I am violating one of my cardinal rules today by digging into the small-scale details of a medium-range forecast. Given the large-scale uncertainty that exists at long lead times, this is always a dangerous thing to do, and could set me up for a real egg-on-my-face moment in a few days. However, there's little of interest happening right now, so let's go off into what I call "dream-prog-land."
Hurricane Hilary is presently churning away happily at category 3 in the eastern Pacific, with maximum sustained winds near 115 mph.
The contours in the analysis above are of precipitable water and show that while there is a local maximum near Hilary, the entire eastern Pacific off the coast of southern and central Mexico is quite moist.
The GFS forecast shows that in advance of Hilary, there is a very strong Gulf of California surge that taps into this area of high precipitable water and advects it northward into the lower Colorado River Basin.
The GFS forecast for 1200 UTC 2 October (Sunday morning) includes a tongue of moist air that extends into southwest Arizona with precipitable water values exceeding 35 mm.
Ah, but it's a dry heat! Time will tell if things come together to pull this moisture into Utah. I've already played up the Hilary potential a bit more than I should at such long lead times, but desperate times call for desperate measures.