UDOT PLANNED AVALANCHE CLOSURES!!

Forecast for the Salt Lake Area Mountains

Mark Staples
Issued by Mark Staples for
Wednesday, January 16, 2019
Today with new snow and some S and SW winds, the avalanche danger is MODERATE for triggering a shallow slab of wind-drifted snow at upper elevations. There could be a few isolated wind slabs at mid elevations but these are much less likely to exist. At mid and low elevations the danger is LOW where avalanche conditions are generally safe.
Avalanches breaking 2-3 feet deep on a persistent weak layer are unlikely today but remain a concern at mid and upper elevations especially with more snow coming that may start to awaken this layer.
9 a.m. UPDATE: Shallow natural avalanche spotted on a south aspect near Cardiff Pass in Little Cottonwood Canyon. It broke about 150 feet wide and maybe 4 inches deep within the new snow. This type of instability could settle down by this afternoon, but watch for it this morning while snow is still falling OR if the wind is blowing and loading a slope.
Low
Moderate
Considerable
High
Extreme
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Special Announcements
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Weather and Snow
It's snowing this morning with about 4-5 inches of new snow in the upper Cottonwood Canyons and 2-3 inches along the Park City ridgeline.
Temperatures are mostly in the lower 20's F. Below 8000 feet temperatures are in the upper 20's F.
Winds shifted from the S to SW and at ridgetops were blowing 10-15 mph with gusts of 20-30 mph.
Today, temperatures at upper elevations should warm into the upper 20's F and at lower elevations into the mid 30's F. The strongest winds will be this morning and decrease some this afternoon. Snow should continue this morning but taper off by midday. Skies will stay cloudy and more snow returns tomorrow morning.
There was a brief period of warm temperatures and mist up to nearly 10k feet yesterday. This mist formed a very thin crust now buried under the new snow, but you probably won't notice it skiing or riding because it was so thin. Photo shows icing on a ski pole yesterday around 1 p.m. from the mist. Below about 7800 feet, the snowpack was very warm an the surface was even a bit wet.
Recent Avalanches
There have been no reported avalanches during the last two days. There were some slabs of wind drifted snow triggered over the weekend.
On Sunday there was a skier triggered slide in American Fork Canyon. We don't have an avalanche report to view on this one, but it broke on a thin layer of weak facets, about 2 feet deep, on an east facing slope at 9600 ft. It was about 250 feet wide.
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Avalanche Problem #1
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
With new snow this morning and S and SW winds, look for fresh slabs of wind-drifted snow. These can either be formed by wind-loading from the top of ridges OR cross loading along the edges of gullies and sub-ridges. The simplest way to deal with this problem is to look for it and then avoid it. Ski cutting may be an option but it is a high risk maneuver that often surprises professional ski patrollers who have a lot of practice doing it. There are older wind slabs covered by new snow. These have most likely stabilized but a few could remain sensitive. Places with new wind slabs are likely places with older wind slabs.
Image below of top loading.
Image below of cross loading
Avalanche Problem #2
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
Yesterday my partner and I skied from Red Pine to Hogum Fork. We identified and avoided areas of wind drifted snow. A harder problem to avoid is a persistent weak layer of facets. There are some near the ground, but these have not produced an avalanche in a long time. Periods of dry, cold weather in mid December and early January formed a layer of sugary facets that are now buried 2-3 feet deep.
The only way we could find this avalanche problem was by putting our shovels in the snow. We dug quick snowpits and performed extended column tests (how to video). This test can help find weak layers when the colum breaks under your shovel. If it breaks across the column (propagates), that is a bad sign.
These persistent weak layers have been mostly dormant, but Sunday's slide mentioned above is a good reminder that they are still lurking and can produce avalanches. With more snow coming, these layers will get weight on them which means more stress which means slab avalanches will become more likely.
Additional Information
The Wasatch range has a complex snow surface for the incoming storms to land on - near surface facets, surface hoar and a variety of weak crusts and hard old wind slabs with facets above and below. If you’re out and about today, see how the new snow has bonded to yesterdays snow surface.
If you’re heading further afield, here’s a great observation from the Oquirrhs.
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.