Wednesday, March 14, 2012

Going into Outlier Mode

The atmosphere will be going into outlier mode starting this weekend, although it remains unclear how much that will help the Wasatch snowpack.

As shown in the 84-hour GFS forecast below, a deep upper-level trough is forecast to dig into the American Southwest this weekend.  This leads to the development of an Intermountain cyclone over Nevada and Utah on Saturday.

As presently forecast, Saturday afternoon could be quite windy and dusty over much of western Utah.  The GFS forecasts 50 knot (25 m/s) southerly winds at 700 mb (roughly 10,000 ft), which is about as high as they get around here.  There is also a strong pressure gradient draped over the southern half of the state.  Whether Salt Lake and the Wasatch Mountains get the big blow will depend on the position of the surface trough, although right now, the models are placing it near the Utah–Idaho border, which means we should see strong the strong southerlies.  Dust is likely, although how inundated we get will depend on trajectories originating from dust-source regions in southwest Utah.

Right now, the GFS brings the cold-air into northern Utah Saturday night and Sunday, along with a band of frontal precipitation.

This is yet another digging, splitting system, so snowfall amounts in the Wasatch Mountains are going to depend quite a bit on the details of the trough position, track, and intensity, as well as whether or not things get going in the post-trough environment early next week.  Colder air is coming, but for the precipitation forecast, the devil is in details that are difficult to predict with confidence at these long lead times.  Keep your fingers crossed.    


  1. You seem really hesitant to make a prediction on this one. You've been doing this a long time though, what's your gut telling you?

    1. It's telling me I've done this long enough to know I'm not sure I can confidently predict what is going to happen at this long lead time. Sometimes experience clues you in on the broad range of possibilities, rather than a specific forecast. This is a situation where specific predictions for specific locations are difficult.

  2. Confidence in big snow for Wasatch is increasing according to Bastardi

  3. Just wanted to say thanks, at least for me it's your commitment to reason and logic in the face of forecast hype that makes this blog one of my favorite weather resources.