[SWODY1] SWODY1

[Severe Weather Outlook Day 1]

ACUS01 KWNS 230559
SWODY1
SPC AC 230557

DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1257 AM CDT TUE MAY 23 2006

VALID 231200Z - 241200Z

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF CENTRAL/NRN
PLAINS EWD TO SRN MN/CENTRAL IA/NWRN MO...

...SYNOPSIS...
STRONG NEGATIVELY TILTED MID/UPPER LEVEL SHORT WAVE TROUGH WILL
TRACK NEWD ACROSS THE NRN HIGH PLAINS TODAY...THEN TURN EWD ACROSS
SD/NEB TONIGHT.  BAND OF 45-55 KT MID LEVEL FLOW WITHIN THE SRN-ERN
PERIPHERY OF THIS TROUGH WILL SPREAD ACROSS MUCH OF THE CENTRAL/NRN
PLAINS TODAY REACHING THE MID MO RIVER VALLEY TONIGHT. IN THE LOW
LEVELS...A REMNANT SURFACE BOUNDARY/MOISTURE AXIS EXTENDED FROM THE
GULF COAST STATES/LOWER MS VALLEY NWWD ACROSS THE OZARKS TO ERN
KS/NEB TO WRN SD.  NRN EXTENT OF THIS BOUNDARY WILL DEVELOP NEWD AS
A PACIFIC COLD FRONT SPREADS ENEWD ACROSS  SD/NEB/KS.  PRIMARY
SURFACE LOW IS PROGGED TO TRACK NEWD FROM ERN MT INTO SRN CANADA...
WHILE A SECONDARY LOW DEVELOPS OVER CENTRAL/ERN SD AND/OR EXTENDS
INTO ERN NEB BY MID-LATE AFTERNOON.

IN THE WEST...ANOTHER SHORT WAVE TROUGH ROTATING AROUND THE SRN
PERIPHERY OF THE DEEP LOW OVER THE NERN PACIFIC IS EXPECTED TO MOVE
INLAND ACROSS THE PACIFIC NW TODAY.

...PARTS OF CENTRAL/NRN PLAINS TO SRN MN/CENTRAL IA/NWRN MO...
THUNDERSTORMS...SOME POTENTIALLY SEVERE...ARE EXPECTED TO BE ONGOING
AT 12Z THIS MORNING ACROSS WRN PARTS OF THE CENTRAL PLAINS TO SWRN
SD WITHIN DEEP LAYER ASCENT ALONG NOSE OF STRONG NOCTURNAL SLY LLJ
OVER THE WRN PLAINS AND WITH HEIGHT FALLS AHEAD OF APPROACHING
TROUGH.  THIS ACTIVITY IS EXPECTED TO SPREAD NEWD TOWARD THE CENTRAL
DAKOTAS...BUT SHOULD WEAKEN AS THE LLJ DECREASES IN STRENGTH THIS
MORNING.

SLY L0W LEVEL FLOW WILL PERSIST ACROSS THE CENTRAL U.S. WITH LOWER-
MID 60S SURFACE DEWPOINTS RETURNING NWD ACROSS THE ERN PLAINS AND
LOWER MO RIVER VALLEY TO WRN MN.  STEEP LAPSE RATES ATOP THIS
MOISTURE RETURN COUPLED WITH STRONG SURFACE HEATING WILL CONTRIBUTE
TO MODERATE INSTABILITY WITHIN THE WARM SECTOR BY THIS AFTERNOON. 
THUNDERSTORMS ARE EXPECTED TO DEVELOP INITIALLY ACROSS CENTRAL SD IN
THE VICINITY OF THE SURFACE LOW BY MID AFTERNOON... AND THEN SWD
ALONG A DRY LINE INTO CENTRAL NEB....WITH MORE ISOLATED DEVELOPMENT
POSSIBLE SWD INTO CENTRAL KS.  MODERATE INSTABILITY COMBINED WITH
INCREASING SLY LLJ ACROSS THE ERN PLAINS BENEATH STRENGTHENING SWLY
MID LEVEL FLOW WILL RESULT IN FAVORABLE DEEP LAYER AND DIRECTIONAL
SHEAR FOR SUPERCELLS.  LARGE HAIL... SOME POSSIBLY VERY LARGE...AND
DAMAGING WINDS WILL BE LIKELY. IN ADDITION...LOW-LEVEL DIRECTIONAL
SHEAR/CURVED HODOGRAPHS SUGGEST POTENTIAL FOR ISOLATED TORNADOES
WITH INITIAL ACTIVITY AND AS STORMS DEVELOP EWD ACROSS SD/NEB/NRN KS
TOWARD WRN IA.

SLY LLJ IS EXPECTED TO STRENGTHEN THIS EVENING AND VEER OVERNIGHT
FROM THE ERN PLAINS INTO NRN MO TO UPPER MS VALLEY AS 60-90 METER
HEIGHT FALLS DEVELOP EWD ACROSS SD INTO NRN IA/MN WITH THE APPROACH
OF THE UPPER TROUGH.  THIS SUGGESTS UPSCALE GROWTH OF INITIAL
ACTIVITY INTO CLUSTERS OF STORMS...THEN A FORWARD PROPAGATING MCS
MOVING EWD TOWARD SWRN MN/WRN IA THIS EVENING...POTENTIALLY TURNING
SEWD ACROSS IA/NRN MO AND ERN KS TONIGHT.  DAMAGING WINDS SHOULD
BECOME PRIMARY SEVERE THREAT WITH THE MCS...THOUGH HAIL SHOULD
REMAIN A THREAT AS WELL.

...WRN MO/NWRN AR...
ISOLATED STORMS...SOME SEVERE...MAY DEVELOP ALONG THE SURFACE
BOUNDARY EXTENDING SSEWD THROUGH WRN MO INTO NWRN AR AS THE AIR MASS
BECOMES MODERATELY UNSTABLE THIS AFTERNOON.  DEEP LAYER SHEAR WILL
BE SUFFICIENT FOR ORGANIZED STORMS...BUT MODELS SUGGEST SOMEWHAT
WEAK UPPER FORCING WITHIN THE RIDGE AXIS SHOULD LIMIT COVERAGE OF
SEVERE WEATHER.

...ERN MT/WRN ND...
THUNDERSTORMS MAY BE ONGOING AT THE START OF DAY 1 ACROSS THE NRN
HIGH PLAINS.  MODELS SUGGEST THIS ACTIVITY SHOULD PERSIST THROUGH
THE DAY WITHIN DEFORMATION ZONE ALONG NWRN PERIPHERY OF UPPER
TROUGH.  INSTABILITY WILL BE WEAK...BUT DEEP LAYER SHEAR MAY BECOME
SUFFICIENT FOR A FEW SEVERE STORMS MAINLY ACROSS ERN MT INTO WRN ND.

...MUCH OF WA/CENTRAL-ERN ORE/WRN-NRN ID...
ASCENT SPREADING NEWD ACROSS THE PACIFIC NORTHWEST TODAY AHEAD OF
THE APPROACHING PACIFIC SHORT WAVE TROUGH IS EXPECTED TO PROVE
SUFFICIENT IN SUPPORTING THUNDERSTORMS MOVING/DEVELOPING FROM SW-NE
ACROSS THIS REGION TODAY INTO THIS EVENING.  ALTHOUGH INSTABILITY IS
EXPECTED TO BE MARGINAL...SURFACE HEATING COMBINED WITH STEEPENING
LAPSE RATES AND STRONG DEEP LAYER SHEAR SHOULD SUPPORT A FEW SEVERE
STORMS...ESPECIALLY ALONG/E OF THE WA/ORE CASCADES.

..PETERS/GRAMS.. 05/23/2006