Saturday Afternoon update:
18z NAM is in as well as 12z GFS and ECMWF. If anything, models are even more optimistic with precipitation amounts in the storm. Temps in most recent model runs are also just a touch colder — so hopefully snow levels stay down closer to 7,000 feet tomorrow. Not too much to update. Amounts thru Monday evening still look good… Upper part of the Cottonwoods could easily see over 2 feet. Also, the high elevations north of I-80 could see similar amounts above 8,000 feet. PC should see a bit less, but still 10-16″ possible on the upper mountain. Base elevations are much more uncertain, especially the lower resort bases, which could see rain for parts of the event. One thing is for sure… We are going to see a lot of precip between now and Monday afternoon.
A bit of lower density snow has been falling today. When the temps warm and the snow gets heavier tonight, it will create an upside down scenario. Avalanche watches/warnings have been hoisted. I would recommend NOT venturing into the backcountry until this snow has had a chance to settle, but if you do, please please please consult the UAC beforehand.
In other news, the GFS aligned closer to the EC with regard to the Christmas storm. I’m still not sold until I see a couple more runs, but at this point a Christmas powder day is still in the cards. More info in the AM…
Until then, enjoy this latest NAM projecting MASSIVE snowfall for the area through Monday evening…
A weak system passed through overnight and dropped 0-4″ of snow in the Wasatch. A break today before the fire hose turns on tonight with an extended period of precipitation lasting into Monday. Another system for Christmas could bring the region some snow on Christmas Day.
All systems are go for our Atmospheric River event starting tonight and lasting through Monday. We do know there will be lots of moisture. The big problem will be snow levels. I just spent the last 20 minutes trying to pin down snow levels and I don’t think I’m any closer. Temps at 11,000 feet are likely to rise to near freezing. The snow level will be substantially lower than the freezing level, however it still may reach 8,000 feet at times tomorrow. In these patterns in the past, we’ve seen it go both ways. In some events, the snow levels have come in lower than anticipated. In other events higher. This will have a huge impact on how much snow we get.
Snow totals at 8,000 feet will likely see 2″ of liquid contained in only a few inches of sloppy snow. The base elevations of PC will likely be mostly rain tomorrow. The upper elevations (above 9,000 feet) is where the substantial accumulations will be. The upper portion of the Cottonwood resorts could see up to 2 feet of snowfall by Monday evening. The upper portion of PC resorts could be looking at a foot or so during the same period. It’s going to be very interesting to see how high snow levels rise tomorrow, if they stay low, this will be a much better event. In any case, the snow that does fall is great base-building snow. However, it is not the best snow for skiing by any stretch of the imagination. The other factor will be wind. Strong ridge top winds will gust throughout the event out of the west and northwest.
Snowfall totals from the 06z NAM for the Upper Cottonwoods:
A break on Tuesday and Wednesday as the jet retreats northward.
The Christmas Day system looks totally different in the two major models. The GFS brings only a weak cold front through the area that brushes northern Utah. In this scenario, we’d only see a couple inches of mountain snowfall and maybe a dusting in the valley, mostly late in the day on Christmas. The ECMWF (Euro) is much stronger and deeper with this system and would bring several inches Christmas morning to the valleys with up to a foot in the mountains. The Canadian model is somewhere in between. I have very little confidence but my guess is that we’ll end up somewhere in between. So probably a 6″ storm or so for most mountains with a chance for a quick inch or two of snow in the valley on Christmas day.
It looks like the ridge of the coast will continue to strengthen after Christmas. We’ll have a chance for a weak system to dive down into the area at some point early next week. Models are hinting at the potential for a breakthrough of the westerlies again after the New Year. Something to watch…