Express uses Carson Pass - the suggestion for checking with Caltrans is a
good one. In NV the passes range from 6,300 feet to 7,700 feet - it's very
possible you'd run into snow if a storm comes along. East of Cedar City,
UT, the route goes through Cedar Breaks Natl. Monument and that road is
over 10,000 feet, though there is a way around it if the road is closed.
Two passes in CO are over 10,000 feet and 11,000 feet. All of the roads
(Cedar Breaks being the exception) over the passes on the Western
Express are open year round, but storms could close them at any time
until the plows have cleared the snow.