Maybe the difference in weather between west and east Sierras is that vast, but I landed in Fresno at about 1pm that day after following the western slopes, and there were zero clouds over the Sierra and zero wind at about 12,000 feet. The weather briefer gave me winds aloft over the Sierra to 20,000ft as L&V. Thats what I saw at that place time at that time.
I don't think there are any liars here, just some interesting weather phenomena and maybe some timing differences (we hit building cumulus at Gorman on the way into WHP taht day at about 3pm)
