I just completed a marathon trip to Park City, UT and back to North Carolina. I want to post some information which may be of assistance to those planning cross-country trips in winter.
Here in the RTA Forums we frequently hear from those looking for "southern route" snow-free crossings. These are of course not to be found and we must repeatedly tell folks just that. What I am here to comment on really relates to travel in the northern half of the Rockies as it relates to route-planning.
I have regularly commented on the I-90 corridor in Montana and its relative lack of high passes and high elevations in general, and have noted the high ground between Cheyenne and Laramie, WY along I-80 as an example of a problem area which can be avoided if I-90 more or less serves the trip planner just as well. Some more map study and my annual ski trip brings this all the more into focus.
The bottom line is practically all of I-80 in WY can be a bitter pill. Excepting the 30 miles between Cheyenne and the Nebraska border, the entire I-80 corridor is above 6,000' in elevation. "The Summit" between Cheyenne and Laramie is 8,640'. Within 10 miles west of Cheyenne I-80 reaches 7,000' remains at or above that elevation until reaching a point just east of Rawlins, for a distance of over 110 miles. Most of I-80 between Rawlins and Evanston, at the UT border, holds elevations just under 7,000'.
With elevation comes wind and snow. While it's clear the WY cavalry manning the plows are among the best, with so much high-elevation roadway to cover, the wind becomes a fierce enemy and keeping the road clear can become impossible, with temporary closures becoming necessary. The most frequently-closed segment is over "The Summit" between Cheyenne and Laramie, and the WY DOT closes the entire section since there are essentially no traveler services (motels, restaurants, etc) over the 50 mile segment.
We were prevented from even attempting to cross WY as we reached it on New Year's Eve by closure between Cheyenne and Laramie in the late afternoon. We overnighted in Cheyenne and embarked at 6:30am on New Year's Day at 7 degrees above zero and 15-25 mph winds. Within a very few miles, we'd gotten into winds of 35 mph and above and blowing snow. Visibility was very poor. The Summit was funneling winds of at least 50 mph and the temperature was 10 below zero at 7:30am. Laramie was OK but the hills between Laramie and Rawlins were terrible: more winds in the 35-45mph range blowing snow, and whiteout conditions. The Wyoming DOT has adjustable speed limit signs on it and had mandated a 35 mph top speed. The WY State Troopers were actually out giving tickets for exceeding the posted limits! We had to follow the big rigs to within 15-20 yards to avoid losing sight of them. At a point around 20 miles east of Rawlins, we'd dropped down enough that the visibility was good and the speed limits were the normal 75 mph. From Rawlins to Rock Springs, however, we had cross winds in the 25-35 mph range which blew snow across the road, obscuring the many icy spots, and we never saw temps above 10 above zero.
The point of all of this is that I-80 across WY can be a serious challenge and planning extra time to deal with closures is highly recommended. Taking I-80 instead of much lower I-90 simply because I-80 is further south is a fool's errand--the elevation difference averages 2,500-3,000', and Montana's highest point along I-90 is Homestake Pass at 6,700'. Where the overall distance between origination and destination are similar, taking I-90 across Montana into ID and WA can be a materially gentler winter trip than a more direct route through WY on I-80. Montana's I-90 has the cities of Billings, Bozeman, Butte, and Missoula, plus a number of small towns, along I-90, while distances between cities and services in Wyoming are much greater.
So, go for it, RoadTrippers. Just keep an eye peeled at weather systems present in and headed for Wyoming and keep the Wyoming 511 info handy on the cellphone, smartphone, or laptop in order to avoid surprises, and keep plenty of de-icer in the windshield fluid reservoir.