Intended to be an open discussion (I don’t know everything) …
We are fortunate to have many forecasting tools for Marshall. One of my favorites is the windgram-style graphs: Soaring Predictor and FlyMarshall.
But what to think when there are conflicting predictions of max soaring altitude (PG symbols)? Today we have (graphs in attachment):
7k at 2pm, from Soaring Predictor.
Shy of 4k at 3pm, from FlyMarshall.
One can use a live camera (noon snapshot in attachment) to qualify the inversion layer, and for today (image attached) we have a summer classic low/dense/defined smog layer. One can hope that the air mass containing this visible low inversion is far enough away (other side of valley) from launch to still allow passage of thermals near Marshall. The odds of unimpeded thermals are best when the wind was blowing North just before our flight, as when the day progresses the onshore flow will move that inverted air mass towards launch and increase the odds of the thermals getting blocked low.
The best way to know for sure is to get out there, fly and make other jealous by reporting back.