Avalanche forecast

Ogden

Issued Dec 20, 2020valid to Dec 21, 2020Utah Avalanche Center

Avalanche danger

Alpine
Treeline
Below treeline

Out of date — this forecast expired 6 years ago. You’re viewing past conditions, not the current bulletin.

Highlights

Human triggered avalanches remain likely at the west through north through southeast facing upper elevation slopes where the weak faceted snow combined with fresh wind drifts are the main avalanches problems. In these places the avalanche danger is CONSIDERABLE. Stay off of and out from underneath slopes 30° degrees and steeper at the mid and upper elevations. If you trigger an avalanche, it is likely to break down 18-30" and up to several hundred feet wide. South facing upper elevations and mid elevations generally had less wind and snow, but human triggered avalanches definitely remain possible, and the avalanche danger is MODERATE.

At low elevations, the snow fell on bare ground, and the avalanche danger is LOW.

Avalanche problems

Persistent Slabs
N
NE
E
SE
S
SW
W
NW
Alpine
Treeline
Below treeline
Likelihood
Very Likely
Size
3
Over the last two days many human triggered and natural avalanches were observed in the Central Wasatch, which has a similar snowpack. Most of these avalanches were triggered remotely, failing on the weak faceted snow and some were quite large, up to 2' deep and a few hundred feet wide.

Weak faceted snow from storms in early and mid-November makes up the base of our snowpack on most aspects at the mid and upper elevations. This layer will eventually begin to gain strength and heal; however, over the past few days, we quickly added around a foot of snow (or more), an inch of water, and continue to add strong winds at the mid and upper elevations. With this much weight and stress on this layer, as well as obvious signs of weakness like avalanches, this layer will not be trusted for the foreseeable future.

In this video Greg talks about the current snowpack in the Ogden area, find his full James Peak observation HERE.

Today, you are very likely to trigger an avalanche in terrain steeper than 30° that has the persistent weak layer of faceted snow buried underneath the storm snow. These avalanches can be triggered remotely and from below.
Wind Slabs
N
NE
E
SE
S
SW
W
NW
Alpine
Treeline
Below treeline
Likelihood
Likely
Size
2
Over the last two days, the winds have remained strong enough to drift snow, with gusts near 50 mph at the highest of ridgelines. Today these drifts will be most widespread on the south through east-facing slopes, especially at the highest most elevations. However, sustained high winds can deposit snow around terrain features on almost any aspect, called cross-loading. For this reason, I would expect to find sensitive slabs of wind drifted snow at all upper slopes, especially along with terrain features such as ridgelines, sub ridges, and gullies.

Such strong winds today will continue to form both soft and hard slab avalanches in upper elevation wind drifted terrain. As the winds continue to blow, these slabs will become more firm and cohesive. This can allow you to travel out farther onto the slope before it breaks, and can fail larger and wider than expected. Triggering an avalanche that initially fails in the wind-drifted snow will likely break down more deeply into the weak faceted snow below.

Today continue to look for slopes with any signs of wind drifted snow, such as cracking, hollow noises, and pillow-shaped snow and avoiding those slopes.

Photo of drifting snow, an obvious sign of wind loading occurring, from Solider Peak yesterday (PC: M. White)

In areas that have remained sheltered from the elevated winds, you may be able to find sensitive storm slabs up to 1’ deep. Remember, terrain traps like gullies or creeks can cause these shallow slabs to pile up much deeper and could be enough to bury a person.

Snow and Weather

This morning, under partly cloudy skies the temperatures range from the mid-teens to low 20s F. Winds are south southwesterly, and averaging in the teens at mid-elevations and gusting up to 30mph. At upper elevations, the winds are averaging in the 40s and gusting up to 50 mph.

For today, expect mostly cloudy skies as high pressure aloft to the west of Utah today will generate an increasingly strong and moist west-northwest flow across the Wasatch range through this evening. This means an increase in winds at mid and upper elevations, as well as a chance for light snow this afternoon. Winds will be Westerly, averaging 10-20 mph with gusts up to 40 mph. Temperatures will be in the upper 20s to low 30s F.

Week in Review: Our first Week in Review - where we summarize snow and avalanche conditions for the past week - has been published.

Special Avalanche Bulletin

AVALANCHE CONDITIONS REMAIN DANGEROUS FOR THE MOUNTAINS OF NORTHERN AND CENTRAL UTAH, INCLUDING THE WASATCH RANGE...THE WESTERN UINTAS, AND THE BEAR RIVER RANGE. RECENT HEAVY SNOWFALL AND DRIFTING FROM STRONG WINDS HAS CREATED AREAS OF UNSTABLE SNOW. HUMAN TRIGGERED AVALANCHES ARE LIKELY. TRAVEL IN AVALANCHE TERRAIN IS NOT RECOMMENDED. STAY OFF OF AND OUT FROM UNDERNEATH SLOPES STEEPER THAN 30 DEGREES

Special Announcement

Thanks to the generous support of our local resorts, Ski Utah, and Backcountry, discount lift tickets are now available. Support the UAC while you ski at the resorts this season. Tickets are available here.

Recent Activity

No new avalanches have been reported in Ogden. In the Central Wasatch, since Friday there have been twenty six human-triggered or natural avalanches reported. Many of these avalanches were large, up to 400' wide, and triggered remotely (from a distance) failing in weak faceted snow that is now buried 18-30" deep. Overall this, in combination with the widespread cracking and collapsing being observed, is a huge indication of the sensitivity of our weak snowpack structure.

Photo: Mark White, Lower Cardiff Fork near the mine. Triggered remotely from 10 feet away. Even small slopes were sensitive to remote triggers yesterday.

Find a full list of yesterday’s avalanches here.

A video below from Observer Dave Coyne showing widespread, likely natural activity throughout Grizzly Gulch Proper.

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.

Observations and Avalanches

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