The latest GFS dynamic tropopause (jet-stream level) forecast below ain't mobile friendly, but it tells it like it is. A ginormous ridge is building over western North America this week, diverting the storm track into northwest Canada and Alaska. Although that ridge eventually weakens and moves downstream, another builds behind it.
Total precipitation produced by the GFS in Utah over the next 10 days is precisely "one Blutarski." In other words, zero-point-zero.
For those of you who don't know what a Blutarski is, watch this clip from Animal House and work harder to expand your educational horizons.
Most medium-range ensemble members are similarly going for dry conditions over the area and nearly the entire mountain west. Perhaps the ridge will be weaker than advertised, shift a bit westward allowing something to spill over the top, or go north enough for the southern branch of the jet to come into our area. That's about all we can hope for.
I'm not one to extrapolate already medium-range forecasts even farther into the future. Much can happen at long lead times. Blocking patterns like this can be very persistent, but I'm inclined not to make forecasts for the 2nd half of December at this time.
For Wasatch Front dwellers, now is the time to reduce driving, carpool, and take transit. The inversion begins to develop today and the cold pool it isolates in the Salt Lake Valley and adjoining lowlands probably won't be going anywhere for a long time unless we can get some sort of dry cold front to slide down the back side of the ridge. That's not impossible, but I wouldn't count on it. Expect today's emissions to be tomorrow's smog.