Most of Utah will be in the southwesterly flow ahead of the mid-latitude trough, resulting in hot, dry, windy conditions Thursday and Friday. It's pretty much a worse-case scenario for fire-weather conditions, so let's be careful out there.
|GFS 700-mb wind vectors and precipitable water (cool and warm colors|
indicate low and high values, respectively)
As can be seen at the end of the loop, this leads to a strong contrast in precipitable water between the two regions. Precipitable water (a.k.a. integrated water vapor) is the depth of water one would have if all the water vapor in the atmosphere rained out. By Saturday morning, values are less than 5 mm over central Utah, but more than 20 mm in portions of southern Arizona.
Thus, the southwest will have it's own "dryline" separating relatively moist and dry air on Saturday.