...WITH THE MAIN THREATS BEING HAIL/DAMAGING WIND.
..NRN PLNS...
SCTD SLIGHTLY ELEVATED TSTMS EXPECTED TO PERSIST/REDEVELOP IN
VICINITY OF STALLED FRONT FROM NRN SD INTO SE ND/MN. SFC-BASED
STORMS SHOULD ALSO FORM LATER THIS AFTERNOON ALONG AND S OF FRONT
FROM NW NEB INTO SRN/ERN SD. AMPLE /40-50 KT/ CLOUD LAYER SHEAR
WILL BE PRESENT FOR SUPERCELLS. MID LEVEL LAPSE RATES/TEMPERATURES
STILL APPEAR FAVORABLE FOR LARGE HAIL DESPITE LARGELY MERIDIONAL
NATURE OF UPR FLOW. WITH MLCAPES LOCALLY INCREASING TO AROUND 2000
J/KG AND RELATIVELY WEAK LINEAR COMPONENT OF FORCING...TORNADOES
WILL ALSO BE POSSIBLE. THIS THREAT MAY BE GREATEST AS BOUNDARY
LAYER DECOUPLES/LLJ STRENGTHENS INTO MID EVENING.
.CORFIDI/CROSBIE.. 04/21/2007
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