Salt Lake Avalanche Advisory

Forecaster: Drew Hardesty

SPECIAL ANNOUNCEMENT

Alta will be close to uphill traffic through the rest of the week for avalanche control. The summer road will remain open.

BOTTOM LINE

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


Danger Rose Tutorial

A CONSIDERABLE danger remains in the mid and upper elevation wind drifted terrain. Human triggered soft and hard slabs up to 2’ deep are still possible, particularly in the north through east through southeasterly facing terrain. Mind the warnings of a collapse in the snowpack. Most of the old timers are likely to give it another couple of days. The riding conditions may be just fine on the wind-buffed gentler slopes.

CURRENT CONDITIONS

Skies are clear and the winds, mercifully, are calm. Disappointing that most of our snowpack has blown into the Uinta Basin. Ski Vernal does have a catchy ring to it. But I digress. With the passing of the front yesterday, dark clouds cloaked the range, screaming winds tore through every nook and cranny, and a few inches of graupel fell sideways and upside down. The west to northwesterly freight train blew 40-50mph with gusts pushing 100mph. It wasn’t pretty. Temperatures are now in the low teens. At least the trail-breaking will be easy.

RECENT ACTIVITY

Observers reported cracking and widespread collapsing and no one that I knew or talked to stuck their neck out into the steep terrain. You didn’t have to. Walking the ridges on the southeastern end of the Park City ridgeline, Evelyn remotely triggered two hard slab avalanches, each up to 2’ deep (and sent out the info on Twitter -shameless plug for our Twitter feed – sign up off the home page – or click here). One pulled out 100’ wide and the other 300’ wide, collapsing Sunday’s rime crust and breaking into the lighter density snow beneath. These were on north and easterly slopes at roughly 9800’, breaking just below the ridgelines. Check her report and photos under Current Conditions.

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

Warning! Lots of snowpack musing below....

It’s possible that we went through our first cycle of the season only to have everything immediately filled back in. The winds were that strong and the transport that significant. When you have 2-3” of what we call ‘water weight’ and strong wind, the load will almost always find a weak interface and induce failure within the snowpack. In this case, we now have an interesting scenario…

Here’s the story. Sunday’s rime crust capped an inch or two of low density snow that may or may not have faceted (more on this in a minute). Theoretically anyway, these crusts can often have enough strength to hold an increasingly large load before failing and collapsing onto the ‘air’ or weaker snow beneath. It’s why these crusts and/or hard layers of snow are often referred to as ‘bridges’ – they can allow safe travel above, but when they fail, it can be catastrophic. Stress can be concentrated and most severe at these thin disconnects or interfaces. At this point, it doesn’t matter for today if the snow beneath the crust is faceted or not. The crust failed yesterday, it’ll fail today. But we have to forecast for down the road and understand the extent, pattern or distribution of Sunday’s rime event. During our winter Olympics, we had a January rime event and we wrote ‘Today’s a day to mark on your calendar.’ We had avalanches ripping down to that layer for the next three months.

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

Wind slabs continued...

In the meantime, collapsing should still be evident, though shooting cracks less so. The cornices and wind drifts have become more welded and stubborn and perhaps more dangerous – they may propagate wider than expected, or even behind you. Wind drifted patterns will, of course, be all over the map. Assess each terrain feature separately. The only equalizer will be slope angle, and hard slabs can have the underhanded tendency to pull out onto lower angled slopes.

MOUNTAIN WEATHER

Should be glorious out there today. Warming mountain temperatures and slightly increasing backing winds to the west, however, are setting the stage for the next event. We may even start to see a few high cirrus today or tomorrow. 8000’ and 10,000’ temps will rise into the low 30s and mid-20s, respectively. The weather models agree upon a large scale weather system engulfing the intermountain west from Saturday through mid-week. Looks pretty good.

GENERAL ANNOUNCEMENTS

Please contact Alta Central (801-742-2033) if you trigger a large avalanche in the backcountry - especially if you are adjacent to a ski area - 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.

Soon! 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 at discounted prices.

Wasatch Powderbird Guides flight plan.

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

Daily observations are frequently posted by 10 pm each evening.

Free UAC iPhone app from Canyon Sports.

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

UDOT canyon closures UDOT at (801) 975-4838

We appreciate all your 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.