Weather.com is as good as any - and for road conditions, safetravelusa.com has links to all the states' road conditions websites.
Note that I-80 across Wyoming is notorious for blizzards, whiteouts, black ice, and strong winds. I-70 across Colorado goes through the Rockies at elevations up to 11000 feet, and can also be a problem. You need to make a decision when you reach the I-15/I-70 junction in Utah.
Mequon is no problem, but if you go that way you will have to deal with the Chicago traffic on the way from there to NYC. You are also looking at significant tolls from the WI-IL state line to Youngstown OH (about $36) where you would take I-80 on in to NYC. Best way around Chicago coming from Milwaukee would be I-94 to I-294 to I-80/90, avoid in rush hour.
If you take I-70 across Utah, fill your tank in Richfield or Salina and do the bathroom thing - there are no services whatsoever between Salina and Green River - over 100 miles.