SWODY1
SPC AC 230548
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1248 AM CDT SUN SEP 23 2007
VALID 231200Z - 241200Z
..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF THE NRN PLAINS
AND CNTRL HIGH PLAINS...
..NRN PLAINS AND CNTRL HIGH PLAINS...
AN UPPER-LEVEL LOW OVER NV EARLY TODAY WILL OPEN UP AS HEIGHTS FALL
ACROSS THE NRN AND CNTRL HIGH PLAINS. IN RESPONSE...A SFC LOW WILL
ORGANIZE OVER ERN MT WITH A WELL-DEFINED SFC TROUGH EXTENDING SSWWD
FROM NCNTRL ND INTO WRN NEB. A SURGE OF LOW-LEVEL MOISTURE INTO THE
NRN PLAINS SHOULD TAKE PLACE TODAY ASSOCIATED WITH A STRONG PLAINS
LOW-LEVEL JET. SFC DEWPOINTS SHOULD AT LEAST REACH 60 F IN PARTS OF
THE CNTRL AND ERN DAKOTAS AND THIS MAY BE ENOUGH FOR A POCKET OF
MODERATE INSTABILITY BY AFTERNOON. SCATTERED THUNDERSTORMS IN THE
MID-AFTERNOON WOULD MOST LIKELY OCCUR IN THIS AREA. THUNDERSTORMS
SHOULD ALSO INITIATE FURTHER SOUTH SOUTHWEST ACROSS WRN NEB AND NE
CO WHERE MODELS ARE FORECASTING STRONG LOW-LEVEL CONVERGENCE ALONG
THE SFC TROUGH. AS THUNDERSTORM COVERAGE INCREASES...SEVERAL LINEAR
MCS/S MAY GRADUALLY ORGANIZE WITH STORM COVERAGE EVENTUALLY FILLING
IN ALONG THE SFC TROUGH IN THE EVENING. MODEL FORECASTS HAVE BEEN
TOO FAST WITH THE UPPER-LEVEL TROUGH AND IT APPEARS THAT CONVECTION
WILL DEVELOP FURTHER WEST MORE CLOSELY ALIGNED WITH THE GFS
SOLUTION.
CONCERNING THE SEVERE POTENTIAL...A 70 KT MID-LEVEL JET OVER THE
FOUR CORNERS REGION IS FORECAST TO EJECT NEWD ACROSS THE NRN PLAINS
CREATING STRONG VERTICAL SHEAR PROFILES ACROSS THE REGION. VERTICAL
SHEAR IS ALSO FORECAST TO INCREASE IN THE CNTRL HIGH PLAINS IN THE
AFTERNOON. THE VERTICAL SHEAR SHOWN ON AFTERNOON FORECAST SOUNDINGS
SHOULD SUPPORT ISOLATED SUPERCELL DEVELOPMENT WITH THE GREATEST
POTENTIAL FOR SUPERCELLS OVER THE NRN PLAINS WHERE MORE INSTABILITY
SHOULD BE PRESENT. SUPERCELLS SHOULD HAVE A LARGE HAIL THREAT DUE TO
STEEP MID-LEVEL LAPSE RATES AND RELATIVELY COLD TEMPS ALOFT EVIDENT
ON FORECAST SOUNDINGS. A WIND DAMAGE THREAT MAY ALSO OCCUR AS LINE
SEGMENTS ORGANIZE ALONG THE SFC TROUGH IN THE EARLY EVENING. IF A
LINEAR MCS DEVELOPS IN THE VEERED LOW-LEVEL FLOW BEHIND THE SFC
TROUGH IN CNTRL SD AS SUGGESTED BY THE NAM...THE UNIDIRECTIONAL
BOUNDARY LAYER FLOW COULD RESULT IN AN ENHANCED WIND DAMAGE THREAT.
THE GREATEST SEVERE THREAT SHOULD BE CONCENTRATED IN THE 21Z TO 03Z
TIME FRAME WHEN INSTABILITY SHOULD BE STRONGEST ACROSS THE REGION.
..CNTRL AND ERN MT...
AN UPPER-LEVEL TROUGH OVER THE WEST COAST WILL MOVE EWD INTO THE
INTERMOUNTAIN WEST TODAY. STRONG LARGE-SCALE ASCENT ASSOCIATED WITH
THE UPPER-LEVEL TROUGH IS FORECAST TO OVERSPREAD THE NRN ROCKIES AND
NRN HIGH PLAINS. THIS WILL SUPPORT SCATTERED THUNDERSTORM
DEVELOPMENT NEAR A SFC LOW IN ECNTRL MT THIS AFTERNOON. STRONG
VERTICAL SHEAR PROFILES...COLD TEMPERATURES ALOFT AND STEEP
MID-LEVEL LAPSE RATES SHOWN ON FORECAST SOUNDINGS SHOULD SUPPORT AN
ISOLATED LARGE HAIL THREAT FOR A FEW HOURS LATE THIS AFTERNOON. THE
EXTENT OF THE THREAT SHOULD BE DEPENDENT ON HOW MUCH CLOUD COVER IS
PRESENT OVER ECNTRL MT AND THE RESULTANT SFC HEATING THAT TAKES
PLACE.
..SRN LA...
THE LATEST WATER VAPOR IMAGERY SHOWS A PLUME OF MOISTURE IN PLACE
ACROSS THE ERN GULF OF MEXICO. MODEL FORECASTS MOVE A CLUSTER OF
THUNDERSTORMS ASSOCIATED WITH THIS PLUME WWD INTO THE NRN GULF OF
MEXICO TODAY. THE NRN PART OF THE CONVECTIVE CLUSTER COULD AFFECT
THE COAST OF LA TONIGHT AS SUGGESTED BY THE GFS SOLUTION.
HOWEVER...THE GREATEST LOW-LEVEL SHEAR SHOULD REMAIN WELL OFFSHORE
AND AN ORGANIZED STORM THREAT IS NOT EXPECTED.
.BROYLES/GRAMS.. 09/23/2007
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