Forecast for the Salt Lake Area Mountains

Issued by Drew Hardesty for Wednesday, December 5, 2018 - 5:05am
Areas of CONSIDERABLE danger exist at the mid and upper elevation northwest through east facing slopes. The danger is more pockety in the upper elevation west and southeast quadrants, but no less dangerous. Human triggered avalanches 2-3' deep are probable and may be triggered at a distance. Localized areas of MODERATE danger exist for new and developing drifts in steep wind exposed terrain.
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Special Announcements

We have a couple of fun events coming tonight and tomorrow in Salt Lake and Park City.
Tonight - join Greg Gagne and Andrew McLean at Rocksteady Bodyworks in Holladay for an open discussion of Recreating in a New Zone to learn about how the evaluate snow conditions when traveling and skiing in a new zone.
Tomorrow night at the Park City Library, Ascent Magazine presents The Slide Show, a celebration of the coming of winter with video and photo presentations from some of the hardest working trail breakers around.
More info about these events HERE.
Weather and Snow
In his report from Mt Raymond yesterday, forecaster Greg Gagne wrote, "The sun was ok, but 1 day was enough and I'm ready for another storm." I suppose he'll get his wish, though the current storm moving overhead will leave him (and the rest of us, for that matter) feeling short-changed. We'll be lucky if we squeeze a couple inches out of the southern-track storm. On the other hand, mountain temps are on the order of 15°F warmer than they were at this time yesterday with most stations - at 4am - already in the mid-teens. Southwest winds have bumped overnight and blow 15mph with gusts to 20. Skiing and riding conditions yesterday were - again - nothing short of sublime, but the southerlies will have a breakable sun-crust that'll likely remain intact with today's temps and sky cover. Oh well. Low angle shady slopes will still be divine.
Click the animated weather map below and wave as the storm off the coast of California ejects inland and moves through to the south -
We'll have overcast skies with a few 'traces' of snow with high pressure building back in for the weekend. Temps will be in the 20s with westerly winds 20mph from the west and southwest, diminishing by later this evening.
Recent Avalanches
In their outing into White Pine of LCC yesterday, Mark Staples and Andrew McLean described getting a massive collapse, or whumph, in the snowpack which shook small trees 50' away. Quaking aspens, perhaps. This, of course, is a classic bull's eye sign of an unstable snowpack and a good and easy reminder to remain on low angle slopes. We did not, however, hear of any human triggered avalanches into the old snow yesterday; however, this was not the case for the snow safety teams at the ski areas. Even 'minor' explosive control work produced large avalanches - some stepping through the October crusts to the ground - on upper elevation northwest to northeast facing slopes.
On Mt Raymond yesterday, Greg and his partners triggered a small 6" new snow pocket on its steep south face and reported some minor sluffing in the weakening low density surface snow.
Confused about locations and names? Check out the Wasatch Backcountry Skiing page (and app).
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Avalanche Problem #1
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
We've had human triggered avalanches stepping into the old October snow 2-3' deep nearly every day since Thanksgiving with at least a dozen since December 1st. Cracking and collapsing remain the rule and not the exception. These are the easy decision-making days because evidence is high and uncertainty is low. Enjoy it while you can: those days will soon be coming to an end. To be clear, we'll soon be trending toward what we call "Scary Moderate" where cracking and collapsing are rare and human triggered slides into the old snow 2-3' deep are isolated, pockety, and surprising. But not in a good way. It's the cost of slow stabilization. It's the cost of old pre-existing snow from October. In the coming days, we'll outline some snow assessment tools and terrain management tricks to deal with the 'low-probability...high-consequence' regime. Stay tuned.

For now, it's night and day in regards to aspect and avalanche conditions. Grab your compass before heading out into the backcountry. Greg explains more below -
Avalanche Problem #2
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
Be on the lookout for some fresh but shallow wind drifts along the lee of ridgelines and around other terrain features in the higher elevations today. These drifts may be particularly sensitive and possibly triggered from a distance.
General Announcements
This information does not apply to developed ski areas or highways where avalanche control is normally done. This advisory is from the U.S.D.A. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur.

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