SWODY1
SPC AC 171237
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0737 AM CDT TUE APR 17 2007
VALID 171300Z - 181200Z
..THERE IS A SLGT RISK OF SVR TSTMS TODAY INTO EARLY TONIGHT ACROSS
NW INTO N CENTRAL AND NE TX...
..SYNOPSIS...
A CLOSED MID LEVEL LOW OVER SW NM THIS MORNING WILL MOVE EWD INTO N
TX BY THIS EVENING AND THE LOWER MS VALLEY EARLY WED...AS AN
UPSTREAM TROUGH MOVES FROM THE PAC NW TO THE NRN GREAT BASIN. AT
THE SURFACE...A WEAK CYCLONE WILL ACCOMPANY THE SRN STREAM MID LEVEL
LOW FROM W CENTRAL INTO CENTRAL/N TX TODAY...WHILE THE ENTIRE SYSTEM
WILL BEGIN TO EVOLVE INTO MORE OF AN OPEN WAVE AND LOSE AMPLITUDE
OVERNIGHT.
..NW AND N CENTRAL TX THIS AFTERNOON...
A CORE OF STEEP L0W-MID LEVEL LAPSE RATES WILL SPREAD EWD FROM NM
INTO WRN AND CENTRAL TX BY THIS AFTERNOON IN ASSOCIATION WITH THE
MID LEVEL COLD POOL. HOWEVER...THE STEEPEST LAPSE RATES WILL BE
LIMITED TO A RELATIVELY SMALL AREA S AND W OF THE COMMA SHAPED ARC
OF CLOUDS/RAIN THAT WILL DEVELOP NEWD INTO OK TODAY IN ASSOCIATION
WITH A LEAD SHORTWAVE TROUGH ROTATING NEWD FROM W TX TOWARD SW OK.
THE PRIMARY SEVERE STORM THREAT TODAY IS EXPECTED TO EVOLVE FROM
THUNDERSTORM DEVELOPMENT BY MIDDAY INVOF THE TRIPLE POINT...ON THE
NE EDGE OF THE STEEPEST LOW-LEVEL LAPSE RATES/STRONGER SURFACE
HEATING AND THE NW EDGE OF THE BOUNDARY LAYER DEWPOINTS IN THE 50S.
THE SEVERE THREAT WILL BE FOCUSED FROM ABOUT 18-00Z ACROSS NW AND N
TX...WHILE THE SEVERE STORM THREAT SHOULD DECREASE AFTER SUNSET AS A
RESULT OF DIMINISHING LAPSE RATES WITH EWD EXTENT.
FORECAST SOUNDINGS /SUPPORTED BY UPSTREAM OBSERVATIONS/ SHOW RATHER
LARGE LOW-MID LEVEL BUOYANCY AND LOW EQUILIBRIUM LEVEL HEIGHTS OF
ONLY 7-8 KM AGL ACROSS N TX THIS AFTERNOON...AND RATHER MODEST
VERTICAL SHEAR THROUGH THE CLOUD LAYER IN THE REGION OF STRONGER
INSTABILITY. THE NET RESULT SHOULD BE ONE OR TWO CLUSTERS OF
VIGOROUS BUT RELATIVELY LOW-TOPPED STORMS CAPABLE OF PRODUCING LARGE
HAIL AND GUSTY OUTFLOW WINDS. THERE IS SOME POTENTIAL FOR
SUPERCELLS ON THE ERN EDGE OF THE INSTABILITY AND THE CYCLONIC SIDE
OF THE MID-UPPER JET...BUT THE THREAT FOR CLASSIC SUPERCELL
TORNADOES APPEARS QUITE MARGINAL. A COUPLE OF NON-MESOCYCLONE
TORNADOES MAY OCCUR IN CONJUNCTION WITH STEEP LOW-LEVEL LAPSE RATES
AND ENHANCED VERTICAL VORTICITY INVOF THE TRIPLE POINT THIS
AFTERNOON.
.THOMPSON/GRAMS.. 04/17/2007
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