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Forecast for the Salt Lake Area Mountains

Drew Hardesty
Issued by Drew Hardesty for
Wednesday, December 19, 2012

Conditions remain dangerous in the backcountry. Areas of CONSIDERABLE danger exist in the mid to upper elevation northerly through easterly facing terrain. Human triggered slides 2-4' deep are possible...and they may be unsurvivable. Remotely triggered slides remain possible as well. Collapsing/whoomphing confirms the instability. Lack of same does little to deny it. You can find excellent and safe powder on mid-elevation slopes gentler than 30 degrees.

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Special Announcements

Discount lift tickets are in! With a wild week of weather and backcountry avalanches in the forecast, heading to one of our world class resorts is a great idea. Go to http://www.backcountry.com/utah-avalanche-center to get tickets from our partners at Beaver Mountain, Brighton, Canyons, Deer Valley, Park City, Powder Mountain, Snowbasin, Snowbird, Solitude, Sundance, and Wolf Mountain. All proceeds benefit the Utah Avalanche Center. A big thanks to the Utah mountain resorts - we couldn't do it without your partnership.

There are 3 free awareness events this week - a talk and webinar at White Pine Touring in Park City and Know Before You Go talks at Scheels in Sandy and Kirkhams in SLC. The first of a series of Thursday night presentations at Snowbird will be held this week, with Tyson Bradley of Utah Mountain Adventures presenting a 2012 Haute Route trip.
Details on this event and more at http://utahavalanchecenter.org/events/calendar/month

Weather and Snow

WOW! It's been a wild week of storms - 2-3' of storm snow (more on this later), Monday's chair-lift halting winds, an additional 6-12" Monday night...and now sub-zero temps. Skiing and riding conditions are 5 star. Out of 5.

Skies are clear. Since midnight the northwest winds have bumped to 15-20mph with gusts to 30 and temps are in the deep freeze. Did I mention the riding conditions?

Recent Avalanches

Looks like nearly each mountain resort had at least one explosive triggered avalanche that stepped a few feet down into old faceted snow. These were on steep northwesterly through easterly facing slopes at the upper elevations. Otherwise, most of the slides were within the recent storm snow. In the backcountry, we did hear about a snowboarder along the northern Brighton periphery that triggered - and escaped - a 3' deep and 80' wide wind slab there on a steep northeast facing slope at roughly 10,200'.

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Avalanche Problem #1
New Snow
Type
Location
Likelihood
Size
Description

Let's take a closer look these persistent slabs. The "monsters in the basement" (or at least on the 2nd floor) formed Nov 30th through the first week of December with 3-4 rain events up to give-or-take 9500'. Weak sugar faceted snow developed along these crusts...but it must be noted that "spatial variability" here is as dramatic as I've seen. Since then, we've had plenty of snow and blow...but remarkably few - about a dozen - avalanches in the backcountry. (It should be noted that these are reported slides...and I would imagine that with good visibility today people will spot some others in steep terrain that ran on Monday/Tuesday).

A rough tally of snow/snow-water-equivalent - that is - the thump - or load on these weaknesses - is as follows since the last rain event on the 5th:

Ogden mountains - 18"/1.56"

Park City mountains - 33"/2.14"

Cottonwoods (very rough) - 64"/4.18"

Provo mountains - 48"/4.72"

And let's not forget Monday's strong west to southwesterly winds, averaging 30-50mph with some gusts to 80.

These persistent slabs are now generally buried 18-36" deep across the Wasatch...and I suspect they will continue to be problematic for the next few days, if not more. A poor snowpack structure -as described - with a significant load - as described - should be treated as suspect. To me they are particularly dangerous because they are covered now by 5 star powder and stubborn wind drifts. They are also inconsistently at best, dangerously at worst - reactive to ski and slope cuts and cornice drops. Clear skies, excellent powder, and slowly dropping hazard with a persistent weak layer has long been a tragic combination.

The take home point is to come home at the end of the day. If in doubt, follow this guy's lead and choose gentler terrain with nothing above.

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

The increase in wind speeds from the north-northwest overnight will have some shallow manageable drifts relegated to the higher elevation easterly through southerly terrain. The rose represents the older wind slabs from Monday as well.

Avalanche Problem #3
Cornice
Type
Location
Likelihood
Size
Description

Yawning cornices drape many of the exposed ridgelines and will break back further than expected. A ride over with the boxcar may then trigger a larger, deeper avalanche.

Additional Information

Building high pressure will bring clearing skies, light to moderate winds, and warming temperatures over the next few days. Today we'll have temps in the single digits, and west to northwest winds blowing 15-20mph. The ridge breaks down over the weekend ahead of what looks like a return to an active storm pattern...starting Sunday. Stay tuned.

General Announcements

Go to http://www.backcountry.com/utah-avalanche-center to get tickets from our partners at Ala, Beaver Mountain, Brighton, Canyons, Deer Valley, Park City, Powder Mountain, Snowbasin, Snowbird, Solitude, Sundance, and Wolf Mountain. All proceeds benefit the Utah Avalanche Center.

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)

Powder Mountain Ski Patrol Dispatch (801-745-3773 ex 123)

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

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

Twitter Updates for your mobile phone - DETAILS

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

Wasatch Powderbird Guides does daily updates about where they'll be operating on this blog http://powderbird.blogspot.com/ .

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 bysubmitting snow and avalanche conditions. You can also call us at 801-524-5304 or 800-662-4140, or email by clicking HERE

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.

For a print version of this advisory click HERE.

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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