SPC AC 010051
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0751 PM CDT MON APR 30 2007
VALID 010100Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF SCNTRL AND SE
TX...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE UPPER
MIDWEST...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF ERN OK...
...SRN PLAINS...
LATEST WATER VAPOR IMAGERY SHOWS A WELL-DEFINED UPPER-LEVEL LOW
CENTERED OVER THE CAPROCK OF WEST TX. A DRY SLOT IS LOCATED ACROSS
FAR WEST TX AND SOUTHWEST TX EXTENDING EWD INTO THE TX HILL COUNTRY.
SUBSIDENT AIR IS LIKELY LOCATED IN THIS REGION AND THUNDERSTORM
DEVELOPMENT THIS EVENING DOES NOT APPEAR LIKELY ACROSS MOST OF
SOUTHWEST TX AND THE TX HILL COUNTRY. SCATTERED TO NUMEROUS
THUNDERSTORMS ARE ONGOING ALONG THE EDGE OF THE DRY SLOT WHERE
LARGE-SCALE ASCENT IS MORE FAVORABLE FROM NCNTRL TX EXTENDING SEWD
INTO SE TX AND SWWD ALONG THE TX GULF COASTAL PLAIN. OTHER STORMS
ARE BEGINNING TO DEVELOP ALONG THE RED RIVER AND THESE CELLS SHOULD
SPREAD NWD INTO OK THIS EVENING.
FORECAST SOUNDINGS ACROSS SOUTH TX THIS EVENING SHOW STRONG VERTICAL
SHEAR WITH 0-6 KM SHEAR VALUES IN THE 40 TO 55 KT RANGE. THIS SHOULD
BE FAVORABLE FOR SUPERCELLS CONSIDERING MLCAPE VALUES RANGE FROM
2000 TO 3500 J/KG ACROSS SOUTH TX. INSTABILITY SHOULD BE ENOUGH TO
KEEP THE SUPERCELL THREAT GOING FOR MOST OF THE REMAINDER OF THE
EVENING. SUPERCELLS SHOULD HAVE A THREAT FOR LARGE HAIL AND ISOLATED
WIND DAMAGE. A TORNADO OR TWO IS ALSO POSSIBLE WITH THE STRONGEST
SUPERCELLS DUE TO ABUNDANT LOW-LEVEL MOISTURE...LOW LCL HEIGHTS AND
FAVORABLE LOW-LEVEL SHEAR PROFILES. FURTHER NORTHWEST...AN
INSTABILITY AXIS EXISTS FROM THE DEL RIO TX AREA EXTENDING NWD TO
AROUND ABILENE TX. AN ISOLATED SUPERCELL THREAT SHOULD ALSO EXIST IN
NCNTRL TX FOR A FEW MORE HOURS ON THE NORTH END OF THE STRONGER
INSTABILITY.
OTHER STRONG TO SEVERE STORMS ARE DEVELOPING ACROSS ERN OK ALONG AN
AXIS OF INSTABILITY IN RESPONSE TO INCREASING LIFT ASSOCIATED WITH
THE UPPER-LEVEL LOW. ALTHOUGH SHEAR PROFILES ARE NOT THAT
STRONG...MID-LEVEL LAPSE RATES SHOULD BE STEEP ENOUGH FOR HAIL WITH
THE STRONGER CELL THIS EVENING.
...UPPER MIDWEST...
LATEST WATER VAPOR IMAGERY SHOWS A SHORTWAVE TROUGH OVER WI. A SFC
LOW EXISTS ACROSS FAR NW IA WITH A WARM FRONT EXTENDING ESEWD ACROSS
FAR SRN MN...ERN IA INTO NRN IL. SCATTERED THUNDERSTORMS HAVE
DEVELOPED ABOUT 100 MILES NORTH OF THE BOUNDARY AND ARE ELEVATED IN
NATURE. SFC BASED THUNDERSTORM DEVELOPMENT ALONG THE BOUNDARY
APPEARS UNLIKELY AND THE SEVERE THREAT SHOULD BE CONFINED TO THE
ELEVATED CONVECTION NORTH OF THE FRONT THIS EVENING. STEEP MID-LEVEL
LAPSE RATES AND STRONG VERTICAL SHEAR SHOWN ON FORECAST SOUNDINGS
WILL BE FAVORABLE FOR LARGE HAIL WITH THE STRONGER CELLS.
...CNTRL HIGH PLAINS...
SCATTERED THUNDERSTORMS HAVE DEVELOPED ON THE CHEYENNE RIDGE EARLY
THIS EVENING LIKELY IN RESPONSE TO SFC HEATING...TOPOGRAPHIC FORCING
IN THE WAKE OF A COLD FRONT PASSAGE. ACCORDING TO OBJECTIVE
ANALYSIS...AN AXIS OF INSTABILITY EXISTS FROM FAR SE WY EXTENDING
EWD ACROSS SCNTRL NEB. WEAK LARGE-SCALE ASCENT ASSOCIATED WITH A
SUBTLE SHORTWAVE TROUGH EVIDENT ON WATER VAPOR IMAGERY AND THE
INSTABILITY SHOULD SUSTAIN THE STORMS FOR A FEW MORE HOURS. VERY
STEEP LAPSE RATES AND INVERTED-V PROFILES SHOWN ON FORECAST
SOUNDINGS SUGGEST EITHER HAIL OR STRONG GUSTY WINDS WILL BE POSSIBLE
WITH THE STRONGER THUNDERSTORMS THIS EVENING.
..BROYLES.. 05/01/2007
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