Seeing Question

I live in the pollution capital of the United States, otherwise known as Fresno, CA. I have noticed a strange type of condition that maybe someone can explain. In early evening a few minutes before sunset the planets are just as crisp and clear as ever. This condition only lasts for a few minutes until the sun has set and a little beyond. I can then watch "in the eyepiece" and begin to see a very fast moving air current that continues the remainder of the night. It looks like a jet stream and blurs the planets and destroys resolution. Upon checking, the jetstream is nowhere near my location "its over 1000 miles away". Solar views during the day are near perfect. My visual seeing is < mag 4 at anytime due to light and smog. I live 4 miles west of the the metropolis in a huge, hot "over 100 degrees" valley. What do you think this fast moving air may be ? And my surface air is dead calm !!

Possibly has something to do with all the heat that concrete retains being given up.

You should regularly have really good seeing in Fresno, maybe you are just in a bad spot, try moving around a bit. I know that here in San Diego on the same night one spot (no concrete or buildings around) will be horrendous and a spot just a mile away will be a Pickering 8 or better on a typical night, thats if that damned marine layer would just go away!

Steve,

I believe you may have the answer with the "low level" jet. It sure fits the description to a tee. For the last two summers I have struggled through this, now I know. Its the pits and seems to cover the whole valley "over 300 miles long and 140 miles wide" when it begins. No way to out-run it so, I will have to take my scope or scopes up above 4,000 ft. Thanks so much for finding that info !! I even feel better just because I know what it is now. I just cannot wait to move back to Arizona, my home state.