Thursday, November 11, 2010

A Narrow Opportunity for Severe Weather Tomorrow

Severe storms are possible tomorrow across northern Texas and central Oklahoma ahead of a very strong 500mb vort max moves across the Texas Panhandle into western Oklahoma Friday evening. Even though low level instability will be much lower than usual for severe thunderstorm development, the dynamics of this system appear to be enough to overcome this limitation. All the following forecast information is based off the 11/11/10 12Z NAM.
Right now SBCAPE is forecast to be between 500 and 700 J/kg for a narrow window of time Friday afternoon, with nearly 100 J/kg in the lowest 3KM of the atmosphere. If any additional daytime heating can occur, SBCAPE could reach 1000 J/kg in a few areas.

In addition to the available instability, 0-6km shear will me more than ample for supercell development. Shear values will be close to 50 knots over the greatest axis of instability which could promote robust rotating updrafts. Also, the shear vectors will remain perpendicular across the boundary of storm development so look for to develop in a non-linear form making supercells a likely storm mode

As for the tornado threat, 0-1km SRH is over 200 for a few hours ahead of the cold front so any storm that can develop in this environment could produce enough low level rotation. This along with 0-1km shear values over 20 knots should be enough to allow an isolated tornado or two to develop if storms can initiate ahead of the cold front.

Right now the SPC has a 5% chance of severe weather in this area with a mention of a supercell or two. I do believe that if the forecast trend the NAM is indicating continues a slight risk will be issued, maybe as early as the next day 2 outlook.

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