Forecasting is hard enough as it is, but it's even harder when you don't know what day it is. The frontal passage in the GFS forecast below is on Tuesday, not Wednesday as indicated in the previous post, which I've now updated. Adjust your sick days accordingly.
And, while I'm at it, I need to highlight the massive difference between the GFS and NAM forecasts. Just check out the striking difference between the latest model forecasts valid 0000 UTC Wednesday (5 PM MST Tuesday). The GFS (top) has a deep upper-level trough and a gangbuster cold front over Utah. The NAM has a much weaker and strung out upper-level trough with the cold front still to our north. For Salt Lake City, the GFS 700-mb (crest level) temperature is -12C, the NAM -2C.
The GFS has repeatedly taken the NAM behind the woodshed this year, with the NAM eventually shifting toward the GFS solution as the forecast lead time decreases. I may get egg on my face for saying this, but I'm leaning strongly toward the GFS solution. I'll add that based on the performance this winter, running the NAM past 48 hours appears to be a complete waste of computer time, at least over the western United States.