If you want a characterization of the snow that has fallen over the last couple days, here are a couple of precipitation/snow totals from the Wasatch since Friday evening:
Tony Grove (Northeast of Logan, West of Beaver Mountain): 18" of snow, 4.1" of snow water
Ben Lomond Peak (Just north of Ogden): 16" of snow, 4" of snow water
Snowbird: 11" of snow, 2.2" of snow water
That's some dense snow (and it is snow, these are all sites above 8000 feet). This is combined with some raging winds at ridgeline - both Mt. Baldy (Alta) and Hidden Peak (Snowbird) have measured gusts above 90 mph. Hostile is one word to describe these conditions, another term would be "base-building." Regardless, once things get opened up tomorrow (note, as of this being written, Little Cottonwood will be closing at 8pm and control work will be performed tomorrow morning with a tentative road opening at 8:30am), it should be creamy happiness all over the slopes.
Widespread snowfall should be tapering off tomorrow around midday, with scattered showers lingering through until lifts close. Tuesday and Wednesday will be relatively clear, with brief ridging and southerly flow throughout the region. This will give time for all of the sweet leftovers to get tracked up before the anticipated Christmas storm.
So what is that going to bring? Well, currently the models have the timing being just before midday on Thursday for most of the Wasatch. Snowfall should be heavy with and immediately following the frontal passage, with totals around 6-10" in most locations. One thing to note is that this will be a CHILLY storm (ridgeline temperatures in the GFS pushing -16C) so Thursday could be a thin shell kind of day in the morning with several layers being added by the time lifts close. The post-frontal environment does have the potential to initiate some lake-effect convection if the models hold, so favored locations downstream of the Great Salt Lake could see another 3-6" (or more) on Friday, while other areas should see little post-frontal precipitation.
The models remain inconsistent after this Christmas Day storm, with the 18Z GFS passing us by until after New Year's Day...regardless, Happy Holidays, and enjoy Ullr's awesome Holiday gifts!
The decent 3-6 inch precursor has ended and the first snowbands of the main event are just now entering the salt lake radar! A much needed deluge is on the way.
The forecast for this storm is easy in that all models are agreeing on evolution and amounts and that they have been consistent over the past few days. The forecast is clouded, however, by the fact that Utah has never seen a storm like this so we don't really know how the models will do and what areas will be most favored.
The setup is simple. A atmopsheric river with subtropical orgins is entering the interior west through the low passes of Oregon and Northern California. This moisture surge, coupled with a very strong jet aloft, will bring an unprecedented flux of moisture into northern Utah in northwest flow. As many of you know northwest flow usually means big snows for areas like the cottonwoods and powder mountain, but usually northwest flow is associated with colder temperatures and drier conditions. So this storm is a unique combination of very moist and warm air coupled with northwest large scale flow.
The lower resolution global models are producing 2-3 inches of water by Tuesday morning over the mountains and the higher resolution models are even higher than that. Try 4-7 inches of water! Ridiculous right? Maybe, but we dont really know.
Unfortunately the air is very warm and snow levels will be very high. 7500-8000 feet. That means snow will be very dense and have trouble accumulating. With all that said here is what I am thinking
Snow starts tonight around midnight and quickly becomes intense. Snow levels may start off around 6500-7000 feet, but quickly rise another 1000 feet during the day Sunday. Snow levels come down Sunday evening as some cold air moves in and lower density snow is possible by Monday morning with snow valleys falling below 6000 feet. The snow ends Monday evening
cottonwoods above 8000 feet: 20-36 inches
park city below 8000 feet (lower half of resorts): a few inches Monday, otherwise rain
park city above 8000 feet: 10-20 inches
snowbasin and powder mountain above 8000 feet: 18-32 inches
sundance: rain with an inch or 2 possible monday
Monday will be the best ski day with ligher, right side up snow. The upper mountain runs will ski better than the lower runs. I would lap little cloud at Snowbird or the angle station at Alta.
Still some uncertainy with the strength of this storm, but this storm will be much colder with snow for all. Looking like at least 6 inches for the typically favored resorts, with the possibility for quite a bit more than that.
No model consensus whatsoever. Could be active or dry. Does look colder at least
Before I get to the upcoming Atmospheric River set to blast the Wasatch starting later this weekend, I'll hit the short term real quick.
With cold temps and a quick-hitting shortwave scooting through Utah this (Friday) evening, I'm expecting a burst of nice low-density snow in the mountains. I'll go 3-6" for the upper Cottonwoods, 2-4" for the PC resorts, and 3-5" elsewhere.
Now for the good stuff! Nature's firehose will be cranking up beginning late Saturday night, with precip rates and wind speeds increasing into Sunday morning, and the storm ending late Monday night. There will not be a ton of large-scale lift provided by the atmosphere but the sheer amount of water being transported in the nuking upper level winds, and then being forced to rise over the Wasatch, will provide all the ingredients to drop some serious precipitation. This is an Atmospheric River. So what will the conditions be like on the ground?
-Snow levels will be high: getting as high as 8,000ft on Sunday. The bases of many resorts will get rain.
-Winds will be howling Sunday morning through Monday morning
-Snow will be of the Sierra Cement variety. I wouldn't be surprised to see periods of 5:1 snow-water ratios
-Avalanche conditions will be quite dangerous in the backcountry
As for snowfall totals, I'm going to stick with exactly what Trey went for yesterday. Near the snow line, these totals won't be valid of course, but I anticipate these amounts at mid-mountain and above. Trey went for 18-36" in the upper Cottonwoods and northern Wasatch, with 10-20" on the PC side (above the snow line). Most important in these kinds of storms though is the amount of liquid equivalent in the snow that will fall...important for covering up rocks for skiers, and for storing water in our snowpack for lakes and rivers. I'm anticipating 3-5" of liquid in the upper Cottonwoods and Logan area mountains...that's a lot of water from one storm.
So it's gonna be a wet, warm, and windy storm...and one we definitely need. As Trey said, get out there and surf that beautiful new snow!
Long Term also still looks good for a nice cold storm Christmas Day by the way. Santa put Utah on the nice list!!!
Looks like we were able to squeeze a couple inches out of some snow showers this morning. Forecaster Peter Veals was reporting 1-2" on the ground in Upper Little Cottonwood, which helped freshen things up a little. Looking ahead we have a very exciting forecast.
A strong upper level jet max will slam into the Pacific Northwest this weekend bringing with it a very moist/unstable airmass. This will help place Nrn Utah in a favorable region for prolonged, strong northwesterly flow. Several favorable ingredients will likely come together to provide an extended period of snow at higher elevations:
1. Strong jet max penetrating the inner-mountain west - 160 knot jet max
2. Moist northwesterly flow in the mid-upper levels - favorable for additional orographic enhancement particularly in the Cottonwoods and westerly/northerly facing aspects.
3. Long duration - 48 hours
A few concerns also exist, though:
1. Warm airmass - Snow levels will be 7500-8500 feet. Cooling effects during heavier precipitation will be able to overcome this at times, though.
2. Jet location - Nrn Utah will be more on the Anti-cyclonic side of the jet. Preferred location is directly underneath and just north of the jet max.
With all this said through Tuesday I'm conservatively expecting 1.5 - 3 FEET in the Upper Cottonwoods and resorts in the far North like Beaver Mntn (particularly above mid-mountain where snow ratios will be slightly better). 10 - 20 inches should fall in the Park City area at mid-mountain and above. Base locations may see periods of rain and snow due to the warm airmass. Unfortunately areas farther south will be the big losers for this storm cycle. Totals will be marginal at best with < 6 inches at resorts such as Sundance, even at the highest elevations.
How will it ski? Due to the warm air mass snow densities will be quite high (probably average 7:1 - 10:1 above 9000 feet). So while we aren't talking blower pow, you should still be able to surf the higher density snow with your fatties. MOST importantly, this is adding much needed water to the overall snowpack and coverage should drastically improve.
The Cottonwood resorts were able to squeeze all of 1 inch out of the very weak disturbance last night and cloudy skies have been the rule today. Matt L was thinking that there might have been more, but alas, it was only enough to produce some wisps as you cruised down the groomers. A shearing, negatively tilted trough will come onshore in California tonight, adding more to their much-needed totals.
The trough really falls apart tomorrow though, and the moisture and lift just aren't going to come together for Northern Utah. I think an inch or less is a good bet Wednesday. Like Matt L mentioned, Brian Head might be able to get to 6 inches or so as they will have more moisture to play with. The shreds of the trough will hang around Thursday, bringing grey skies and maybe another inch to the Wasatch. Beaver Mountain and the Logan-area mountain will do better Thursday, with 1-4 possible by Friday morning.
Looking forward from Friday, the large scale pattern will begin to shift from what we have seen this week. According to the current GFS, the polar jet over the eastern Pacific will become fairly static as a deep long-wave trough sets up over the Central Pacific. Such a pattern will keep the proverbial firehose pointed right at Oregon and Washington. Enough of this moisture will make it inland that Northern Utah could do pretty well in the moist WNW flow from Sunday to next Tuesday, albeit with high freezing levels. The ECMWF ensemble likes it too, with virtually all the ensemble members on board with the idea of a strong, wet westerly jet hitting the northwest US.
The only question is whether we will end up too far south to get it! This setup lookssimilar to the one that really gave our season a kick in the pants last February, where the Cottonwoods did well, low elevations got rain, and areas from Logan, UT to the Tetons just got hammered.
In short, don't bank on it yet, but the 5-7 day outlook is hopeful.