SWODY1
SPC AC 291958
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0258 PM CDT SUN APR 29 2007
VALID 292000Z - 301200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF SW...SCNTRL
TX...
..TRANSPECOS/EDWARDS PLATEAU/SRN AND CNTRL TX AND SRN NM...
MID-LEVEL DRY SLOT WRAPPING ALONG ERN PERIPHERY OF THE NRN MEXICAN
UPR LOW ALLOWED STRONG INSOLATION TO RAPIDLY WARM THE BOUNDARY LAYER
ACROSS THE BIG BEND REGION NWD INTO THE TRANSPECOS. MOIST SELY
UPSLOPE FLOW INTO THE HIGHER TERRAIN AND STRONG HEATING BENEATH
STEEP LAPSE RATES ALOFT HAVE BEEN FAVORABLE FOR DEEP MOIST
CONVECTION. THESE STORMS HAVE MOVED NWD INTO THE PERMIAN BASIN
REGION AT MID-AFTN. MOST OF THE TSTMS HAVE WEAKENED...BUT
MAINTENANCE OF STRONG STORMS HAS BEEN FAVORING PARTS OF THE BIG
COUNTRY WHERE MORE SFC HEATING HAS OCCURRED ON NW PERIPHERY OF
HIGHER PWAT VALUES. THESE STORMS MAY PRODUCE ISOLD DAMAGING WINDS
INTO PARTS OF WRN N TX LATE THIS AFTN.
NEXT VORTICITY LOBE WAS ROTATING NEWD TOWARD THE BIG BEND AND FAR W
TX WHERE AIR MASS HAS WARMED IN WAKE OF THE EARLIER STORMS. AS A
RESULT...TSTMS WILL LIKELY DEVELOP OVER/MOVE INTO SWRN TX LATER THIS
AFTN AND AT POINTS FARTHER N OVERNIGHT.
STRONGEST BELT OF FLOW WRAPPING AROUND THE UPR LOW WAS ARCING FROM
NRN COAHUILA/CHIHUAHUA INTO THE BIG BEND REGION...WITH VERTICAL
SHEAR SUFFICIENT FOR SUPERCELL STRUCTURES GIVEN ESELY SFC FLOW.
LARGE HAIL WILL BE THE PRIMARY SVR THREAT...BUT...A TORNADO OR TWO
CANNOT BE RULED OUT AS THE STORMS MATURE OVER THE STOCKTON PLATEAU.
FARTHER NW...FLOW ALOFT WAS WEAKER CLOSER TO THE CORE OF THE UPR
LOW. BUT...LAPSE RATES WERE QUITE STEEP AND INJECTION OF LOW-LEVEL
MOISTURE FROM THE EAST AND SOME HEATING WILL CONTRIBUTE TO
SUFFICIENT BUOYANCY FOR STRONG TO ISOLD SVR STORMS WITH LARGE HAIL
AND DAMAGING WINDS.
ACROSS SCNTRL/CNTRL TX...WDLY SCT TSTMS WILL LIKELY FORM ALONG THE
ESCARPMENT/COASTAL PLAIN/SEA BREEZE. HERE...MID-LEVEL TEMPERATURES
HAVE WARMED A DEGREE OR TWO CELSIUS OVER YESTERDAY.
BUT...THERMODYNAMIC SET-UP MAY PROVE FAVORABLE FOR ISOLD STRONG
STORMS WITH HAIL OR DAMAGING WINDS.
..UPR MS RVR VLY...
PRE-FRONTAL TROUGH HAS DEVELOPED FROM NERN WI SWWD TO NEAR KLSE THEN
INTO NRN NEB WITH PRIMARY COLD FRONT FROM LKSUP TO SERN SD. VSBL
SATL SHOWS SFC-BASED CU BEGINNING TO FORM AMONGST THE ACCAS FIELD.
SFC TEMPERATURES HAVE SOARED INTO THE UPPER 80S...BUT DEW POINTS
REMAINED IN THE UPPER 40S TO MID 50S. THIS HAS RESULTED IN A DEEP
AND RELATIVELY DRY BOUNDARY LAYER CHARACTERIZED BY MLCAPES TO AOB
500 J/KG. AS CONVERGENCE INCREASES VCNTY THE SFC TROUGH...LATE
AFTN/EVE HIGH-BASED TSTMS MAY DEVELOP OVER THE TRI-STATE REGION OF
SRN MN/NRN IA/SWRN WI...WHERE WIND PROFILES WILL BE FAVORABLE FOR
SUPERCELLS. CONFIDENCE REMAINS LOW FOR STORM
INITIATION/COVERAGE...BUT GIVEN A STORM...LARGE HAIL WILL BE THE
PRIMARY SVR THREAT.
..MT...
A MID-LEVEL SHORTWAVE TROUGH OVER PAC NW WILL MOVE ACROSS MT AND SRN
ALBERTA/SASKATCHEWAN BY TONIGHT. ASCENT WITH THIS WAVE WILL BE
FOCUSED ALONG THE ACCOMPANYING COLD FRONT THAT WILL MOVE ACROSS MT
LATE THIS AFTERNOON INTO TONIGHT. LOW-LEVEL MOISTURE IS QUITE
LIMITED IN ADVANCE OF THIS SYSTEM...AND ANY INSTABILITY THIS
AFTERNOON/EVENING WILL BE DRIVEN PRIMARILY BY WARM SURFACE
TEMPERATURES AND RESULTANT STEEP LAPSE RATES/DEEP MIXED
LAYERS. GIVEN THE FOCUSED ASCENT...STEEP LAPSE RATES...AND STRONG
VERTICAL SHEAR...A FEW HIGH-BASED STORMS COULD PRODUCE ISOLATED
DAMAGING WINDS LATE THIS AFTERNOON INTO EARLY TONIGHT.
.RACY.. 04/29/2007
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