Severe Weather Discussion for January 7, 2008.
– Isolated severe thunderstorms are expected from eastern Texas/western Louisiana northward to southeast KS/southwest MO, thisi includes all of Arkansas and eastern 1/3rd of Oklahoma. Primary threats are large hail and strong winds, isolated tornadoes are possible with discrete storms.
No change to prior forecast reasoning. 12z models remain consistent, although the 12z GFS has appeared to slow the upper system some. This is not a shocker given the strong wind fields aloft. The models have also played a lot with the surface features, positioning the dryline all over eastern Oklahoma. Climatology favors an eastern Oklahoma event into Arkansas as moisture will have a tough time returning into central or western Oklahoma. Additionally, 850mb flow appears to be veered preventing much westward movement.
SPC Day 2 is responsible, but probably too far east. I prefer including a little more Oklahoma at this point. Either way, instability values look marginal given low sun angle and resultant surface heating. Believe that 750-1000 J/Kg is reasonable and will probably occur across parts of eastern Oklahoma into Arkansas. Storms should initiate during the afternoon hours as height falls and strong 500mb jet moves across the threat area. GFS shows two vortmaxes with the first one moving through midday and the second one late afternoon. The models have also caught onto the surface low reforming into SW OK as the main system lifts into the state. There is little to no vorticity advection in the threat area, so lift will be generated by mid-level flow and some surface convergence. Event is more of the medium slight-risk level ATTM, although I will continue discussions.
Farther west showers should develop along the cold front as it moves into Oklahoma. Snow is expected in northern Oklahoma, however little accumulation is expected.
Risk area for any part of OK/TX (valid: 01/07, Day 1):
Level 1 – Normal
For more information, weather news, weather blog, and chase summaries go to http://www.hook-echo.com.