Avalanche forecast

Salt Lake

Issued Feb 21, 2023valid to Feb 22, 2023Utah 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Out of date — this forecast expired 4 years ago.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

This morning the overall avalanche danger is rising to MODERATE as the storm develops, but it may spike to CONSIDERABLE during periods of heavy snowfall late this afternoon and early this evening. Today's new snow may produce soft slab avalanches or long-running sluffs. Additionally, the elevated winds may create unstable slabs of wind-drifted snow at mid and upper elevations. Pay attention to changing weather patterns, if the storm comes in sooner than anticipated the danger will rise sooner than anticipated. Human-triggered avalanches are possible. Natural avalanches are unlikely, but possible during periods of heavy snowfall rates or stronger winds.

Avalanche problems

Wind Slabs
N
NE
E
SE
S
SW
W
NW
Alpine
Treeline
Below treeline
Likelihood
Possible
Size
2
Winds remained elevated overnight, with gusts near 50 mph this morning. The high winds, in combination with new snow will continue to form fresh slabs of wind-drifted snow along all aspects at upper elevations. These wind drifts will be generally shallow, but could be sensitive to the weight of a rider today. Look for obvious signs of wind-drifted snow, such as pillow-shaped slopes, cracking and whumpfing, and avoid those slopes.
Storm Slabs
N
NE
E
SE
S
SW
W
NW
Alpine
Treeline
Below treeline
Likelihood
Likely
Size
1
The issue is simple today, as the snowfall intensity increases, the avalanche danger is going to increase as well. The cold front moving in is predicted to have periods of very high snowfall rates, as well as overall high snowfall totals. Once the snowfall begins, I expect to begin seeing shallow new snow avalanches in the backcountry today. With the generally warm temperatures today, I expect the new snow to be fairly cohesive and should break as a shallow soft slab, but, fast running sluffs are also likely today, especially in the upper elevations.

The type of avalanche will come down to how quickly the new snow bonds, versus how quickly the snow is falling from the sky. Watch for signs of instability such as cracking and sluffing. Even a small slide can have serious consequences in big, steep terrain or if you’re above cliffs.

Today, the sensitivity of the new snow largely depends on the rate of snowfall. During higher rates of snowfall (greater than 2 inches per hour) avalanches will be easier to trigger. Periods of snowfall exceeding 2 inches per hour are possible during the day today, especially late this afternoon and early this evening. During those periods of high snowfall rates, small natural avalanches may be possible. Pay attention to changing weather and increased snowfall rates.

Recent Activity

Yesterday, multiple human-triggered avalanches were reported in the backcountry. The majority of these avalanches failed as shallow slabs of wind-drifted snow on the old snow interface. See one observation from Jaw's yesterday on a Northeast aspect near 10,200'. Easily large enough to knock someone off their feet. Photo (L. Gangi-Wellman)

Find all recent avalanche activity HERE.

Snow and Weather

This morning, the skies are broken. Mountain temperatures are sitting in the upper teens and low 20s F. Along 9000' ridgelines winds are blowing primarily west-southwest at speeds of 10-20 mph, with gusts between 30-40 mph. At 11,000 feet, the winds are west-northwest gusting up to 50 mph.

Today, one of the stronger storms of the winter will begin to move through the area. A winter storm warning went into effect this morning around 4 AM and will run through 5 AM Thursday. Throughout the morning expect snow showers to increase, turning to periods of consistent snow after noon. By the late afternoon, between 3 PM - 5 PM a strong cold front will move through the area bringing very intense snowfall rates, up to 2.5-3" snowfall an hour. Temperatures will climb into the upper 20s and low 30s F. Winds will remain elevated from the west-southwest blowing 20-30 mph at 9,000' ridgelines, and gusting up to 70 mph at the 11,000' ridgelines. Snow totals by this evening will be between 9-16" of new snow (0.55-1.1" of water).

Overnight, the storm will only continue to intensify. Snowfall remain heavy overnight, and winds will transition more northwesterly. Overnight snow totals could be between 10-20" of new snow (with 0.9-1.5" of water), with the high-end totals being closer to 25" of new snow with almost 2.0" of water.

Storm totals continue to rise, looking to be somewhere between 32-42" of new snow (and 2.10-3.00") by Thursday morning.

Surface conditions have greatly improved with the new snowfall. Out of the wind zone, in protected terrain, the new snow will still be soft and the riding should be enjoyable.

Additional Info

Forecaster Corner: The incoming storm is impressive. Trent described it as "a beast of a trough", the NWS is calling it one of the stronger storms of the Winter. The bulk of this storm will push into Northern Utah Tuesday afternoon and will last into Thursday for the Wasatch Range.

With the new snowfall, comes a lot of uncertainty. Before Sunday's new snowfall, we had a wide variety of snow surfaces in the backcountry from stout wind board, to firm sun crusts, to a few pockets of lingering cold snow. Along with overall variable snow surface conditions, observers had also begun to note that the snow surface was weakening and small grain facets were present in some areas. See Greg's observation from Mill Creek Canyon.

What does this mean for avalanche conditions? Well, I am unsure how Sunday's new snow will overall bond to the variety of surfaces in the backcountry - and I am unsure how this storm snow will bond to that. What I do know is that we have a lot of water, snow, and wind on tap for the next few days. The avalanche danger is going to rise, the storm snow will be unstable, and we are going to see avalanches within the new snow. The uncertainty is how long it will take to stabilize and how it will react with the old surfaces. While we have this much uncertainty, it would be a good time to adjust the overall mindset to stepping back, see how the new snow reacts, and with time we can eliminate some of those variables of uncertainty.

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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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