Sunday PM update:
This afternoon’s model runs have generally been consistent with this morning’s. The GFS does not split the system nearly as bad as it did in the 00z run last night, but it still concentrates the majority of the precip on central and southern Utah. The EC and the GEM are farther north with where they stall the front, showing the best precip from about I-70 north to I-80. Where this boundary stalls is crucial to how much snow we get in the Wasatch, which is why snow accumulations are still uncertain. Still looks like accumulations through Wednesday will be 6-12″ in the Wasatch south of I-80 with 4-8″ north of I-80. Northwest flow through the end of the week should add a few more inches on top of that. If everything comes together just right, we could definitely see more snow than forecasted, but with so much uncertainty, it is better to air on the conservative side. Full update in the morning…WSF
Significant winter storm still on track, however there are a few changes to the going forecast. Today and tomorrow we’ll see mostly cloudy and breezy conditions with a chance for a few high elevation snow showers ahead of the main system.
Last night’s 00z run of the GFS was not kind to us. It reverted back to an older solution in which the trough splits as it moves south into the area tomorrow. This would send a good amount of the energy east through the northern rockies. The other portion of energy would drop into Central Nevada before ejecting trough Southern and Central Utah. Hence, northern Utah misses the bulk of the action. In the scenario, the Wasatch would still see snow, but amounts would not be nearly as high.
This morning’s 06z GFS still showed split, but not nearly as much. The NAM, GEM, and Euro have all showed a very slight trend toward that split as well in their latest model runs, so it looks like the models might be zeroing on that solution.
The other change is that models are all speeding up the front now and how fast it gets to Utah. Yesterday, it looked like snow would develop late Monday night into Tuesday AM. Now it looks like snow will develop Monday evening and be heaviest overnight. This changes the best day to go skiing. Yesterday I would have said Tuesday was a storm day with Wednesday being the best powder day. Now it definitely looks like Tuesday will be the money day.
As for accumulations, that is such a tough call with this system. Right now, it looks like Central and Southern mountains will do very well with 10-20″ possible by Wednesday night. The Wasatch is right on the border between where the best snow looks to set up. I still think that 6-12″ south of I-80 is likely by Tuesday night. North of i-80 might get the short end of the stick, but 4-8″ still seems likely. Remember, this is only for the main front, additional accumulations of 4-8″ are possible for all of the Wasatch through Friday as additional waves fire up more snow showers. That would put total accumulations by Friday at about 10-18″ for the Cottonwoods, 8-14″ for PC and 8-14″ as well for Snowbasin/PowMow. Usually I’m fairly confident when forecasting snowfall amounts — this is not the case with this system. Don’t be surprised if your location sees more or less than listed, for right now this is just my best guess.
The uncertainty around this system right now is reflected in the NWS as well. They put almost the entire state under a Winter Storm Watch this morning, but do not give any estimates for snow other than… “significant accumulations are possible”.
Beyond the work week there is promising news, most models drop another system into the area next Sunday-ish (Dec 8). The timing keeps changing, but it looks like we’ll have another shot at additional snow. Additional storms look likely to impact the West beyond that as most models show the eastern Pacific ridge retrograding and opening up the storm door.
Keep in mind also, that it is going to be very cold from Monday night through the weekend, so all ski resorts with the capabilities should be making tons of snow as well. We should get a lot more terrain open this week. Despite all the uncertainty in how much snow we will get, this is still a very good event for Utah skiing.
You can be certain I’ll be making updates today as new model runs come in… so check back!