[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 271303
SWODY1
SPC AC 271301

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0801 AM CDT SAT MAY 27 2006

VALID 271300Z - 281200Z

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

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF IL...

...SYNOPSIS...
AMPLIFIED FLOW PATTERN IS FORECAST TO PERSIST TODAY AS DEEPENING
UPPER TROUGH OVER THE PACIFIC COAST STATES MOVES SLOWLY EWD TOWARD
THE INTERMOUNTAIN REGION...AND UPPER RIDGE BUILDS INTO THE ERN
STATES IN THE WAKE OF THE DEPARTING TROUGH ALONG THE ATLANTIC COAST.


AT THE SURFACE...LOW PRESSURE IS EXPECTED TO REMAIN OVER THE
NORTHERN HIGH PLAINS TODAY WITH A QUASISTATIONARY FRONT EXTENDING
NEWD INTO SERN MANITOBA/NWRN ONTARIO...WHILE A COLD FRONT EXTENDING
SWWD INTO WY AND UT MOVES SLOWLY SEWD. A NORTH/SOUTH DRY LINE WILL
CONTINUE OVER THE CENTRAL/SRN HIGH PLAINS.  IN THE EAST...A WEAK
COLD FRONT WILL MOVE SWD ACROSS THE CAROLINAS...THEN RETURN NWWD AS
A WARM FRONT THROUGH THE TN VALLEY TOWARD THE UPPER MS VALLEY.

...NRN PLAINS...
STEEP MID LEVEL LAPSE RATES WILL REMAIN OVER THE REGION TODAY ABOVE
INCREASINGLY MOIST BOUNDARY LAYER ALONG/SOUTH OF THE
FRONT...RESULTING IN VERY UNSTABLE ENVIRONMENT WITH MLCAPE OF
2000-3500 J/KG THIS AFTERNOON AND EVENING.  WARM LAYER ABOVE 850 MB
IN WARM SECTOR SOUNDINGS IS EXPECTED TO INHIBIT CONVECTIVE
DEVELOPMENT INTO THE AFTERNOON...WITH GREATER THREAT FOR CONVECTION
DEVELOPING ALONG/NORTH OF THE FRONT LATER THIS AFTERNOON AND EVENING
IN RESPONSE TO STRENGTHENING CONVERGENCE AND WARM ADVECTION
ASSOCIATED WITH LOW LEVEL JET. ALTHOUGH STRONGEST SWLY FLOW ALOFT
IS FORECAST TO LAG WELL TO THE WEST OF THE WARM SECTOR...VERTICAL
SHEAR NEAR THE FRONT WILL BE SUFFICIENTLY STRONG TO ENHANCE
CONVECTIVE ORGANIZATION AND PROMOTE DEVELOPMENT OF A FEW SUPERCELLS.
 PARTS OF CENTRAL AND ERN ND...ESPECIALLY ALONG/NORTH OF THE
FRONT...APPEAR TO HAVE GREATEST SEVERE POTENTIAL WITH THE
POSSIBILITY OF STORMS PRODUCING VERY LARGE HAIL AND A FEW
TORNADOES...IN ADDITION TO DAMAGING WIND GUSTS.  THIS ACTIVITY IS
EXPECTED TO MOVE NEWD TONIGHT WITH ISOLATED SEVERE STORMS POSSIBLY
CONTINUING INTO THE OVERNIGHT HOURS.

...ERN NEB/IA INTO IL AREA...
RADAR IMAGERY INDICATES TWO MCV'S ASSOCIATED WITH MORNING
CONVECTION...WITH BETTER-DEFINED MCV MOVING EWD INTO ERN IA AND
TRAILING CIRCULATION MOVING FROM ERN NEB INTO EXTREME WRN IA. 
THUNDERSTORMS ALONG LEADING EDGE OF ERN IA MCV HAVE WEAKENED...BUT
ADDITIONAL STORMS HAVE DEVELOPED WWD ACROSS NWRN MO INTO ERN NEB
NORTH OF THE EARLIER OUTFLOW BOUNDARY. 12Z TOP SOUNDING EXHIBITS
STEEP LAPSE RATE ABOVE 680 MB WITH MORE THAN 2000 J/KG OF ELEVATED
CAPE FOR PARCELS ORIGINATING AROUND 750 MB....SUGGESTING A THREAT
FOR HAIL WITH STRONGER CELLS.  ACTIVITY IS LIKELY TO SPREAD EWD
ACROSS EXTREME NRN MO/EXTREME SRN IA INTO MID MORNING BEFORE
WEAKENING AFTER IT MOVES EAST OF THE LOW LEVEL JET.

NEW THUNDERSTORMS ARE EXPECTED TO DEVELOP DOWNSTREAM FROM THE LEAD
MCV THIS AFTERNOON AS IT MOVES SLOWLY EWD TODAY AND INTERACTS WITH
INCREASINGLY MOIST/UNSTABLE ENVIRONMENT OVER PARTS OF NRN/CENTRAL
IL.  COMBINATION OF AMPLE LOW LEVEL MOISTURE /SURFACE DEW POINTS
REACHING 65-70F/ AND STRONG INSOLATION WILL CONTRIBUTE TO
DESTABILIZATION WITH MLCAPE 1500-2500 J/KG.  THUNDERSTORMS ARE
EXPECTED TO INCREASE IN INTENSITY THIS AFTERNOON/EVENING WITH THREAT
FOR LARGE HAIL AND DAMAGING WIND GUSTS.

...TN VALLEY INTO SERN STATES...
MOIST UNSTABLE AIR MASS IS EXPECTED TO CONTINUE ALONG/SOUTH OF THE
FRONT THAT IS FORECAST TO MOVE SWD ACROSS THE CAROLINAS INTO GA. 
STRONG DIURNAL HEATING COUPLED WITH A WEAK CAP WILL RESULT IN
SCATTERED AREAS OF THUNDERSTORMS DEVELOPING THIS AFTERNOON.  WEAK
VERTICAL SHEAR SUGGESTS PULSE STORMS WILL BE THE DOMINANT CONVECTIVE
TYPE WITH POTENTIAL FOR ISOLATED BRIEF WET MICROBURSTS AND HAIL WITH
STRONGER STORMS.

...CENTRAL/SRN HIGH PLAINS...
UNSTABLE AIR MASS IS EXPECTED TO PERSIST ALONG/EAST OF THE DRY LINE
THIS AFTERNOON.  HOWEVER...WEAK LOW LEVEL CONVERGENCE WITHIN A
CAPPED ENVIRONMENT AND MINIMAL FORCING FOR LARGE SCALE ASCENT WILL
LIKELY TO INHIBIT CONVECTIVE DEVELOPMENT.  ALTHOUGH MOST MODELS
EXCEPT PARALLEL NAM GENERATE LITTLE IF ANY CONVECTION IN THE HIGH
PLAINS...FORECAST SOUNDINGS INDICATE CIN WILL GRADUALLY DIMINISH
DURING MAXIMUM HEATING PERIOD WILL WELL-MIXED BOUNDARY LAYER
DEVELOPING.  THIS SUGGESTS THAT A LOW PROBABILITY FOR THUNDERSTORMS
SHOW BE MAINTAINED WITH COINCIDENT THREAT FOR ISOLATED SEVERE CELLS
ALONG/EAST OF DRY LINE.

..WEISS/GUYER.. 05/27/2006