Mike Leuthold said:

This is a re-post of Mike's comment with the urls activated.

The NAM has had terrible initializations for most of the last week with a semi permanent strong inverted trough in various random parts of northern Mexico. The result of this is that mid level forcast winds have been much stronger (up to 30kts) that what has actually happened, and these winds then caused storms in the model to organize and propagate into the lower elevations, which hasn't happened. The NWS had bit at these poor forecasts more than once with high pops for low elevations and even a mention by SPC sometime last week that the forecast shear was high.This is a link to a model sounding over Mt Lemmon made from the 12z NAM from the previous day (6 Aug).

http://tinyurl.com/n8gkx

This is the actual sounding.

http://tinyurl.com/p2mzx

Perhaps the NWS should put some effort and money into supporting northern Mexico soundings during the summer. The above cases show how poor the models perform when there are no soundings from there. It would be money well spent.
11:59 AM