Monte I can't offer suggestions, but add (from many trips) the weather looking into the reserve from Walls area can be very daggy and miserable looking over yonder, whilst enjoying reasonable, fine, even nice weather in the Walls.
No theories, but wonder if the Mersey and Cathedral range has some influence.
Sorry, can't be much more help.
Just remember though the ground starts at around 1200 metres and rises from that. And that altitude can usher in anything.
Also come home many times from Walls to Sheffield and the weather has been adverse at home whilst enjoying good weather up there.
This is Tasmania
