DAY3SVR: Nws Storm Prediction Center Norman Ok

ACUS03 KWNS 110730
SWODY3
SPC AC 110728

DAY 3 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0228 AM CDT THU OCT 11 2012

VALID 131200Z - 141200Z

...THERE IS A SLGT RISK OF SVR TSTMS SAT INTO SAT NIGHT ACROSS PARTS
OF THE MID/UPPER MISSISSIPPI VALLEY INTO THE UPPER GREAT
LAKES...SOUTHWARD INTO THE SOUTHERN PLAINS...

...SYNOPSIS...
MODELS INDICATE THAT SPLIT BELTS OF STRONGER WESTERLIES WILL BEGIN
TO CONSOLIDATE ACROSS NORTH AMERICA DURING THIS FORECAST PERIOD...AS
THE REMNANT SOUTHERN STREAM CLOSED LOW CONTINUES ITS EAST
NORTHEASTWARD ACCELERATION OUT OF THE SOUTHWEST. VARIABILITY IS
INCREASING AMONG THE MODEL DATA CONCERNING THE EVOLUTION OF THIS
FEATURE...FROM WHICH A COUPLE OF MORE DISTINCT SMALLER SCALE
IMPULSES COULD EMERGE AS IT PROGRESSES EAST OF THE ROCKIES INTO THE
PLAINS/MISSISSIPPI VALLEY REGION. NAM/SREF APPEAR TO MAINTAIN THE
INITIAL CIRCULATION FORECAST TO REACH THE CENTRAL HIGH PLAINS BY 12Z
SATURDAY AS THE PRIMARY UPPER IMPULSE...AND ACCELERATE IT EASTWARD
INTO THE UPPER GREAT LAKES BY 12Z SUNDAY...MUCH AS GENERALLY HAS
BEEN INDICATED BY MEDIUM RANGE GUIDANCE THE PAST FEW DAYS.
HOWEVER...THE GFS SUGGESTS THAT A DISTINCT SECONDARY
IMPULSE...TRAILING TO THE SOUTHWEST...MAY BECOME THE MORE PROMINENT
IMPULSE SATURDAY...AS IT LIFTS EAST OF THE SOUTHERN ROCKIES...ACROSS
THE SOUTH CENTRAL HIGH PLAINS INTO THE MIDDLE MISSISSIPPI VALLEY.
ECMWF ALSO NOW IS MORE SUGGESTIVE THAT STRONGER MID-LEVEL FORCING
MAY DEVELOP SOUTH OF THE INITIAL IMPULSE...BUT NORTH OF THAT OF THE
GFS.

REGARDLESS...ALL GUIDANCE INDICATES THE CONTINUED DEVELOPMENT OF A
SUB-1000 MB SURFACE LOW...GENERALLY EAST OF THE MIDDLE MISSOURI
VALLEY TOWARD THE GREAT LAKES REGION. WITHIN THE WARM SECTOR OF
THIS FEATURE...AND SOUTHWARD AHEAD OF THE TRAILING COLD FRONT/DRY
LINE ADVANCING EASTWARD THROUGH THE SOUTHERN PLAINS...A BROAD
SOUTHERLY 850 MB JET IS FORECAST TO STRENGTHEN FROM 50-70
KT...BENEATH A 70+ KT SOUTHWESTERLY 500 MB JET. THIS WILL
CONTRIBUTE TO THE NORTHWARD ADVECTION OF SEASONABLY HIGH MOISTURE
CONTENT AIR /PRECIPITABLE WATER UP AROUND 1.5+ INCHES/...WITH 60F+
SURFACE DEW POINTS AS FAR NORTH AS PORTIONS OF THE UPPER MISSISSIPPI
VALLEY.

DESTABILIZATION SHOULD BE SUFFICIENT TO SUPPORT WIDESPREAD
CONVECTIVE DEVELOPMENT...INCLUDING PERHAPS CONSIDERABLE POTENTIAL
FOR SEVERE THUNDERSTORMS FROM PORTIONS OF THE UPPER MISSISSIPPI
VALLEY SOUTHWARD THROUGH THE SOUTHERN PLAINS.

...UPPER MISSISSIPPI VALLEY INTO THE SOUTHERN PLAINS...
GIVEN THE STRENGTH OF THE WARM SECTOR DEEP LAYER MEAN FLOW
FIELDS/SHEAR AND FORCING FOR UPWARD VERTICAL MOTION...SEVERE
POTENTIAL ON SATURDAY MAY ULTIMATELY BE HIGHER THAN CURRENTLY
INDICATED BY THE SLIGHT RISK CATEGORICAL OUTLOOK. CONDITIONS MOST
SUPPORTIVE OF THIS POTENTIAL STILL APPEAR MOST PROBABLE TO EVOLVE
FROM PARTS OF EASTERN NEBRASKA AND KANSAS THROUGH CENTRAL AND
NORTHERN MISSOURI...IOWA AND ADJACENT PORTIONS OF SOUTHERN
MINNESOTA...SOUTHWEST WISCONSIN AND NORTHWESTERN ILLINOIS.
HOWEVER...UNCERTAINTY LINGERS CONCERNING THE DEGREE OF WARM SECTOR
BOUNDARY LAYER DESTABILIZATION THAT MAY OCCUR...DUE TO THE
POSSIBILITY OF CONSIDERABLE EARLY PERIOD CONVECTION WHICH MAY SLOW
OR INHIBIT INSOLATION. COUPLED WITH THE AFOREMENTIONED MODEL
VARIABILITY...TOO MUCH UNCERTAINTY STILL EXISTS FOR HIGHER SEVERE
PROBABILITIES. BUT A SIGNIFICANT CONVECTIVE DAMAGING WIND EVENT
APPEARS A POSSIBILITY. IT MAY NOT BE OUT OF THE QUESTION THAT
CONDITIONS COULD BECOME FAVORABLE FOR TORNADIC SUPERCELLS.

..KERR.. 10/11/2012

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.