There are several main players driving the US weather today and through the week:
1) Deep trough of low pressure carving its way through the western US with very cold air behind the cold front. The jet stream and associated cold front is now all the way to southern California and Arizona.
2) The strongest portion of the jet stream with this outbreak resides over the northern Plains. Strong dynamics within the jet is leading to moderate to heavy snowfall. Looping the image nicely shows the jet stream powering through the Plains.
3) High pressure will build into the southeastern US the next several days, providing warm conditions with highs reaching into the upper 60s to mid 70s. The far southeast will be where the cold blast stalls this weekend.
Its not difficult to tell where the cold air is powering through. Here is the latest 24 hour temperature changes when compared to Tuesday morning.