SWODY1
SPC AC 280523
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1123 PM CST FRI NOV 27 2009
VALID 281200Z - 291200Z
...NO SVR TSTM AREAS FORECAST...
...SYNOPSIS...
A CLOSED LOW...WHICH HAS EVOLVED FROM A SIGNIFICANT SHORT WAVE
TROUGH SPLITTING OFF THE MAIN POLAR JET...CONTINUES TO DEVELOP AND
DIG SOUTHWARD THROUGH CENTRAL/SOUTHERN CALIFORNIA. THIS PROCESS IS
PROGGED TO CONTINUE THROUGH MUCH OF THIS FORECAST PERIOD...AS UPPER
RIDGING GRADUALLY BUILDS NORTHWARD ACROSS THE PACIFIC NORTHWEST AND
CANADIAN ROCKIES...AND MODELS INDICATE THAT THE CIRCULATION CENTER
WILL REACH NORTHERN BAJA BY EARLY SUNDAY. BEFORE THIS OCCURS...AN
INITIAL SIGNIFICANT EMBEDDED IMPULSE APPEARS LIKELY TO PIVOT AROUND
ITS EASTERN/NORTHEASTERN PERIPHERY...INTO THE SOUTHERN PLATEAU.
AT THE SAME TIME...BROAD TROUGHING...WITHIN A BELT OF WESTERLIES
EMANATING FROM THE SUBTROPICAL EASTERN PACIFIC...IS EXPECTED TO LIFT
THROUGH THE CENTRAL/EASTERN GULF COAST STATES...AS A DEEP CLOSED LOW
AND SURFACE CYCLONE ASSOCIATED WITH THE POLAR STREAM LIFT THROUGH
THE CANADIAN MARITIMES. IN THE WAKE OF THE TRAILING
FEATURE...BOUNDARY LAYER MOISTENING OVER THE WESTERN GULF OF
MEXICO...AND A NORTHWARD RETURN FLOW INTO THE SOUTHERN PLAINS/ OZARK
PLATEAU...MAY COMMENCE. HOWEVER...SHORT WAVE RIDGING/ MID-LEVEL
HEIGHT RISES DOWNSTREAM OF THE SOUTHWESTERN CLOSED LOW SHOULD
INHIBIT CONVECTIVE POTENTIAL.
...SOUTHWESTERN U.S...
MID-LEVEL COOLING/LIFT ASSOCIATED WITH THE DIGGING CLOSED LOW MAY
BEGIN TO IMPACT THE LOS ANGELES BASIN PRIOR TO 12Z THIS
MORNING...ACCOMPANIED BY THE RISK FOR ISOLATED TO WIDELY SCATTERED
THUNDERSTORM ACTIVITY. THUNDERSTORMS WILL THEN REMAIN POSSIBLE
THROUGH MUCH OF THE DAY ALONG AND INLAND OF SOUTHERN CALIFORNIA
COASTAL AREAS.
WITH TIME...DIFFERENTIAL THERMAL ADVECTION AND LARGE-SCALE FORCING
FOR UPWARD VERTICAL MOTION ARE EXPECTED TO CONTRIBUTE TO
DESTABILIZATION ACROSS THE SOUTHERN PLATEAU INTO THE SOUTHERN
ROCKIES. WHILE GUIDANCE IS SUGGESTIVE THAT MOISTENING MAY BE
SOMEWHAT MODEST...AT LEAST SCATTERED THUNDERSTORMS APPEAR
PROBABLE...PARTICULARLY ACROSS THE LOWER CENTRAL DESERTS INTO THE
MOUNTAINS OF CENTRAL/SOUTHEASTERN ARIZONA BY LATE AFTERNOON. STORMS
MAY PERSIST INTO THE EVENING...PERHAPS THE OVERNIGHT HOURS...BEFORE
DECREASING IN NUMBER/COVERAGE. ALTHOUGH COOLING THERMODYNAMIC
PROFILES COULD BECOME CONDUCIVE TO SOME HAIL IN STRONGER STORMS AT
PEAK INTENSITY...ACTIVITY IS EXPECTED TO REMAIN GENERALLY WELL BELOW
SEVERE CRITERIA.
..KERR.. 11/28/2009
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