SWODY1
SPC AC 230531
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1131 PM CST THU NOV 22 2007
VALID 231200Z - 241200Z
..NO SVR TSTM AREAS FORECAST...
..SYNOPSIS...
MODELS INDICATE THAT A SPLIT IN THE POLAR STREAM WILL PERSIST
THROUGH THIS FORECAST PERIOD...DOWNSTREAM OF A SHARP UPPER RIDGE
GRADUALLY SHIFTING INTO PACIFIC COASTAL AREAS. THE RIDGE IS PROGGED
TO BEGIN WEAKENING...HOWEVER...AS A SIGNIFICANT SHORT WAVE TROUGH
OVERTAKES IT...ADVANCING INTO BRITISH COLUMBIA/PACIFIC NORTHWEST
COASTAL AREAS TOWARD 12Z SATURDAY. AT THE SAME TIME...A DOWNSTREAM
NORTHERN BRANCH TROUGH ACROSS THE NORTHEASTERN QUARTER OF THE NATION
IS EXPECTED TO BEGIN TO LOSE AMPLITUDE. BUT...A STRONG IMPULSE
DIGGING IN THE SOUTHERN STREAM IS FORECAST TO BEGIN SUPPORTING THE
EVOLUTION OF A MID-LEVEL CLOSED LOW OVER THE NORTHWESTERN MEXICAN
PLATEAU. AS THIS OCCURS...UPPER RIDGING WILL BUILD ACROSS THE
EASTERN GULF OF MEXICO AND FLORIDA PENINSULA INTO THE SOUTHEASTERN
STATES...WITH A MOISTENING SOUTHWESTERLY MID-LEVEL FLOW DEVELOPING
ACROSS THE LOWER RIO GRANDE VALLEY INTO THE WESTERN/CENTRAL GULF
STATES.
IN RESPONSE TO THE EVOLVING UPPER PATTERN...MODELS INDICATE THAT ONE
COLD SURFACE RIDGE WILL DEVELOP SOUTHEASTWARD INTO THE GREAT
BASIN/CENTRAL ROCKIES...AS THE CENTER OF ANOTHER LARGER RIDGE SHIFTS
FROM THE MISSOURI OZARKS TO THE LEE OF THE CENTRAL APPALACHIANS.
AND...A GENERALLY STABLE THERMODYNAMIC STRATIFICATION WILL PERSIST
OVER MUCH OF THE COUNTRY...WITH LOW CONVECTIVE POTENTIAL.
..SOUTHERN PLATEAU/FOUR CORNERS STATES...
IN RESPONSE TO FORCING/DESTABILIZATION WITH AN INITIAL DIGGING SHORT
WAVE IMPULSE...CONVECTIVE DEVELOPMENT...INCLUDING SCATTERED WEAK
THUNDERSTORMS...IS UNDERWAY NEAR THE FOUR CORNERS REGION.
AND...THIS MAY PERSIST INTO THE BEGINNING OF THE FORECAST
PERIOD...BEFORE UPPER SYSTEM PROGRESSES INTO CONFLUENT FLOW EAST OF
THE ROCKIES...AND WEAKENS. IN ITS WAKE...THE NEXT IMPULSE IS
PROGGED TO DIG SOUTH OF THE SIERRA NEVADA THROUGH THE LOWER COLORADO
VALLEY/NORTHERN GULF OF CALIFORNIA AND SONORA BY 12Z SATURDAY.
ADDITIONAL WEAK AFTERNOON STORMS APPEAR POSSIBLE ACROSS EASTERN
ARIZONA NEAR/SOUTH OF THE MOGOLLON RIM...BUT BETTER POTENTIAL SEEMS
LIKELY TO ACCOMPANY STRONGER FORCING LATE FRIDAY NIGHT INTO EARLY
SATURDAY ACROSS NORTHERN SONORA INTO THE MOUNTAINS OF SOUTHEASTERN
ARIZONA.
..SOUTH CENTRAL/SOUTHERN TEXAS...
DOWNSTREAM OF AMPLIFYING SOUTHERN BRANCH TROUGH...A SOUTHERLY RETURN
FLOW OF LOW-LEVEL MOISTURE IS PROGGED DURING THE LATTER HALF OF THE
FORECAST PERIOD...ABOVE A LINGERING COLD/STABLE BOUNDARY LAYER. IN
CONJUNCTION WITH LARGE-SCALE ASCENT ASSOCIATED WITH STRENGTHENING
LOW/MID-LEVEL WARM ADVECTION...FORECAST SOUNDINGS INDICATE THAT
DESTABILIZATION SUPPORTIVE OF SCATTERED WEAK THUNDERSTORM ACTIVITY
WILL OCCUR. THIS IS MOSTLY EXPECTED DURING THE 24/03-12Z TIME
FRAME...NORTH OF STRENGTHENING MID-LEVEL CAP SPREADING INTO PARTS OF
DEEP SOUTH TEXAS.
..FLORIDA PENINSULA...
GUIDANCE IS UNCLEAR CONCERNING CONVECTIVE POTENTIAL ALONG/AHEAD OF
SURFACE FRONT EXPECTED TO ADVANCE THROUGH THE SOUTHERN PENINSULA
THIS AFTERNOON. WHILE THE POSSIBILITY APPEARS TO EXIST FOR
SCATTERED FAIRLY DEEP CONVECTION...PERHAPS A BAND OF SHOWERS...IT
CURRENTLY SEEMS MOST PROBABLE THAT A RELATIVELY WARM MID-LEVEL AIR
MASS WILL SUPPRESS THUNDERSTORM ACTIVITY OVER INLAND AREAS.
HOWEVER...A FEW THUNDERSTORMS ARE POSSIBLE IN SLIGHTLY GREATER
BOUNDARY LAYER MOISTURE OVER COASTAL WATERS.
.KERR.. 11/23/2007
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