[SWODY1] SWODY1

Thu Apr 6 06:04:36 UTC 2006

ACUS01 KWNS 060601
SWODY1
SPC AC 060600

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0100 AM CDT THU APR 06 2006

VALID 061200Z - 071200Z

...THERE IS A MDT RISK OF SVR TSTMS THIS AFTN AND EARLY EVE ACROSS
PARTS OF ERN NEB/ERN KS/PARTS OF ERN OK/WRN IA/WRN MO AND NW
AR...WHERE WIDESPREAD SEVERE THUNDERSTORMS APPEAR
POSSIBLE...INCLUDING RISK FOR VERY LARGE HAIL/DAMAGING WINDS AND A
FEW TORNADOES....

...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK AREA
ACROSS MUCH OF THE EAST CENTRAL PLAINS INTO MIDDLE MS VLY....

COLD SOUTHERN BRANCH TROUGH OVER THE INTERMOUNTAIN WEST IS OUT OF
PHASE WITH THE NORTHERN STREAM...AND NEXT UPSTREAM IMPULSE IS
PROGGED TO REMAIN WELL WEST OF THE PACIFIC COAST THROUGH AT LEAST
12Z FRIDAY.  HOWEVER...THE SYSTEM IS SLOWLY PROGRESSING EASTWARD
INTO THE ROCKIES...TO THE SOUTH OF A NORTHERN BRANCH RIDGE...WHICH
WILL PERSIST TO THE LEE OF THE CANADIAN ROCKIES.  THOUGH THERE IS
SOME CONCERN ABOUT THE RATE OF PROGRESSION OF THE TROUGH TO THE EAST
OF THE U.S. ROCKIES...MODELS CONTINUE TO INDICATE THAT EMBEDDED
CIRCULATION WILL REFORM SOUTHEASTWARD INTO EASTERN COLORADO EARLY
TODAY...THEN INTO THE CENTRAL PLAINS BY THE END OF THE FORECAST
PERIOD.  THIS IS PROGGED TO OCCUR AS A STRONG MID-LEVEL IMPULSE/JET
STREAK ROTATES AROUND ITS SOUTHERN/EASTERN PERIPHERY...ACROSS THE
CENTRAL PLAINS DURING THE DAY TODAY...THROUGH THE MID/LOWER MISSOURI
VALLEY BY LATE TONIGHT.

IN RESPONSE TO EVOLVING UPPER FLOW PATTERN...PRIMARY SURFACE CYCLONE
IS PROGGED TO FORM OVER CENTRAL NEBRASKA...THEN SLOWLY DEEPEN
THROUGH THE DAY.  SYSTEM IS PROGGED TO BECOME OCCLUDED LATE THIS
AFTERNOON AND TONIGHT...BUT REMAIN OVER THE NORTH CENTRAL PLAINS AS
WEAK TRIPLE POINT WAVE SHIFTS EASTWARD TOWARD THE SOUTHERN GREAT
LAKES REGION.

...CENTRAL STATES...
CONSIDERABLE CLOUD COVER AND SCATTERED CONVECTIVE DEVELOPMENT SEEM
LIKELY TO IMPEDE BOUNDARY LAYER DESTABILIZATION THROUGH MUCH OF THE 
OZARKS INTO THE MIDDLE MISSISSIPPI VALLEY TODAY.  HOWEVER...
MID-LEVEL DRY SLOT IS EXPECTED TO ALLOW INSOLATION IN AT LEAST A
NARROW CORRIDOR AHEAD OF COLD FRONT/DRY LINE TRAILING SOUTHWARD FROM
SURFACE LOW CENTER.  BY MID DAY...BOUNDARY IS EXPECTED ROUGHLY WEST
OF GRAND ISLAND NEB/MANHATTAN AND WICHITA KS INTO CENTRAL
OKLAHOMA...PRECEDED BY TONGUE OF 60F+ SURFACE DEW POINTS.  AS
MID-LEVEL THERMAL TROUGH TAKES ON INCREASING NEGATIVE
TILT...MID-LEVEL CAPPING IS EXPECTED TO BE BROKEN...PERHAPS AS EARLY
AS THE 18-21Z TIME FRAME.

RAPID DEVELOPMENT OF A BROKEN SQUALL LINE APPEARS LIKELY IN AN
ENVIRONMENT WITH STEEP LAPSE RATES AND MODERATELY STRONG CAPE OF
1500-2000 J/KG...AND SHEAR IN EXIT REGION OF 90+ KT 500 MB JET
NOSING ACROSS OKLAHOMA WILL BE SUFFICIENT FOR SUPERCELLS.  VERY
LARGE HAIL/DAMAGING WIND GUSTS WILL LIKELY ACCOMPANY STRONGEST
CONVECTION.  TORNADO POTENTIAL IS MORE UNCERTAIN...MAINLY ACROSS
EASTERN KANSAS INTO WESTERN MISSOURI...WHERE DEEP LAYER SOUTHERLY
FLOW WILL EXIST.  FARTHER TO THE NORTH...TO THE EAST OF SURFACE LOW
CENTER...EASTERLY LOW-LEVEL FLOW WILL CONTRIBUTE TO SIZABLE
CLOCKWISE CURVING LOW-LEVEL HODOGRAPHS BENEATH MODERATE STRONG
SOUTHERLY UPPER FLOW.  THIS SHOULD ENHANCE POTENTIAL FOR TORNADOES
ACROSS PARTS OF EASTERN NEBRASKA INTO WESTERN IOWA...PERHAPS EXTREME
NORTHWEST MISSOURI.

A SECONDARY AREA OF SIGNIFICANT CONVECTIVE DEVELOPMENT APPEARS
POSSIBLE WHERE MID-LEVEL JET STREAK NOSES OVER DRY LINE ACROSS
NORTHEAST OKLAHOMA.  THIS SEEMS POSSIBLE BY 21-22Z.  MODELS SUGGEST
STRONG MID-LEVEL FLOW ACROSS THIS REGION WILL VEER TO A MORE
WESTERLY COMPONENT...WHICH MAY FAVOR MORE DISCRETE SUPERCELL
DEVELOPMENT IN ENVIRONMENT WITH CAPE AROUND 2000 J/KG. VEERING OF
WINDS WITH HEIGHT BENEATH 30 TO 50 KT SOUTHERLY LOW-LEVEL JET MAY
NOT BECOME STRONG...BUT SHEAR IS EXPECTED TO BE SUFFICIENT FOR
TORNADIC ACTIVITY.  ISOLATED STRONG TORNADOES SEEM POSSIBLE AS
ACTIVITY DEVELOPS NORTHEASTWARD INTO THE OZARK PLATEAU.

SEVERE THREAT MAY CONTINUE THROUGH THE EVENING INTO MUCH OF THE
MIDDLE MISSISSIPPI VALLEY.  HOWEVER...INTENSITY/COVERAGE OF SEVERE
THREAT IS EXPECTED TO DIMINISH SIGNIFICANTLY BY LATE EVENING...AS
EVOLUTION OF LARGE-SCALE PATTERN DOES NOT APPEAR LIKELY TO SUPPORT
SIGNIFICANT EASTWARD DESTABILIZATION DURING THIS FORECAST PERIOD.

..KERR/CROSBIE.. 04/06/2006