State DOTs have good web sites with road conditions and web cams
WSDOT.gov
tripcheck (Oregon)
Idaho
Most have some sort of 511 service
NOAA, National Weather service has maps with warnings. I also like to use their 7day forecast tailored to a specific location (adjusted for altitude, etc).
I90 pass is listed as wet and bare; forecast is snow/rain, i.e. borderline temperatures. I'd go for it, especially if driving in daylight.
Oregon I84 as no weather warnings.
Idaho is showing 'good' for roads in the Snake River plain.
http://www.wrh.noaa.gov/pih/It looks like your chances of snow increase as you get closer to Utah.
