SWODY1
SPC AC 011553
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1053 AM CDT MON SEP 01 2008
VALID 011630Z - 021200Z
...THERE IS A SLGT RISK OF SVR TSTMS THROUGH TONIGHT ACROSS THE N
CENTRAL GULF COAST...
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO EARLY
TONIGHT FOR PARTS OF THE CENTRAL AND NRN PLAINS...
...N CENTRAL GULF COAST THROUGH TONIGHT...
HURRICANE GUSTAV WILL CONTINUE TO MOVE SLOWLY NWWD AND WEAKEN FROM S
CENTRAL LA TODAY INTO WRN LA BY LATE TONIGHT. THE ENVELOPE OF
SUFFICIENTLY STRONG LOW-MID LEVEL FLOW/SHEAR FOR SUPERCELLS WILL
COVER AREAS FROM NEAR I-20 TODAY IN LA/MS ESEWD INTO THE WRN FL
PANHANDLE. A SOMEWHAT COOLER/DRIER LOW-LEVEL AIR MASS WILL LIKELY
PERSIST THROUGH THE DAY TO THE NW OF THE STORM CENTER...WHILE THE
RICHEST BOUNDARY LAYER MOISTURE /DEWPOINTS OF 76-78 F/ AND WARMEST
TEMPERATURES /LOW 80S/ ARE EXPECTED TO SPREAD SLOWLY WWD FROM THE FL
PANHANDLE/SRN AL INTO SRN MS AND SE LA AS THE HURRICANE MOVES
FARTHER W/NW. THE GREATER THREAT FOR TORNADOES IS EXPECTED IN THE
NARROW CORRIDOR OF RICHER MOISTURE/GREATER INSTABILITY THROUGH THIS
AFTERNOON...ABOUT 75-150 MI E OF THE STORM CENTER.
...NRN AND CENTRAL PLAINS...
A SURFACE LOW NEAR THE CENTRAL SD/ND BORDER WILL DEVELOP NNEWD TODAY
ALONG A SHARP BAROCLINIC ZONE TOWARD NE ND/NW MN BY LATE
AFTERNOON...IN ADVANCE OF A LEAD SHORTWAVE TROUGH. THE PRIMARY MID
LEVEL WAVE WILL EJECT NEWD FROM THE NRN GREAT BASIN THIS MORNING TO
THE NRN HIGH PLAINS TONIGHT...WHILE THE ASSOCIATED SURFACE COLD
FRONT MOVES SEWD ACROSS THE NRN/CENTRAL PLAINS. REGIONAL 12Z
SOUNDINGS FROM NEB NWD TO THE DAKOTAS SHOW RELATIVELY MOIST PROFILES
AND MODEST MID LEVEL LAPSE RATES OF LESS THAN 7 C/KM WITHIN THE
MONSOONAL MOISTURE PLUME SPREADING NEWD FROM THE ROCKIES.
STILL...BOUNDARY LAYER DEWPOINTS IN THE MID-UPPER 60S AND AFTERNOON
TEMPERATURES OF 85-90 F WILL SUPPORT A NARROW CORRIDOR OF 1000-1500
J/KG MLCAPE IN ADVANCE OF THE FRONT FROM SD INTO ERN ND/NW MN.
A BAND OF THUNDERSTORMS WILL LIKELY DEVELOP ALONG THE COLD FRONT AND
SPREAD NNEWD THIS AFTERNOON INTO THIS EVENING. FORECAST SOUNDINGS
SUPPORT THE POTENTIAL FOR EMBEDDED SUPERCELLS AND/OR BOW ECHOES
WITHIN THE LARGER CONVECTIVE BAND PARALLELING THE FRONT. DAMAGING
WINDS SHOULD BE THE MAIN THREAT GIVEN THE INCREASING LOW-MID LEVEL
FLOW AND MODEST LAPSE RATES. LOW-LEVEL SHEAR WILL BE SUFFICIENT FOR
A TORNADO THREAT NEAR AND NE OF THE SURFACE WAVE ON THE FRONT IN
ND...IF STORMS CAN STAY SURFACE-BASED ALONG THE FRONT.
ANOTHER BAND/CLUSTER OF STORMS WILL LIKELY FORM LATE THIS
AFTERNOON/EVENING FARTHER S INTO THE HIGH PLAINS...IN ASSOCIATION
WITH THE APPROACH OF THE PRIMARY MID LEVEL WAVE AND FRONTAL SURGE.
AN INITIAL FRONTAL SURGE FROM WY INTO THE NEB PANHANDLE SUGGESTS
THAT INSTABILITY WILL BE MORE LIMITED IN E/SE WY THAN EXPECTED
EARLIER. THUS...THE PRIMARY SEVERE THREAT HAS BEEN SHIFTED EWD FROM
WY INTO NEB.
..THOMPSON/GRAMS.. 09/01/2008
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