DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 221246
SWODY1
SPC AC 221244

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0744 AM CDT TUE MAY 22 2007

VALID 221300Z - 231200Z

..THERE IS A SLGT RISK OF SVR TSTMS FROM SE SD ACROSS CENTRAL NEB
TO WRN KS THIS AFTERNOON INTO TONIGHT...

..SYNOPSIS...
A MID LEVEL LOW OVER WRN WY WILL LIFT NEWD TOWARD WRN ND AS AN
EMBEDDED SPEED MAX ROTATES EWD/NEWD AROUND THE SERN PERIPHERY OF THE
LOW TO WRN NEB BY THIS EVENING...AND THE CENTRAL/ERN DAKOTAS
OVERNIGHT. IN ADVANCE OF THIS MID LEVEL WAVE...A SURFACE CYCLONE IN
CENTRAL SD WILL DEVELOP NNEWD ACROSS ERN ND TO SE MANITOBA BY THIS
EVENING...WHILE A TRAILING COLD FRONT MOVES EWD ACROSS THE DAKOTAS
AND SEWD ACROSS NEB/NW KS. A SEPARATE LEE CYCLONE IN ERN CO THIS
MORNING WILL DEVELOP SWD TOWARD NE NM/NW TX PANHANDLE BY TONIGHT AS
SWLY FLOW ALOFT INCREASES OVER THE CO FRONT RANGE. THE COLD FRONT
ACROSS THE DAKOTAS/NEB...BACK TO THE TRIPLE POINT IN NW KS...WILL BE
THE PRIMARY FOCUS FOR STRONG/SEVERE THUNDERSTORM DEVELOPMENT THIS
AFTERNOON INTO TONIGHT.

..CENTRAL NEB TO WRN KS THIS AFTERNOON INTO TONIGHT...
LOW-LEVEL MOISTURE /BOUNDARY LAYER DEWPOINTS NEAR 60 F/ IS SPREADING
NWD FROM OK/ERN TX PANHANDLE TO KS ON A 35-50 KT LLJ THIS
MORNING...IN THE WAKE OF CONVECTIVE CLUSTERS THAT DISSIPATED
OVERNIGHT. THE REMAINING DEBRIS CLOUDINESS FROM OVERNIGHT
CONVECTION WILL GRADUALLY DIMINISH TODAY ACROSS KS/NEB...WHICH WILL
ALLOW SURFACE TEMPERATURES TO WARM INTO THE 80S NEAR AND S/SW OF THE
TRIPLE POINT THIS AFTERNOON. MLCAPE VALUES SHOULD INCREASE TO
1500-2500 J/KG IN CONJUNCTION WITH THE LOW-LEVEL WARMING AND
MOISTENING BENEATH A PLUME OF STEEP MID LEVEL LAPSE RATES. THE
WEAKER CONVECTIVE INHIBITION AND STRONGER LOW-LEVEL ASCENT ARE
EXPECTED NE OF THE TRIPLE POINT FROM NW KS INTO CENTRAL NEB ALONG
THE COLD FRONT THIS AFTERNOON/EVENING.

WHILE THE LOW LEVELS DESTABILIZE DURING THE AFTERNOON...DEEP LAYER
VERTICAL SHEAR WILL INCREASE NEAR AND JUST NE OF THE TRIPLE
POINT...ON THE NOSE OF THE MID-UPPER JET EJECTING NEWD OVER THE
CENTRAL HIGH PLAINS. MEANWHILE...L0W-LEVEL SHEAR WILL INCREASE
AGAIN THIS EVENING IN ASSOCIATION WITH A STRENGTHENING LLJ ACROSS
KS/OK. THE NET RESULT WILL BE A FAVORABLE ENVIRONMENT FOR
SUPERCELLS WITH VERY LARGE HAIL AND A FEW TORNADOES FROM LATE
AFTERNOON INTO THE LATE EVENING. THE WINDOW OF OPPORTUNITY FOR
DISCRETE STORMS COULD BE LIMITED BY DEEP LAYER FLOW/SHEAR SOMEWHAT
PARALLEL TO THE COLD FRONT...AND PERSISTENT MOISTURE INFLUX INTO THE
FRONTAL ZONE WHICH WILL FAVOR UPSCALE GROWTH INTO A LINEAR MCS
TONIGHT ACROSS NRN KS/NEB.

..EXTREME SW KS TO THE ERN TX PANHANDLE THIS EVENING...
THE DRYLINE IS FORECAST TO REMAIN CAPPED THROUGH MOST OF THE PERIOD.
HOWEVER...AFTERNOON TEMPERATURES IN THE MID-UPPER 80S ALONG THE
DRYLINE MAY RESULT IN SUFFICIENT MIXING TO SUPPORT THE DEVELOPMENT
OF AN ISOLATED STORM OR TWO FOR A COUPLE OF HOURS THIS EVENING INVOF
THE ERN TX PANHANDLE. IF DEEP CONVECTION DOES FORM...INSTABILITY
AND VERTICAL SHEAR SHOULD BE SUFFICIENT FOR SUPERCELLS WITH LARGE
HAIL BEFORE THE BOUNDARY LAYER COOLS/STABILIZES LATE THIS EVENING.

..NE SD INTO ERN ND/NW MN TODAY...
PRIOR CONVECTION HAS EXHAUSTED MUCH OF THE INSTABILITY ACROSS
ND...WITH ONLY A NARROW CORRIDOR OF RICHER MOISTURE FROM NE SD INTO
SE ND AND NW MN. A WELL-DEFINED MCV IS MOVING TOWARD THIS AREA FROM
CENTRAL SD...AND CONVECTION WITH THIS FEATURE WILL LIKELY REMOVE
MUCH OF THE LINGERING INSTABILITY DURING THE FIRST HALF OF THE DAY.
THEREFORE...ANY SEVERE STORM THREAT THIS AREA SHOULD REMAIN
MARGINAL.

..E/SE TX AREA TODAY...
ONGOING CONVECTIVE CLUSTER OVER SE TX WILL MOVE EWD TOWARD SW LA
TODAY IN CONJUNCTION WITH A SERIES OF VORTICITY MAXIMA WITHIN THE
SUBTROPICAL JET. HOWEVER...THE STORMS WILL LIKELY MOVE E OF THE
PRIMARY MOISTURE/INSTABILITY AXIS RELATIVELY EARLY IN THE DAY...THUS
THE THREAT FOR SEVERE STORMS SHOULD QUICKLY DIMINISH THIS MORNING.

.THOMPSON/TAYLOR.. 05/22/2007

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