DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 161953
SWODY1
SPC AC 161950

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0250 PM CDT WED SEP 16 2009

VALID 162000Z - 171200Z

...NO SVR TSTM AREAS FORECAST...

...SERN STATES...

THIS AFTERNOON SEVERAL NW-SE ORIENTED CONVERGENCE BOUNDARIES EXTEND
FROM A SURFACE LOW IN SRN AR SEWD THROUGH MS...TN...AL AND GA.
NUMEROUS CLOUD BREAKS HAVE PROMOTED DESTABILIZATION OF THE MOIST
WARM SECTOR WITH 1000-1500 J/KG MLCAPE OVER THE CNTRL AND SRN GULF
COASTAL STATES. STRONGEST UPDRAFTS HAVE DEVELOPED ACROSS CNTRL AND
SRN AL ALONG WRN FRINGE OF SUBTROPICAL MOIST PLUME WHERE UPDRAFTS
ARE EMBEDDED WITHIN 40 KT SWLY UPPER FLOW AND 25-30 KT SWLY DEEP
LAYER SHEAR. OCCASIONAL UPDRAFT ROTATION CONTINUES TO BE OBSERVED
WITH STORMS LIFTING NWD THROUGH WARM SECTOR ACROSS AL. VWP DATA
INDICATE LOW LEVEL HODOGRAPHS REMAIN RELATIVELY SMALL AND THIS WILL
CONTINUE TO BE A LIMITING FACTOR FOR A MORE ROBUST SEVERE THREAT.
HOWEVER...IT APPEARS THAT VEERING WIND PROFILES WITHIN THE LOWEST 2
KM ARE RESULTING IN SUFFICIENT VORTICITY FOR A THREAT OF LOW LEVEL
MESOCYCLONES AND POSSIBLY ANOTHER BRIEF TORNADO OR TWO. THE THREAT
EITHER HAS PEAKED OR WILL LIKELY PEAK WITHIN THE NEXT COUPLE HOURS
FOLLOWED BY A GRADUAL DECREASE IN SEVERE POTENTIAL AS THE BOUNDARY
LAYER BEGINS TO STABILIZE.

..DIAL/COOK.. 09/16/2009

.PREV DISCUSSION... /ISSUED 1052 AM CDT WED SEP 16 2009/

LITTLE OVERALL CHANGE IN LARGE SCALE BLOCKING PATTERN ACROSS THE
CONUS. DUAL CUT-OFF LOWS TRAPPED UNDER THE BLOCKING HIGH OVER NRN
HIGH PLAINS ARE FORECAST TO DRIFT SWD...ONE INTO CENTRAL AZ AND THE
OTHER OVER SWRN AR BACK INTO ERN TX.

CONDITIONS IN WARM SECTOR...CENTRAL GULF STATES HAVE CHANGED LITTLE
IN THE PAST SEVERAL DAYS...WITH A VERY MOIST/TROPICAL AIR MASS IN
PLACE AND JUST ENOUGH SHEAR BEING GENERATED BY THE CUT-OFF LOW TO
MAINTAIN A NON-ZERO THREAT OF ROTATING PRIMARILY DIURNAL
THUNDERSTORMS. THUS WILL CONTINUE WITH BOTH A LOW PROBABILITY OF
ISOLATED/BRIEF TORNADOS AND WET MICROBURSTS THIS AFTERNOON/EARLY
EVENING.

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