AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TULSA OK
1049 PM CST MON JAN 7 2008
MESOSCALE UPDATE…
SURFACE TEMPERATURES HAVE REMAINED STEADY OR HAVE RISEN A COUPLE OF DEGREES IN THE LAST HOUR…SO THE ATMOSPHERE HAS DESTABILIZED FURTHER SOUTH OF THE BAND OF SUPERCELLS THAT EXTENDS ACROSS NORTHEAST OKLAHOMA AND THE NORTHWEST TIP OF ARKANSAS. THE LIFTED INDEX HAS LOWERED TO -3 WITH SURFACE BASED CAPE STILL BETWEEN 1000 AND 1500 J/KG.
DEEP-LAYER AND LOW-LEVEL SHEAR VALUES REMAIN HIGH ALONG AND SOUTH OF THE SUPERCELLS WITH STORM-RELATIVE HELICITY BETWEEN 200 AND 375 M2/S2. THEREFORE SUPERCELL STORM STRUCTURES WILL CONTINUE WITHIN THE BAND.
ELEVATED CONVECTION IS DEVELOPING IN EAST-CENTRAL OKLAHOMA AND WESTERN ARKANSAS AND IT IS EXPECTED TO CONTINUE TO INCREASE AS THE MAIN UPPER SYSTEM APPROACHES. ANY OF THESE CELLS HAVE THE POTENTIAL TO ROOT IN THE BOUNDARY LAYER. IF A CELL DOES BECOME ESTABLISHED IT WOULD RAPIDLY BECOME A SUPERCELL. ALL INTERESTS IN THESE AREAS SHOULD CLOSELY MONITOR RADAR TRENDS FOR SUDDEN STORM ORGANIZATION.
AT 10PM…ANALYSIS GRIDS SHOW THAT STORM MOTIONS ARE MORE ALIGNED WITH MID-LEVEL FLOW AND STORM-RELATIVE WINDS AREA DECREASING. THE RESULT IS EXPECTED TO A DROP IN THE TORNADO POTENTIAL WITH THE EXISTING CELLS…BUT THE THREAT IS NOT TOTALLY GONE. FURTHER THE SHEAR IN THE LOWEST KM OF THE ATMOSPHERE IS HIGH AND TRANSITORY BUT STRONG LOW-LEVEL
ROTATIONS COULD OCCUR WITH ANY STORM. THE ARKANSAS RIVER VALLEY WILL NEED TO BE MONITORED CLOSELY FOR THESE TYPES OF CIRCULATIONS.
THE SURFACE LOW IS DEVELOPING INTO OSAGE COUNTY AT THIS TIME AND THE COLD FRONT WILL BEGIN TO ACCELERATE SOUTHEAST. THUNDERSTORMS…SOME SEVERE WILL OCCUR WITH THE COLD FRONT AS IT SWEEPS OVER THE REGION DURING THE OVERNIGHT HOURS.