Let's begin by taking a look at our downscaled NAEFS product for Alta Collins, focusing on the period through 0000 UTC 10 February (5 PM MST Thursday). Water equivalent totals vary from about 3 inches to nearly 9 inches, the latter a truly astounding amount. Note that most of the higher amounts (and nearly all of the members that are above the mean, are produced by the Canadian model. You have to love our friends in the Great White North!
Another contributor to the spread is the sensitivity of the forecast to cyclogenesis (cyclone development) over the eastern Pacific. This cyclogenesis in turn affects the strength of the developing ridge over the western US (note how the ridge over the western US amplifies in the loop below) and the track of moisture and storminess into Utah.
|GFS forecast valid 1200 UTC 6 Feb – 0000 UTC 9 Feb 2017|
|Source: Atmospheric River Portal, http://mead.ucsd.edu/|
Had enough yet? Let's talk about wind. Yup, it's nuking the entire period. Lots of wind barbs in the NAM time-height section. Hold on to your hats!