SWOD48
SPC AC 140821
DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0321 AM CDT FRI SEP 14 2007
VALID 171200Z - 221200Z
..DISCUSSION...
MEDIUM RANGE MODELS ARE IN REASONABLE AGREEMENT OF MOVING CLOSED
LOW...CURRENTLY LOCATED OFF THE CA/ORE COAST...ENEWD AS AN OPEN AND
SLIGHTLY NEGATIVELY TILTED TROUGH ACROSS THE ROCKIES AND INTO THE
NRN PLAINS ON MON/DAY 4. COLD FRONT ASSOCIATED WITH THIS SYSTEM
SHOULD STRENGTHEN SLY WINDS AND GRADUALLY INCREASE BOUNDARY LAYER
MOISTURE...THOUGH SURFACE RIDGING FROM THE NERN STATES SWWD INTO TX
SHOULD LIMIT RETURN OF QUALITY GULF MOISTURE. HOWEVER...SWLY WINDS
ALOFT AND APPROACHING TROUGH SHOULD STEEPEN MID LEVEL LAPSE RATES
AND PROVIDE SUFFICIENT INSTABILITY FOR THUNDERSTORMS. THE PRESENCE
OF THE UPPER TROUGH...STEEPER LAPSE RATES/INSTABILITY AND 50-60 KT
MID LEVEL WINDS INDICATES A THREAT FOR SEVERE STORMS ACROSS THE NRN
PLAINS MON AFTERNOON/NIGHT. THE MREF IS A BIT SLOWER THAN THE
EUROPEAN/GFS...SO THE SEVERE WEATHER AREA HAS BEEN SHIFTED SLIGHTLY
WWD FROM PREVIOUS OUTLOOK.
A SEVERE WEATHER THREAT MAY ALSO EXTEND EWD INTO THE UPPER MIDWEST
ON TUE/DAY 5...BUT DE-AMPLIFYING TROUGH AND POSSIBILITY OF STRONGER
UVV SHIFTING INTO CANADA PRECLUDES AN AREA ATTM. FROM WED/DAY 6-
FRI/DAY 8...DEEP LOW IS FORECAST TO EVOLVE OVER THE WEST...BUT
BLOCKING RIDGE OVER THE ERN HALF OF THE NATION WILL PREVENT THIS
SYSTEM FROM MOVING EWD.
.IMY.. 09/14/2007
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