Avalanche forecast

Salt Lake

Issued Dec 12, 2022valid to Dec 13, 2022Utah Avalanche Center

Avalanche danger

Alpine
Treeline
Below treeline

Out of date — this forecast expired 4 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

The avalanche danger is HIGH on mid and upper elevation northwest through east aspects where natural and human-triggered avalanches may break down 2-4' deep and over 200' wide, failing on a persistent weak layer of faceted snow. The avalanche danger is CONSIDERABLE at lower elevation northwest-east aspects and on mid and upper elevation west-southeast aspects. The avalanche danger is MODERATE at lower elevation west-southeast aspects.

Today is a day to avoid traveling on slopes over 30 degrees or connected to slopes over 30 degrees.

Avalanche problems

Persistent Slabs
N
NE
E
SE
S
SW
W
NW
Alpine
Treeline
Below treeline
Likelihood
Very Likely
Size
3
There is plenty of weak sugary faceted snow (persistent weak layer) scattered on almost all aspects and elevations throughout the Wasatch Range. This persistent weak layer has now been buried under wind drifted snow in upper elevation terrain and capped by storm snow in the lower elevation wind protected areas. As we saw from the close call outside of Spanish Fork and from this observation in Big Cottonwood Canyon, I would be just as cautious in steep lower elevation terrain that harbors this weak layer.

However, what varies is the slab (the snow sitting above the weak layer). In sheltered locations, this slab might only be 10-15" inches deep, and in areas where the wind has loaded the slope, the slab could be anywhere from 1-4' feet deep and hard as a rock. In any case, we have dangerous avalanche conditions, and you can still trigger a season-ending slab avalanche failing on a persistent weak layer.

Avalanches are slightly less likely on solar aspects because of the prescence of ice crusts.

Today is not the day to tease this weak layer. The good news. This problem will go away with consistent snowfall. Remember, it's a long season, and it's shaping up to be an epic winter, don't ruin it now by getting injured or killed in an avalanche.
Storm Slabs
N
NE
E
SE
S
SW
W
NW
Alpine
Treeline
Below treeline
Likelihood
Possible
Size
2
As of early this morning ski area patrol teams are reporting dry loose avalanches within the storm snow. This will be a short lived problem as new snow instabilities will settle out.
Wind Slabs
N
NE
E
SE
S
SW
W
NW
Alpine
Treeline
Below treeline
Likelihood
Likely
Size
3
These slabs of wind drifted snow can be soft or hard. The hard wind drifted snow might be camouflaged, look for stiff hollow drum like conditions under the new snow. Be on the lookout for cross-loaded terrain features or drifts well off the ridgelines.

Remember, any wind slab avalanche that you trigger has the potential to step down into deeper weaker layers in the snowpack, creating a much more dangerous avalanche.

Recent Activity

Overnight there was a natural avalanche cycle reported from mid Little Cottonwood Canyon during periods of higher precipitation rates. I expect that there were more avalanches in other areas during the highest snowfall rates.

Skier Triggered avalanche on Friday, 12/9 in the Spanish Fork area. They were caught, carried, and partially buried against a tree. Details are limited, but you can find them HERE.

Snow and Weather

The National Weather Service has issued a Winter Storm Warning that will last through Tuesday at 5:00 pm.

It is currently snowing in the mountains. Mountain temperatures range from the low 20's F at the trailheads to the single digits F at 11,000'. Southwesterly winds are blowing in the mid teens gusting to the low 20's MPH at the 9000' and 11,000' ridgelines.

Storm Totals:

Upper Cottonwood Canyons 14-17" snow 1-1.3" water
Park City Ridgeline 8-10" snow 0.5-1" water

For today we are expecting snow showers with up to 6" of snow throughout the day, temperatures from 18-22 F and 9000' ridgeline winds southwest 20 gusting to 30 MPH and 11,000" ridgline winds southwest 25 gusting to 45 MPH. Winds will shift to the west and decrease after noon.

Additional Info

Mark Staples has also written a season summary HERE.

Check out this forecast discussion.

Special Avalanche Bulletin

STRONG SOUTHERLY WINDS, COUPLED WITH HEAVY SNOW OVERNIGHT HAS CREATED RISING AVALANCHE AVALANCHE DANGER OVER THE LAST 24 HOURS. LARGE, DANGEROUS AVALANCHES ARE LIKELY ON NORTHWEST-NORTH-EAST FACING AVALANCHE TERRAIN. AVOID BEING ON, UNDER, OR ADJACENT TO STEEP WIND-DRIFTED SLOPES AND TERRAIN STEEPER THAN 30 DEGREES.

General Announcements

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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.

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