Most of the precipitation for the central Wasatch looks to be primarily frontally forced. The large scale setup is shown below and features an upper level trough that is initially tilted from southwest to northeast (referred to as "positively" tilted by meteorologists) that closes off and becomes more north-south oriented as it moves inland across the western US.
This has both pluses and minuses for snowfall prospects in the central Wasatch. The plus is that the front may slow as it drags through northern Utah, extending the period of frontal snowfall, as depicted below in the 1200 UTC NAM forecast. At 000 UTC 20 January (5 PM MST Friday), the surface front is over Utah County with precipitation over the northern Wasatch.
Frontal precipitation fills in, however, as the front phases with moisture sneaking around the southern end of the Sierra Nevada over the next 3 hours.
That precipitation continues for another 3 hours as the front makes slow progress into southern and eastern Utah.
By 0900 UTC 20 March (2 AM MST Saturday) the main frontal band is just downstream of the central Wasatch, with some post-frontal snow showers persisting.
The minus for snowfall prospects is with the low closing off, the post-frontal winds shift very quickly to northerly, when we would prefer a period of northwesterly flow for better orographic forcing. Note in the Salt Lake City time height section below that the post frontal flow is predominantly northerly and deepens gradually from about 0Z Saturday through 6Z Sunday.
Actual numbers derived from the 12Z NAM show the wet bulb zero dropping during the day Friday (snow level is usually about 1000 ft below this level), with values low enough that most of the precipitation produced during this event should fall as snow in the mountain valleys. Perhaps Mountain Dell might see a bit of rain to start, but then turn over to snow. Total water equivalent at Alta is 0.64" through Saturday at 8 AM, with snow densities decreasing during the storm for a right-side up snowfall.
Looking more broadly at the ensembles shows that the NAM is roughly in the upper half of the SREF plume for Alta. Through 18Z 20 January (11 AM) the SREF members put out anywhere from 0.3 to 0.8 inches of water, the former being a slightly better than dust on crust event adding up to perhaps 4 inches of snow, the latter representing a lower end deep powder day with perhaps 10-12 inches of snow.
That spread represents variations in the strength and speed of the front. Increases in precipitation after 18Z 20 January occur in some model runs that are more bullish on the post-frontal precipitation.
I continue to keep expectations low and hope for the best.