June 12 TWISTEX Update

Status: Awaiting Next Deployment
Location: Terril, IA


Severe weather across the plains is in the forecast for today as well as tomorrow, with some enhanced risks possible. Downside to this is the lack of good surface parameters, creating the threat of mainly large hail and damaging winds as the storms get into multicluster lines and even squalls. This occurred last night with the system and is expected to occur today/tonight as well across areas of the Dakotas, Nebraska southward through Kansas. Wednesdays' threat is also there over portions of the plains states, best threat currently over areas of KS/OK and possibly TX. However even in this area the shear with the system is lacking and thus a supercell threat is marginal. Other thunderstorms are possible throughout the plains tomorrow, severe threat is less due to the lack of shear and instability over the area. The marginal threat of tornadoes and really overall severe threat means TWISTEX is not expected to be operational today/tomorrow.

Thursday the system continues to stall over the plains states, with the best severe threat currently confined to areas of the northern plains (ND/SD/MN) and the southern plains (TX/OK). The southern plains is still lacking sufficient shear for a good supercell threat, however multicell lines are the focus for severe weather there once again. The northern plains threat however does have good support thanks to the trough moving into the area. This is allowing a more widespread event to take place, with shear values that do look sufficient enough for a supercell threat. The tornado threat on Thursday is still minimal however, thus TWISTEX operations will once again not be likely. Once again over much of the plains a linear thunderstorm event may take place, from the Canada border into KS and other lines in the southern plains as well with their multicell severe threat.

In the extended outlook, the next trough that comes onto the plains looks to come by this weekend. The SPC has outlined areas of the northern plains on Sunday. Continued threat on Monday over areas of the plains as well according to the SPC. Models are still grasping solutions on how this one will play out, Saturday evening still has zonal flow over the northern plains, but is still increasing the speeds at the upper levels. By Sunday the trough has dug in and the wind speeds at 500 are much better, being southwest between 40-60 kts over the Dakotas/Minnesota. Monday is a little less exciting on last nights' GFS model run, the trough expands out and the sharpness of the trough is weakened. Still good west/southwest winds are in place over areas of NE/IA into the Great Lakes area and thus a severe threat is not out of the question. The rest of the month is up in the air, with model runs consistently featuring some type of ridge or blocking pattern over the plains. This doesn't bode well for TWISTEX operations, but any small disturbance could occur and provide some severe threat. Continued daily updates until TWISTEX operations resume...