Funnily enough chaps, I noticed this myself in exactly the same situation as Skoshi, but wasn't sure if they'd always been like that or whether it was an improvement in one of the earlier patches.
It's definately not new to this patch, and may have been there from the start. Kinda helps explain why clouds are such a performance issue though.
Maybe it shows up most in the cross-country mission because of the strong wind? Maybe.