Salt Lake Avalanche Advisory

Forecaster: Evelyn Lees

AVALANCHE WATCH »

The risk of an avalanche is expected to increase significantly but the timing and location are still uncertain. Stay tuned for updates.
Notice:

The Avalanche Watch has been continued for the mountains of northern and central Utah. Heavy wet snow and rain falling on a weak snowpack is creating dangerous avalanche conditions. The avalanche danger will continue to rise all weekend and through early next week. Backcountry travelers should avoid steep slopes and avalanche runout zones.

BOTTOM LINE

Danger by aspect and elevation on slopes approaching 35° or steeper.
(click HERE for tomorrow's danger rating)


Danger Rose Tutorial

The avalanche danger will rise rapidly today to LEVEL 3 (CONSIDERABLE) on any steep, wind drifted slope and on steep slopes that receive about 8 or more inches of snow. The danger will also rise to LEVEL 3 (CONSIDERABLE) any time you are in a place where the snow changes to rain. LEVEL 3 means natural avalanches are possible, and human triggered slides likely. On low to moderate angled slopes, and out of the wind and rain affected terrain, the avalanche danger is LEVEL 2 (MODERATE). Backcountry travelers today need good route finding and avalanche skills, and should constantly reevaluate the increasing avalanche danger, especially during periods of heavy snowfall or if the winds increase where you are.

CURRENT CONDITIONS

A warming, southwest flow is bringing light snow to the mountains this morning. As of 6 am, the Provo and Ogden area mountains have received 4 to 8” of dense snow, with the Cottonwoods and Park City side in the 1 to 4” range. Temperatures have warmed steadily over the past 24 hours, and are now in the upper teens to mid 20’s. The southerly winds are averaging 10 to 20 mph, with gusts to 30 across the highest terrain.

RECENT ACTIVITY

There were late day reports of easily triggered, very shallow wind slabs, due to the increase in afternoon wind speeds. Sluffs continued to be easy to trigger on steep slopes.

THREAT #1
WHERE PROBABILITY SIZE TREND
      Over the next 24 hours.

The weak layer is in place – and here comes the slab!

Very weak surface snow in the form of near surface facets and surface hoar covered the snow surface yesterday. This weak layer is unusually wide spread, and can be found on almost all aspects and elevations. It is being covered with a layer of increasingly dense new snow, and by afternoon the weak layer could be buried anywhere from 6 to 12 inches deep in the Salt Lake, park City and Ogden mountains (and up to 10 to 16” deep in the Provo area mountains). This weak layer/slab combination will be:

· Very sensitive, and easy to trigger on steep slopes, especially wind drifts

· Slides may be triggered remotely from a distance

· On steep south through west facing slopes, the weak snow is underlain by a very slick melt freeze crust, so once the snow gets moving, it could entrain, or pick up, additional snow, making for longer running slides with a deeper debris pile.

· Be aware of what is above you, and avoid travel below steep slopes

Days of increasing avalanche danger are often tricky and when accidents happen - so constantly reevaluate the changing avalanche conditions.

With numerous great observers sticking their noses into the snowpack, there is one thing we know about the much talked about rime crust –is how variable it is in thickness, location by aspect, elevation and drainage and strength of the facets below it. I expect in some place will become a player, possibly later today, but most likely Sunday into Monday, as the snow piles up.

THREAT #2
WHERE PROBABILITY SIZE TREND
      Over the next 24 hours.

Warming temperatures will change the snow to rain as the day goes on, with rain falling as high as 7,000’. As rain falls on the on new snow, the avalanche danger will rise rapidly, and wet loose sluffs and shallow slabs could become easy to trigger or even run naturally. Especially avoid travel in terrain traps such as gullies, creek beds and below steep road banks, where even a small slide can pile up deeply.

MOUNTAIN WEATHER

A very moist southwesterly flow will bring several rounds of snow this weekend into early next week. Snow today, with areas favored by southwest flow (including the Provo and Ogden area mountains and upper Big Cottonwood Canyon) receiving 6 to 10” of additional snow. Additional snow in other areas will be in the 3 to 6” range. Temperatures will warm throughout the day, to around freezing at 8,000’ and into the mid 20’s at 10,000’. The snow/rain line could rise to about 7,000’ today. Snow will taper off this afternoon, with 2 to 5” expected tonight. Another round of heavier snowfall is expected Sunday afternoon through Sunday night.

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 – Alta Central (801-742-2033)

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

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

Discount Lift tickets: Ski Utah, Backcountry.com, Alta, Deer Valley, Park City, The Canyons, Wolf Mountain, Snowbasin, Beaver Mountain, Brighton, Sundance, and Solitude have donated a limited number of tickets for sale.

Wasatch Powderbird Guides flight plan. Today, WPG may be flying the Daisy Bell avalanche mitigation device in and around Alta. In addition WPG may do limited non commercial training and reconnaissance throughout our entire permit area. WPG opening day for the 2011 season is Wednesday December 15.

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

Daily observations are frequently posted by 10 pm each evening.

Subscribe to the daily avalanche advisory e-mail click HERE.

UDOT canyon closures UDOT at (801) 975-4838

You have the opportunity to participate in the creation of our own community avalanche advisory by submitting avalanche and snow observations. You can also call us at 801-524-5304 or 800-662-4140, or email to uac@utahavalanchecenter.org

Donate to your favorite non-profit – The Friends of the Utah Avalanche Center. The UAC depends on contributions from users like you to support our work.

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.

We will update this forecast tomorrow morning. Thanks for calling.

This information does not apply to developed ski areas or highways where avalanche control is normally done.  This advisory is from the U.S.D.A. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur.

This advisory provided by the USDA Forest Service, in partnership with:

The Friends of the Utah Avalanche Center, Utah Division of State Parks and Recreation, Utah Division of Emergency Management, Salt Lake County, Salt Lake Unified Fire Authority and the friends of the La Sal Avalanche Center. See our Sponsors Page for a complete list.