DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 090729
SWODY3
SPC AC 090728

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0228 AM CDT TUE OCT 09 2012

VALID 111200Z - 121200Z

...SYNOPSIS...
AS A STRONG ZONAL BELT OF FLOW EXTENDING ACROSS THE MID LATITUDE
PACIFIC BEGINS TO APPROACH THE PACIFIC NORTHWEST COAST...THE CLOSED
LOW WITHIN A REMNANT WEAKER BRANCH OF WESTERLIES... EXTENDING OFF
THE PACIFIC INTO THE SOUTHWESTERN STATES...APPEARS LIKELY TO BEGIN A
SLOW EASTWARD ACCELERATION. AS THIS FEATURE PROGRESSES ACROSS
SOUTHERN CALIFORNIA THROUGH THE SOUTHERN GREAT BASIN/SOUTHERN
PLATEAU REGION DURING THIS PERIOD...SOME AMPLIFICATION OF DOWNSTREAM
RIDGING WITHIN THIS SOUTHERN STREAM IS FORECAST ACROSS THE CENTRAL
AND SOUTHERN PLAINS. AT THE SAME TIME...MOISTURE WILL CONTINUE TO
ADVECT INLAND ON SOUTHERLY LOW-LEVEL FLOW OFF THE GULF OF
MEXICO...AS ANOTHER COLD SURFACE RIDGE MIGRATES SOUTHWARD ACROSS THE
NORTH CENTRAL STATES...IN THE WAKE OF A LOW AMPLITUDE NORTHERN
STREAM SHORT WAVE TROUGH DIGGING ACROSS THE UPPER GREAT LAKES. BY
THE END OF THE PERIOD...A CONSOLIDATING LOW-LEVEL BAROCLINIC ZONE IS
EXPECTED TO EXTEND IN EAST-WEST FASHION ACROSS THE CENTRAL PLAINS
INTO THE LOWER OHIO VALLEY.

COLD AIR ALOFT ASSOCIATED WITH THE UPPER LOW...AND LOW-LEVEL
THERMAL/MOISTURE ADVECTION EAST OF THE ROCKIES...ARE EXPECTED TO
CONTRIBUTE TO AT LEAST WEAK DESTABILIZATION...WITH THE RISK OF
SCATTERED THUNDERSTORM ACTIVITY OVER A BROAD AREA THURSDAY AND
THURSDAY NIGHT. THIS PROBABLY WILL INCLUDE PORTIONS OF SOUTHERN
CALIFORNIA AND MUCH OF THE CENTRAL/SOUTHERN INTERMOUNTAIN
REGION...AS WELL AS THE SOUTHERN HIGH PLAINS INTO THE CENTRAL
PLAINS/MIDDLE MISSISSIPPI AND LOWER OHIO VALLEYS.

...SRN HIGH PLAINS INTO CNTRL PLAINS/MIDDLE MS VALLEY...
UNCERTAINTY EXISTS CONCERNING POTENTIAL FOR EARLY PERIOD CLOUD COVER
AND CONVECTION...AND ITS POTENTIALLY STABILIZING INFLUENCE. BUT
GUIDANCE IS SUGGESTIVE THAT VERTICAL SHEAR AND BOUNDARY LAYER
INSTABILITY COULD BECOME MARGINALLY SUFFICIENT FOR STRONG/SEVERE
STORM DEVELOPMENT ALONG THE SURFACE TROUGH/DRY LINE ACROSS THE
SOUTHERN HIGH PLAINS LATE THURSDAY AFTERNOON. SOMEWHAT GREATER
BOUNDARY LAYER DESTABILIZATION APPEARS POSSIBLE NEAR THE NOSE OF
WARMER ELEVATED MIXED LAYER AIR...AHEAD OF THE COLD FRONT...ACROSS
PARTS OF SOUTHERN KANSAS. HOWEVER...MID/ UPPER FORCING FOR UPWARD
VERTICAL MOTION APPEARS LIKELY TO REMAIN WEAK...AND THERE MAY BE A
TENDENCY FOR THE FRONT TO UNDERCUT ANY CONVECTION DEVELOPING ALONG
IT. PRIMARY CONVECTIVE DEVELOPMENT MAY NOT OCCUR UNTIL THURSDAY
NIGHT...AS CONFLUENT FLOW ON THE WESTERN AND NORTHERN PERIPHERY OF
LOW-LEVEL RIDGING STRENGTHENS ...BOTH ACROSS PARTS OF THE SOUTHERN
HIGH PLAINS...AND NORTH OF THE SURFACE FRONT...MAINLY ACROSS PARTS
OF KANSAS AND MISSOURI... PERHAPS INTO THE LOWER OHIO VALLEY. IT IS
NOT OUT OF THE QUESTION THAT THERMODYNAMIC PROFILES COULD BECOME
CONDUCIVE TO AT LEAST SOME SEVERE HAIL.

..KERR.. 10/09/2012

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