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Forecast for the Salt Lake Area Mountains

Brett Kobernik
Issued by Brett Kobernik for
Tuesday, December 11, 2012

Overall, most areas have a MODERATE avalanche danger today. However, there is a CONSIDERABLE danger on steep easterly facing slopes that could produce quite dangerous avalanches. If you are not able to POSITIVELY identify whether a slope contains buried rain crusts with weak snow and a recent wind load, it’s best to avoid those slopes today. Carefully check the sensitivity of the new snow in the upper Little Cottonwood periphery.

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Weather and Snow

Most areas picked up 2-4 inches of snow in the last 24 hours but upper Little Cottonwood is up to about 10 inches with an inch of water. Winds have tapered off a little bit since yesterday but are still in the moderate speed range from the west or northwest. Temperatures are in the mid teens along the ridges.

Recent Avalanches

Hardesty and I were able to trigger a significant slab avalanche while doing fieldwork on Tuesday. From a safe location and with no one around, we tickled a very small cornice which released a small fresh wind slab. As it gained a little momentum it initiated a collapse failure in weak snow just under the rain crusts from December 4th and 5th. It was around 250’ wide and 1 to 2’ deep. It did not break into the faceted snow from November. This was the same weak layer as the avalanche reported by Ev from Reynolds the day before. We also visited two recent avalanches on Square Top which appear to have similar characteristics. What these all had in common were east to northeast aspects, 9500’ starting zones, weak snow adjacent to buried rain crusts, and a new wind load.

While this is a distinct pattern, it seems like it’s still spotty. The Park City area ski resorts did avalanche control work in non-skier compacted terrain yesterday with no significant results.

A number of people noted that the freshly drifted snow was quite sensitive producing cracking and some small soft slabs. This in itself is a manageable situation as it’s predictable. Something breaking into deeper weak layers is not as predictable and un-manageable IMHO.

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Avalanche Problem #1
New Snow
Type
Location
Likelihood
Size
Description

The biggest threat today is an avalanche that breaks into these deeper weak layers. The most suspect areas are east and northeast aspects between 8500 and 9500 feet where the rain crusts are present and a fresh wind load is also present. These rain crusts are not present once you are approaching 10,000’. This concern seems greater outside of the upper Little Cottonwood periphery although I would still be paying close attention anywhere I travel. Persistent weak layers scare me more than any other type of instability.

Avalanche Problem #2
Persistent Weak Layer
Type
Location
Likelihood
Size
Description

The fresh wind drifts from yesterday will be more stubborn today but don’t disregard them. Slope cuts, small cornice drops and jumping on test slopes should reveal how sensitive they are today. This issue may be more of a concern around the upper Little Cottonwood periphery as this area received the most snow in the last 24 hours.

Additional Information

We should see the skies clearing a bit as the day goes on and ridgetop temperatures should warm into the 20s. West and northwest winds will remain in the moderate category along the ridges. It looks like we have a few chances for snow again in a few days and into early next week as well.

General Announcements

If you trigger an avalanche in the backcountry - especially if you are adjacent to a ski area – please call the following teams to alert them to the slide and whether anyone is missing or not. Rescue teams can be exposed to significant hazard when responding to avalanches, and do not want to do so when unneeded. Thanks.

Salt Lake and Park City – Alta Central (801-742-2033), Canyons Resort Dispatch (435-615-3322)

Ogden – Snowbasin Patrol Dispatch (801-620-1017)

Provo – Sundance Patrol Dispatch (801-223-4150)

Dawn Patrol Forecast Hotline, updated by 05:30: 888-999-4019 option 8.

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Remember your information can save lives. If you see anything we should know about, please participate in the creation of our own community avalanche advisory by submitting snow and avalanche conditions. You can also call us at 801-524-5304 or 800-662-4140, or email by clicking HERE

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This advisory is produced by the U.S. Forest Service, which is solely responsible for its content. It describes only general avalanche conditions and local variations always exist. Specific terrain and route finding decisions should always be based on skills learned in a field-based avalanche class.

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