[SWODY2] SWODY2

[Severe Weather Outlook - Day 2]

ACUS02 KWNS 200554
SWODY2
SPC AC 200554

DAY 2 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
1154 PM CST TUE DEC 19 2006

VALID 211200Z - 221200Z

...NO SVR TSTM AREAS FORECAST...

...SYNOPSIS...
STRONG MID/UPPER LEVEL CYCLONE -- NOW EVIDENT IN MOISTURE CHANNEL
IMAGERY OVER SRN AZ/WRN NM -- IS FCST TO LIFT NEWD ACROSS SRN HIGH
PLAINS AND PIVOT OVER KS THROUGH PERIOD.  MOST SREF MEMBERS AND
OPERATIONAL MODELS INDICATE CYCLONE TRACK SOMEWHAT S OF PREVIOUS
PROGS ACROSS KS...BEFORE DEEP-LAYER CYCLONE BECOMES MORE VERTICALLY
STACKED AROUND 22/12Z.  MOST PROGS DO DIFFER IN SPEED OF SYSTEM
ALONG ESSENTIALLY SAME TRACK AFTER 22/00Z...WITH OPERATIONAL
SPECTRAL AND SREF/RSM MEMBERS PLACING LOW IN IA...MOST ETA/ETA-KF
MEMBERS OVER NE/MO BORDER REGION...AND WRF BACK IN NERN KS.  THIS
MAY BE RELATED TO HOW THESE MODELS HANDLE CYCLOIDAL MOTION OF
MIDLEVEL VORTEX S OF UPPER LOW...AS ASSOCIATED VORTICITY MAXIMA
PIVOT AROUND SRN/ERN SEMICIRCLES OF BROADER CIRCULATION.  CONSENSUS
FAVORS ETA/ETA-KF TRACK.

THESE SPEED/TIMING DIFFERENCES TRANSLATE TO SFC...WHERE SPECTRAL
RUNS FCST COLD FRONT ACROSS NWRN MS AND LA...WELL AHEAD OF MOST
OTHERS.  GIVEN LACK OF SUBSTANTIAL MID-UPPER SUPPORT FOR ERN SURGE
OF LOW LEVEL FRONT...WILL TREND FCST TOWARD SLOWER WRF/ETA BASED
FCST AT SFC.

...W GULF COASTAL PLAIN...MS DELTA REGION...
CONDITIONAL SVR PROBABILITY EXISTS -- MAINLY IN FORM OF AT LEAST
MRGL TORNADO THREAT AND PERHAPS DAMAGING WIND.  ONCE MESOSCALE
UNCERTAINTIES ARE BETTER RESOLVED...UNCONDITIONAL PROBABILITIES MAY
BE RAISED ENOUGH TO WARRANT CATEGORICAL OUTLOOK. 

AHEAD OF SFC COLD FRONT...EXPECT DEEPLY MOIST PROFILES AND
ASSOCIATED WEAK LAPSE RATES...BUT FAVORABLE KINEMATIC PROFILES.  IF
SUSTAINED/SFC-BASED TSTMS CAN FORM...VERTICAL SHEAR WILL BE
FAVORABLE FOR SUPERCELLS AND SMALL BOWS.  FCST SOUNDINGS SUGGEST
CONSIDERABLE VEERING WITH HEIGHT AND AROUND 40-50 KT SHEAR IN 0-6 KM
LAYER.  CURRENT SFC ANALYSIS...FCST TRAJECTORIES AND MODIFIED WRF
SOUNDINGS INDICATE MID 60S TO NEAR 70 F SFC DEW POINTS WILL
PENETRATE INLAND EXTREME SE TX AND SRN LA...PERHAPS AS FAR N AS I-20
BY END OF PERIOD.  BOUNDARY LAYER FORCING INVOF FRONT IS FCST TO
DIMINISH WITH TIME AS STRONGEST PRESSURE FALLS MOVE AWAY FROM
AREA...HOWEVER SBCINH SHOULD BE WEAK IN MARINE AIR MASS.  THIS WILL
LEAVE DEVELOPMENT STRONGLY DEPENDENT ON MESOSCALE FOCI SUCH AS
OUTFLOWS...FRONTAL/PREFRONTAL CONFLUENCE LINES AND/OR
DIURNAL/DIFFERENTIAL HEATING BOUNDARIES.  BREAKS IN PRECIP/CLOUD
COVER AND ASSOCIATED INSOLATION MAY ENHANCE BUOYANCY DURING DAYLIGHT
HOURS...OTHERWISE MLCAPES SHOULD REMAIN GENERALLY AOB 500 J/KG.

..EDWARDS.. 12/20/2006