[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 281304
SWODY1
SPC AC 281302

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0802 AM CDT SUN MAY 28 2006

VALID 281300Z - 291200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER THE NRN PLAINS...

...THERE IS A SLGT RISK OF SVR TSTMS OVER THE SRN HIGH PLAINS...

...SYNOPSIS...
WATER VAPOR IMAGERY SUGGESTS JET STREAK IS MOVING INTO BASE OF THE
DEEP UPPER TROUGH OVER THE WRN STATES...SUGGESTING SYSTEM HAS
REACHED MAXIMUM AMPLITUDE.  AS JET STREAK BEGINS TO MOVE NEWD ON
EAST SIDE OF TROUGH...TROUGH WILL ALSO LIFT NEWD ACROSS NRN ROCKIES
TODAY AND INTO CANADA TONIGHT AS DOWNSTREAM RIDGE BUILDS OVER ERN
STATES.

AT THE SURFACE...NORTHEAST/SOUTHWEST QUASI-STATIONARY FRONT FROM
SERN MANITOBA INTO LOW OVER EXTREME NRN SD...THEN CONTINUES SWWD
INTO SECOND LOW OVER NERN CO.  A COLD FRONT TRAILS SWWD FROM THE CO
LOW INTO FOUR-CORNERS REGION AND NWRN AZ.  THE SD LOW IS EXPECTED TO
LIFT NEWD ALONG THE FRONT TOWARD NERN ND THIS AFTERNOON AND INTO
SERN MANITOBA TONIGHT. THE CO LOW IS FORECAST TO MOVE LITTLE TODAY
BEFORE LIFTING NEWD AND WEAKENING TONIGHT AS COLD FRONT BEGINS TO
MOVE EWD ACROSS THE NRN AND CENTRAL PLAINS...REACHING A NRN MN/ERN
NEB/SERN CO LINE BY 29/12Z.  A NORTH/SOUTH DRY LINE EXTENDING FROM
WRN NEB AND KS INTO SERN NM AND THE TRANSPECOS REGION OF TX IS
EXPECTED TO MIX EWD THIS AFTERNOON.

IN THE EAST...WEAK COLD FRONT EXTENDS FROM THE GA COAST NWWD INTO
NRN AL...CONTINUING NWWD AS A QUASI-STATIONARY FRONT ACROSS
IND...THEN AS A WARM FRONT INTO NRN MN. SERN PART OF THE FRONT WILL
MOVE SWD INTO THE FL PENINSULA TODAY.

...NRN PLAINS/NRN MN...
ELEVATED THUNDERSTORMS HAVE DEVELOPED OVER EXTREME NRN MN NORTH OF
THE SURFACE WARM FRONT WITHIN THAT LAST HOUR.  12Z INL SOUNDING
EXHIBITS STRONG INSTABILITY ABOVE COOL SURFACE-BASED LAYER...WITH
MODEST EFFECTIVE SHEAR.  PRIMARY THREAT WILL BE LARGE HAIL OVER
PARTS OF KOOCHICHING...NRN ST LOUIS...AND POSSIBLY LAKE AND COOK
COUNTIES DURING THE NEXT 2 HOURS...AFTER WHICH ACTIVITY SHOULD MOVE
INTO ONTARIO.

AMPLE LOW LEVEL MOISTURE /SURFACE DEW POINTS IN THE MID/UPPER 60S/IN
THE WARM SECTOR COUPLED WITH STEEP MID LEVEL LAPSE RATES ASSOCIATED
WITH ELEVATED MIXED LAYER WILL CONTRIBUTE TO STRONG INSTABILITY THIS
AFTERNOON WITH MLCAPE REACHING 2500-3500 J/KG. 12Z SOUNDINGS SHOW A
STRONG CAP JUST ABOVE 850 MB...AND THIS IS LIKELY TO REMAIN IN PLACE
INTO THE AFTERNOON INHIBITING DEVELOPMENT OF SURFACE-BASED
CONVECTION EAST OF THE FRONT.  MODEL GUIDANCE INDICATES INITIAL
STORMS THIS AFTERNOON WILL BE ELEVATED WEST OF SURFACE FRONT OVER
NORTH CENTRAL CO/ERN WY/NEB PANHANDLE AND WRN SD...FORMING IN
RESPONSE TO DYNAMIC FORCING ASSOCIATED WITH MID/UPPER LEVEL JET
STREAK LIFTING NNEWD FROM THE CENTRAL TOWARD THE NRN HIGH PLAINS. 
THIS CONVECTION IS LIKELY TO SPREAD NEWD WEST OF THE FRONT INTO
PARTS OF THE DAKOTAS DURING THE EVENING...WHILE POTENTIAL EXISTS FOR
ADDITIONAL STORMS TO DEVELOP ALONG THE FRONT FROM ERN SD INTO
EXTREME ERN ND/NWRN MN.  STRONGEST DEEP LAYER SHEAR WILL BE LOCATED
WEST OF THE FRONT AND WILL SUPPORT ELEVATED SUPERCELLS IN THAT
REGION.  ALTHOUGH SHEAR DIMINISHES WITH EWD EXTENT INTO THE WARM
SECTOR IT SHOULD BE SUFFICIENT TO ENHANCE ORGANIZED SEVERE STORM
THREAT WITH ANY SURFACE-BASED STORMS ALONG THE FRONT.  LARGE HAIL IS
EXPECTED TO BE THE PRIMARY THREAT ALONG WITH DAMAGING WIND GUSTS. 
ACTIVITY IS EXPECTED TO CONTINUE NEWD INTO THE OVERNIGHT HOURS.

...CENTRAL/SRN HIGH PLAINS...
UNSTABLE AIR MASS WILL EXTEND ALG/EAST OF THE DRY LINE AS MOISTURE
RETURNS WWD IN THE WAKE OF MORNING CONVECTION OVER PARTS OF SRN OK
AND CENTRAL TX.  ALTHOUGH LARGE SCALE ASCENT WILL BE MINIMAL AS
UPPER TROUGH LIFTS NEWD AWAY FROM THE REGION...COMBINATION OF STRONG
HEATING AND WEAK CONVERGENCE ALONG THE DRYLINE MAY BE SUFFICIENT TO
WEAKEN CAP AND PERMIT DEVELOPMENT OF A FEW THUNDERSTORMS DURING THE
LATE AFTERNOON AND EVENING.  VERY STEEP LAPSE RATES WILL ENHANCE
UPWARD ACCELERATION FOR ANY PARCELS THAT REACH THE LFC...AND DEEP
WELL-MIXED BOUNDARY LAYER WILL SUPPORT STRONG DOWNDRAFTS SUGGESTING
THREAT FOR LARGE HAIL AND STRONG WIND GUSTS. SREF ETA-KF MEMBERS AND
06Z ETA SUGGEST MOST LIKELY REGION FOR CONVECTIVE DEVELOPMENT WILL
BE ALONG GAG-SJT AXIS...AND SLIGHT RISK HAS BEEN ADDED TO THAT
REGION.

...CENTRAL/ERN TX AND SERN OK INTO SWRN AR AND LA...
ANIMATED RADAR IMAGERY OF CONVECTIVE SYSTEMS DURING THE PRE-DAWN
HOURS INDICATED THE PRESENCE OF MCV/S OVER CENTRAL TX AND EXTREME
NRN TX NEAR THE RED RIVER EAST OF SPS. IF THESE SYSTEMS MAINTAIN
ORGANIZATION AND CONTINUE EWD TODAY...THEY MAY INCREASE THUNDERSTORM
DEVELOPMENT FROM CENTRAL/ERN TX AND SERN OK EWD INTO SWRN AR AND LA.
 PRESENCE OF MODERATELY UNSTABLE PRE-CONVECTIVE ENVIRONMENT WITH
MLCAPE OF 2000-3000 J/KG AND DYNAMICALLY ENHANCED MID LEVEL
WINDS/ASSOCIATED VERTICAL SHEAR SUGGESTS POTENTIAL FOR ISOLATED
SEVERE STORMS THIS AFTERNOON AND EVENING.

...PARTS OF AL/GA/FL...
COLD FRONT SAGGING SWD/SWWD ACROSS PARTS OF GA INTO AL AND FL IS
EXPECTED TO PROVIDE FOCUS FOR THUNDERSTORM DEVELOPMENT TODAY.  12Z 
REGIONAL SOUNDINGS SUGGEST MLCAPE WILL INCREASE TO 2000-2500 J/KG AS
STRONG INSOLATION OCCURS.  WEAK VERTICAL SHEAR COUPLED WITH DRY AIR
AVAILABILITY AND STEEP LOW LEVEL LAPSE RATES SUGGEST POTENTIAL FOR
PULSE STORMS WITH MARGINAL HAIL AND ISOLATED WET MICROBURSTS.

..WEISS/GUYER.. 05/28/2006