Wasatch Cache National Forest

In partnership with: The Friends of the Utah Avalanche Forecast Center, Utah Department of Public Safety Division of Comprehensive Emergency Management, Salt Lake County, and Utah State Parks

The Utah Avalanche Center Home page is: http://www.avalanche.org/~uac/

Avalanche advisory

Saturday, December 28, 2002

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Good Morning. This is Evelyn Lees with the Forest Service Utah Avalanche Center with your backcountry avalanche and mountain weather advisory. Today is Saturday, December 28, 2002, and it’s 7:30 in the morning.

Current Conditions:

The mountain temperatures have continued to warm, and are in the mid twenties to near 30 at most stations. The southerly winds are increasing. Currently, they are averaging 15 to 25 mph along the higher ridges, with gusts 35 to 45. Late yesterday, the southwesterly winds were stronger for several hours, averaging 25 to 35 mph with gusts in the 40’s and 50’s. The warmer temperatures and widespread wind damage have created tricky turning and riding conditions on all but the most sheltered shady slopes.

Avalanche Conditions:

Yesterday, the combination of warming temperatures and a few hours of moderate winds created an impressive increase in avalanche activity.

Numerous natural avalanches occurred. There were two along the Park City ridgeline that were southeast facing, about 8 to 14” deep, 100’ wide and broke into old snow. Another southeasterly facing natural slide was reported from upper Dry Fork, at about 10,400’, that was about 2 feet deep and 80’ wide. In the Ogden area mountains there was a natural hard slab, that was 2-4’ deep hard and 100’ wide, that broke in older snow and to the ground in places. There were also several smaller fresh wind slabs that broke out spontaneously on northeasterly facing slopes in the Mill Creek drainage and in the Ogden area mountains. These new wind slabs are failing on weak surface snow that includes surface hoar in some locations.

There were 4 human triggered slides in the Ogden area mountains, including two on slope angles of about 30 degrees or less. All of these were on northeasterly facing slopes, below 8,600’. In the Salt Lake mountains, a group was carefully working a ridge above Main Days, when the third person triggered a slide. It was 100’ wide, 1 ½ to 2’ deep, and ran on the loose facets near the ground.

And finally, resorts in both the Ogden area mountains and the Salt Lake mountains got deep hard slabs from control work yesterday. They were two to four feet deep, 100 to 200’ wide, and running on surface hoar or near the ground on depth hoar.

So once again, the avalanche danger is on the rise. The major avalanche problem today will be fresh drifts of wind blown snow. In addition to being along the ridges, the sensitive winds drifts will be well off the ridges on both mid and lower elevation slopes, and could break out 1 to 2’ deep. Expect the most widespread drifts on northerly through easterly facing slopes. But the strong winds will also drift snow onto other aspects, especially around sub ridges, gully walls, and steep breakovers. These wind drifts will become more widespread as the day goes on. It will also be possible to trigger one of the deeper hard slabs running on old snow. Many of the slopes that avalanched last week could go again early in this storm cycle.

If you choose to travel in the backcountry today, use great caution. Stick to low angle slopes, of about 30 degrees or less, and seek wind sheltered areas. Realize it is a day of rising avalanche danger, and conditions may change rapidly. Many of the ice climbs in the northern Utah mountains are in avalanche paths. With the combination of warming temperatures and the possibility of natural avalanche activity today, ice climbers need to consider the avalanche danger.

Bottom Line (SLC, Park City, Ogden and Provo Area Mountains):

The avalanche danger is HIGH today on northwest through northeast through southeast facing slopes of about 35 degrees or steeper and on any steep slope with recent wind drifts, above about 8,000’. Both natural and human triggered slides are likely. The danger is lower on slopes of about 33 degrees or less and in wind sheltered areas.

Mountain Weather:

A cold Pacific trough will arrive in Utah early on Sunday. Ahead of the trough, we can expect mostly cloudy skies today and rapidly increasing southwest winds. The winds should be nuking by mid day, with ridge top averages reaching sustained speeds of 35-50 mph, with gusts over 60 mph. The warming trend will continue, with highs today in the mid 40’s at 8,000’ and low 30’s at 10,000’. Tonight, the very strong southwest winds will continue, with lows in the mid to upper twenties. Snowfall should begin by dawn, and continue into Sunday night. Snow totals should be generally a foot by Monday morning, with locally higher amounts.

General Information:

Wasatch Powderbird Guides will not be flying today.

The Friends of the Utah Avalanche Center will offer an intensive 3-day avalanche class January 18-20. You can sign up at the Black Diamond Retail Store or call them at 801-278-0233.

To report backcountry snow and avalanche conditions, especially if you observe or trigger an avalanche, call (801) 524-5304 or 1-800-662-4140, or email to [email protected] or fax to 801-524-6301. The information in this advisory is from the U.S. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur.

I will update this advisory by 7:30 on Sunday morning.

Thanks for calling!

________________________________________________________________________

National Weather Service - Salt Lake City - Snow.

For an explanation of avalanche danger ratings:

http://www.avalanche.org/usdanger.htm