SWODY2
SPC AC 111728
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1228 PM CDT FRI SEP 11 2009
VALID 121200Z - 131200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
AN UPPER RIDGE WILL BUILD NWD REACHING NRN CANADA RESULTING IN A REX
BLOCK TYPE PATTERN WITH A PAIR OF CLOSED UPPER LOWS LOCATED FARTHER
S OVER THE U.S. PLAINS STATES. MODELS ARE IN AGREEMENT WITH THIS
FLOW PATTERN SHOWING WWD MOVEMENT OF THE NRN CLOSED LOW INTO WY
UNDERGOING SOME DEEPENING AS IT TRACKS NWWD TOWARD SRN MT BY 12Z
SUNDAY. MEANWHILE...A WEAKER CLOSED LOW LOCATED OVER THE SOUTH
CENTRAL STATES SHOULD REMAIN NEARLY STATIONARY ON SATURDAY.
IN THE LOW LEVELS...A SURFACE LOW /ATTENDANT TO AN EMBEDDED IMPULSE
ROTATING NWD THROUGH THE ERN PERIPHERY OF THE SRN CLOSED LOW/ SHOULD
MOVE NWWD FROM THE UPPER TX COAST INTO CENTRAL TX. SURFACE FRONT
EXTENDING ESEWD THROUGH THE GULF OF MEXICO WILL MOVE NWD AND SHOULD
REACH THE LA COAST SATURDAY AFTERNOON...WHILE THE ERN EXTENT IS
EXPECTED TO REMAIN OVER THE NERN GULF.
...MIDDLE GULF COAST REGION...
A MARITIME/TROPICAL AIR MASS ALONG AND S OF SURFACE FRONT WILL BE
CHARACTERIZED BY VERY RICH LOW LEVEL MOISTURE...WITH SURFACE
DEWPOINTS IN THE LOW-MID 70S F AND FORECAST SOUNDINGS SUGGESTING PW
COMMONLY ABOVE 2 INCHES. DESPITE THIS AVAILABLE MOISTURE...WEAK
LAPSE RATES AND LACK OF STRONGER SURFACE HEATING DUE TO CLOUDINESS/
PRECIPITATION WILL RESULT IN MARGINAL INSTABILITY. EFFECTIVE BULK
SHEAR /30-35 KT/ OVER SRN LA TO NERN GULF WOULD SUPPORT SUPERCELLS.
HOWEVER...UNCERTAINTY FOR STORMS TO BECOME SURFACE BASED OVER INLAND
LOCATIONS REMAINS TOO MINIMAL TO INTRODUCE LOW SEVERE PROBABILITIES
FOR TORNADOES WHICH WOULD BE THE ONLY SEVERE WEATHER THREAT.
..PETERS.. 09/11/2009
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