The last 100% accurate weather forecast
The last totally accurate weather forecast is sometimes said to have been when God told Noah there was a 100% chance of rain.
It all just depends on the weather at that time. Road crews in each state have the responsibility of keeping interstates and other major highways open as much as possible, and they generally clear them quickly after a storm, but you could encounter winter storms along any part of the route that could delay you. Even without major storms, you may encounter ice on the roadway at any point along the I-40 route, and beyond, especially in the early morning. Just keep an eye on the weather as you get close to departure and make your plans accordingly. Keep in mind also that the I-10 route can also have wintry conditions in localized places, so you have to be careful on that route if you choose to go that way.
Outspoken opinions about THD
I am not a fan of the Texas Highway Department in regards to winter weather clean-up expertise Detailed past rants can be found on this forum should you be interested. In any case, if I were you I would certainly use I-40 if only because of the lesser distance to be traveled in Winter across Texas.
Some of the nastiest winter road conditions can be found on I-10 between Van Horn and Ft. Stockton in my opinion. Fort Worth is certainly not immune to ice storms either.
From Rhode Island -- for the shortest and safest route -- personally, I would always counsel I-70 across the Rockies and down I-15 to San Diego. Yep, there are tall mountains in Colorado -- but the Colorado Highway Dept is one of the best in the country. Fastest route would be shortest route!
M.