Ignore the weird men in top hats and the furry creature they pull out of the ground. A storm is on tap and whether or not winter has six weeks left is irrelevant to your ski plans for this week.
The storm is somewhere between quick hitter and classic frontal passage. It's a bit larger than the former, but not built quite as well as the latter. If it holds together, it will give us a deep powder day. If it doesn't, then it will be something and this year we can't complain.
Evidence that something is coming is provided in the orographic cloud parked over Lone Peak and the Alpine Ridge south of Little Cottonwood this morning.
That cloud won't produce much today and may even dissipate for a bit, but it is a reflection of strengthening southwesterly flow in advance of an approaching cold front.
I'll use the more pessimistic NAM to describe the event so as not to get hopes too high. As the cold front approaches northern Utah, moist-southwesterly flow leads to the development of snow showers late tonight and tomorrow morning over the Wasatch Range.
Snowfall intensifies over the mountains and develops over the Wasatch Front with the approach and passage of the cold front. Snow levels should drop to the valley floor with frontal passage.
This is followed by the post-frontal crapshoot where much depends on flow direction and moisture availability.
The time-height section for the airport (remember, time increases to the left) shows the surface frontal passage tomorrow morning at around or just after 1500 UTC (0800 AM MST).
Ahead of the front is the moist, southwesterly flow, although the moisture is fairly shallow and this may limit snowfall prior to sunrise in the central Wasatch. Moisture and instability deepen with frontal passage, which probably represents the surest bet for this storm. Post-frontal currently doesn't provide a period of moist, northwesterly flow air immediately behind the front, but things get more interesting later Wednesday night and Thursday morning as discussed more below.
Through 9 PM Wednesday, the NAM generates 0.32" of water and 6.7" of snow at Alta, the GFS 0.51" and 7.8." After that, the models diverge some. The NAM is bearish on the overnight northwesterly flow through Thursday morning, producing little to no snowfall, whereas the GFS is bearish, giving some love, possibly in the form of what it thinks is lake effect, to the central Wasatch.
At Alta, the GFS generates about 0.25" of water and, due to the large snow-to-liquid ratos, 6 inches of snow through 10 AM Thursday. The Euro is somewhere in the middle.
Putting all of this together, I anticipate 5-10" at Alta through tomorrow (Wednesday) evening, most coming during the day tomorrow with the frontal passage. After that, there may be a break, with the potential for some cold smoke falling later Wednesday night if conditions are right. Keep your fingers crossed.
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