Because I need to travel to get dark skies, I'm curious how much of a certainty a good weather report is of good seeing?
Given no moon, low humidity, low wind no Jetstream, and no cloud, how likely are good conditions? Is it a dead cert, or merely much more likely compared to unfavorable conditions?
It's never certain. Humidity plays a role as well. If all else looks good, high humidity tends to favour seeing, while low humidity tends to go with better transparency. Rarely you get both excellent seeing and excellent transparency. To catch nights like that you just have to go out and try your luck often enough and eventually you'll get one and it will have been worth it.
