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Forecast for the Salt Lake Area Mountains

Trent Meisenheimer
Issued by Trent Meisenheimer on
Monday morning, December 23, 2019
A scary MODERATE AVALANCHE DANGER exists for triggering an avalanche 2-5' deep on steep northwest to east facing slopes at the mid and upper elevations. Avoid steep, thin, rocky terrain. A more widespread and tricky MODERATE danger exists for wind drifted snow on a variety of aspects found at the mid and upper elevations. These hard windslabs are unmanageable and should be avoided.
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Special Announcements
Final report for the Dutch Draw avalanche fatality is available HERE. Consider donating to the Matt Tauszik Memorial Fund to help his wife and young son.

Stocking Stuffers: Thanks to the generous support of our Utah ski resorts and Ski Utah, we have discount lift tickets available. All proceeds from these go towards paying for avalanche forecasting and education! Get your tickets here.
Weather and Snow
Under partly to mostly cloudy skies the southerly winds continue to blow across the mid and upper elevation terrain with speeds of 15-30 mph gusting to 45 mph, depending on your location. Mountain temperatures hover in the upper 20's to low 30's °F. For today, we will continue to see thick clouds stream overhead and southerly winds, however, the wind won't be as strong as yesterday. A series of weak storms will impact the state beginning overnight and lasting into Thursday. This system doesn't look all that impressive for northern Utah, but, we could see 5-10" of new snow by Friday morning.
Warm temperatures and strong winds have taken their toll on the snow surface. Southerly aspects and low elevations now have sun/heat crusts. Upper elevation exposed northerly terrain is a moon scape with hard wind board scattered around the slope. Soft settled powder remains in the mid and upper elevation wind and sun sheltered terrain.

Our Week in Review - summarizing the significant weather and avalanche events of the past week - can be found here.
Recent Avalanches
A backcountry skier triggered a hard wind slab off Rocky Point in upper Big Cottonwood Canyon. The wind slab was 2.5' deep and 45' wide. The skier was able to move out of the way of the avalanche and was not caught. South Monitor along the Park City Ridgeline avalanched naturally overnight (Saturday) from the strong southerly winds loading the slope. This avalanche was a repeater and roughly 100' wide failing to the ground. It ran full track to the bottom taking out old ski tracks.
Yesterday, a skier found a hard wind slab that broke around him/her 1-3' deep and 175' wide. They were caught and carried. They deployed their airbag and was buried up to their armpit in debris. No injuries. The slope angle was measured at 31° degrees.

All other avalanches and observations are listed HERE.
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Avalanche Problem #1
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
Steep, rocky terrain should still be avoided in the mid to upper elevations on northwest to east facing slopes. The additional wind loading will add stress to the poor structure and it is possible that skiers, snowmobiles, and cornice-fall, etc, in the right spot may trigger a devastating avalanche. Danger Trend: Steady to Increasing
Currently, there is a very strong slab of snow sitting on top of weaker (faceted) snow at the base of the snowpack. When it comes to avalanches we need two things: Initiation and propagation. While the extended column test (ECT) remains the bread and butter test for the backcountry travelers we are now starting to see ECT scores that show no results (no propagation) across the buried weak layer. The ECT test is one of the best tests to perform on the snowpack as it shows both initiation and propagation while performing the test. However, it has one weakness, when the slab becomes very strong it can be very hard to initiate the weak layer by hitting the top of the shovel blade. Just as we are riding across the snow surface it's hard for our weight to effect the weak layer.
Initiation or triggers can come in many forms: Loading (adding weight) by wind or snow, skiers, snowboarders, cornices, explosive, to name a few.
The Propagation Saw Test (PST) only tests propagation of the weak layer (no initiation). In the video below you can see the weak layer propagate up the column followed by the slab of snow crashing down. What does all this mean? well, if you are unlucky enough to initiate or trigger the avalanche it's clear to me that you can still propagate a crack through the weak layer and cause a very large and deadly avalanche. The probability is low, but the consequence is high.
Video: Propagation Saw Test - showing the weak layer and slab.
Avalanche Problem #2
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
The southwest winds have and will continue to scour and erode any available snow and deposit it in the form of soft and hard wind drifts in the mid and upper elevations, even in odd and unusual locations. Yesterday, we had two people trigger hard wind slab avalanches at the upper elevations. We also had one skier trigger a hard wind slab, taking a ride in the avalanche. This should be a hint that these drifts are not to be messed with.
In some areas, these drifts may land on weak snow surfaces formed over the past week and may be surprisingly sensitive and possibly triggered from a distance. These areas are more likely found in the sun and wind sheltered terrain where the snow surfaces are susceptible to decay. Wind drifts are often smooth, scalloped, and rounded . Soft wind slabs you're "in the snow" with your sled or skis; hard wind slabs you're "on top of the snow". Hard slabs are often trickier because they allow you to get well on to them before they collapse. For today, continue to look for and avoid rounded, pillowy, or hollow sounding snow.
* Any wind slab avalanche triggered does have the potential to pull out a much larger avalanche in areas that have a persistent weak layer present.
Additional Information
General Announcements
This information does not apply to developed ski areas or highways where avalanche control is normally done. This forecast is from the U.S.D.A. Forest Service, which is solely responsible for its content. This forecast describes general avalanche conditions and local variations always occur.