[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 121614
SWODY1
SPC AC 121612

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1112 AM CDT SAT AUG 12 2006

VALID 121630Z - 131200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM NERN CO ACROSS NRN PLAINS
INTO MN...

...SYNOPSIS...
WHILE RIDGING PREVAILS S OF 40N THE LARGE SCALE TROUGH WRN CANADA
INTO PAC NW WILL SHIFT EWD ACROSS NRN ROCKIES INTO NRN HIGH PLAINS
BY 12Z SUN.  S/WV ENERGY ROTATING THRU THE TROUGH CURRENTLY CROSSING
ID AND WRN MT WILL REACH HIGH PLAINS LATE TONIGHT. PRECEEDING THE
TROUGH A PLUME OF DEEP MONSOON MOISTURE IS SPREADING NEWD FROM
CENTRAL ROCKIES ACROSS THE NRN PLAINS TODAY.

AT THE SURFACE COLD FRONT CURRENTLY ACROSS WRN DAKOTAS AND THEN
WSWWD INTO SWRN WY AND NRN UT WILL ONLY SHIFT SLOWLY EWD THRU THE
AFTERNOON AS UPPER SUPPORT STILL WELL TO THE W.  30-40KT SLY LOW
LEVEL JET E OF FRONT CONTINUES TO PROVIDE A MOIST AND POTENTIALLY
VERY UNSTABLE AIR MASS NWD TO CANADIAN BORDER.

...NRN PLAINS...
THE COMBINATION OF WARM MID LEVEL TEMPERATURES AND THE MONSOON PLUME
OF MOISTURE WILL DELAY INITIATION OF SURFACE BASED SEVERE
THUNDERSTORMS UNTIL LATER THIS AFTERNOON/EVENING MUCH OF NRN PLAINS
AREA ALONG AND E OF COLD FRONT. SUFFICIENT ELEVATED INSTABILITY AND
SHEAR FOR MORE ISOLATED LARGE HAIL THIS AFTERNOON PRIOR TO THE 
EXPECTED MORE INTENSE DEVELOPMENT ONCE CAP HAS ERODED.

HOWEVER WITH DEWPOINTS MID 60S TO 70 F AND POTENTIAL FOR SURFACE
TEMPERATURES RISING THRU THE 90S F...CAP SHOULD WEAKEN SUFFICIENTLY
FOR SEVERE THUNDERSTORM DEVELOPMENT ALONG/AHEAD OF  COLD FRONT
CENTRAL ND/SD BY LATER THIS AFTERNOON. WITH DEEP LAYER SHEAR OF
30-40KT COUPLED WITH MLCAPES INCREASING TO 2500...SUPERCELLS ARE
LIKELY.  VERY LARGE HAIL WILL BE PRIMARY THREAT WITH ANY
SUPERCELL...HOWEVER SUFFICIENT LOW LCL/S ERN DAKOTAS/WRN MN BY LATE
THIS AFTERNOON FOR POSSIBLE TORNADOES AS WELL.

...NERN CO INTO NEB...
STRONG HEATING AND WEAKER SHEAR THIS AREA WILL RESULT IN A DEEPLY
MIXED BOUNDARY LAYER BY MID AFTERNOON. THUNDERSTORMS WILL DEVELOP
INITIALLY OVER HIGH TERRAIN AND IN CONVERGENCE ALONG COLD
FRONT...THEN PROPAGATE E/NE THRU THE EVENING.  PRIMARY THREAT GIVEN
THE EXPECTED STEEP LAPSE RATES AND HIGH BASES WILL BE DAMAGING
WINDS. ANY SEVERE HAIL WILL BE ASSOCIATED WITH ISOLATED SUPERCELLS
THAT COULD FORM PRIOR TO NIGHTFALL.

..HALES/JEWELL.. 08/12/2006