[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 151633
SWODY1
SPC AC 151631

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1131 AM CDT THU JUN 15 2006

VALID 151630Z - 161200Z

...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON INTO EARLY
TONIGHT ACROSS THE CENTRAL AND NRN PLAINS....

...CENTRAL PLAINS THIS AFTERNOON/EARLY TONIGHT...
A BROAD MID LEVEL TROUGH IS MOVING SLOWLY EWD OVER THE INTERMOUNTAIN
WEST.  THE NRN PORTION OF THE TROUGH IS COMPRISED OF A CLOSED LOW
OVER NW MT/SRN ALBERTA...WHILE A SEPARATE SHORTWAVE TROUGH IS MOVING
 EWD FROM THE SRN GREAT BASIN TOWARD THE FOUR CORNERS. AT THE
SURFACE...A WEAK SURFACE COLD FRONT FROM ERN CO TO NW KS/CENTRAL NEB
AND THE WRN/CENTRAL DAKOTAS WILL DRIFT SLOWLY EWD/SEWD TODAY.  A
SURFACE CYCLONE ALONG THE FRONT IN N CENTRAL NEB THIS MORNING SHOULD
BECOME MORE DIFFUSE WITH TIME AS SURFACE PRESSURES FALL ACROSS SE
CO/NE NM IN RESPONSE TO THE WAVE APPROACHING THE FOUR CORNERS. THE
BAROCLINIC ZONE WILL PROVIDE THE PRIMARY FOCUS FOR THUNDERSTORM
DEVELOPMENT LATE TODAY INTO TONIGHT.

SURFACE ANALYSES AND 12Z SOUNDINGS REVEAL RATHER POOR LOW-LEVEL
MOISTURE AND A VERY WARM ELEVATED MIXED LAYER OVER MUCH OF THE
CENTRAL PLAINS.  RICHER LOW-LEVEL MOISTURE IS SPREADING NWWD ACROSS
TX...BUT IT APPEARS THAT VERTICAL MIXING WILL PARTIALLY COUNTERACT
ADVECTION AT THE SURFACE BY MID-LATE AFTERNOON...AND THE 60+
DEWPOINTS APPEAR UNLIKELY TO REACH THE LEE TROUGH AND BAROCLINIC
ZONE THIS AFTERNOON ACROSS THE HIGH PLAINS.  INSTEAD...SURFACE
TEMPERATURES OF 95-100 F AND ASCENT ALONG THE SURFACE BOUNDARIES
WILL WEAKEN THE CAP AND HELP INITIATE HIGH-BASED STORMS LATE THIS
AFTERNOON.  VERY STEEP LAPSE RATES AND A DEEP/DRY SUB CLOUD MIXED
LAYER WILL PROMOTE DAMAGING DOWNDRAFTS...WITH SOME POTENTIAL FOR
UPSCALE GROWTH OF THE STORMS/COLD POOLS INTO ONE OR MORE MCS/S BY
EARLY TONIGHT ACROSS NW KS/NEB.  VERTICAL SHEAR WILL ALSO BE
SUFFICIENT FOR SUPERCELLS CAPABLE OF PRODUCING AT LEAST ISOLATED
LARGE HAIL...NAMELY EARLY IN THE EVOLUTION OF THE STORMS DURING THE
EVENING.

...CENTRAL/ERN DAKOTAS THIS AFTERNOON/EVENING...
A MID LEVEL TROUGH...ENHANCED BY OVERNIGHT CONVECTION...IS MOVING
NEWD FROM NE SD/SE ND TO WRN MN.  CLEARING IN THE WAKE OF THIS
SYSTEM IS ALLOWING SUBSTANTIAL SURFACE HEATING...WHILE BOUNDARY
LAYER DEWPOINTS ARE GENERALLY IN THE LOWER 60S E OF THE SURFACE
BOUNDARY APPROACHING THE CENTRAL DAKOTAS.  HOWEVER...MID LEVEL FLOW
WILL ALSO WEAKEN IN THE WAKE OF THE INITIAL MID LEVEL WAVE...LEAVING
THE STRONGER FLOW/HEIGHT GRADIENTS W OF THE SURFACE BOUNDARY.  THE
NET RESULT WILL BE AN ENVIRONMENT WITH POTENTIALLY MODERATE
INSTABILITY AND VERTICAL SHEAR THAT SHOULD BE MARGINALLY FAVORABLE
FOR SUPERCELLS.  CONVECTION MAY FORM FIRST ALONG THE BOUNDARY FIRST
IN SD...AND THEN SPREAD NNEWD INTO ND BY LATE AFTERNOON INTO EARLY
TONIGHT.  ISOLATED LARGE HAIL AND DAMAGING GUSTS SHOULD BE THE MAIN
SEVERE THREATS.

..THOMPSON/TAYLOR.. 06/15/2006