Avalanche Advisory
Advisory: Salt Lake Area Mountains Issued by Drew Hardesty for Wednesday - March 14, 2018 - 5:51am
bottom line

I expect the danger to rise to CONSIDERABLE for wet slab and wet loose avalanches today. They may be most problematic on easterly (NE>SE) and westerly (NW>SW) aspects at the mid-elevations. The danger may be more pronounced along the periphery of the Cottonwoods and more evident in Ogden and Provo. Note that wet avalanches may now include mid-elevation northerly slopes with today's warmth and high rain/snow line.

A MODERATE DANGER exists for human triggered slides 2 to 5 feet deep in isolated areas on predominantly (but not limited to) northeast to southeast facing slopes at the mid and upper elevations. Localized pockets of shallow but perhaps sensitive wind drifts may be found along the higher elevations.

Cornices, Glide Releases, and Roof-avalanches are also significant hazards to have on the radar today.




special announcement

Alta will not be closing Grizzly Gulch in support of avalanche mitigation efforts on Patsy Marley for today.


How does an avalanche accident happen? What is it like to be caught? What can we learn? Read a first-hand account of the avalanche accident in the Meadow Chutes that happened on January 26th. The full accident report can be found here.

A write-up of an avalanche involvement on Monday in the Little Pine couloir above LCC can be found here.


Join Mark Staples and Drew Hardesty on Monday, March 19 at 7PM for an interactive discussion of the current Wasatch snowpack conditions, a recap of some of the season's accidents, how to stay on the right side of the fracture line in our unusually weak snowpack, and their predictions for the rest of the season. The discussion will occur at RockSteady Bodyworks - 4689 Holladay Blvd Suite E in Holladay.


We couldn't get out on the snow without the great support from Polaris, Ski Doo, and Arctic Cat as well as KTM and Timbersled. Our local dealers make it happen. Tri-City Performance, Weller Recreation, Northstar's Ultimate Outdoors, Big Pine and Morgan Valley Polaris. We use these machines to monitor the snowpack across the state of Utah. We also use these machines to teach life-saving classes.

current conditions

I'm not into it. I don't like the 'overnight low temperatures', the higher humidities, and whatever cloud cover that may have drifted across the range. Overnight lows for many mid and upper elevations are in the upper 30s to low 40s. Winds on the leading edge of the storm are southerly, blowing 30-35mph with gusts to 50. Patches of nice, soft settled powder were reported from yesterday - but I know these people, you can't trust them, they're just happy to be out. In any event, whatever superficial refreeze you find out there will be fleeting at best and those "patches" of soft snow will be hammered by wind, warmth, and light rain to 9000' today.

Note the poor refreeze in the "thermal belt" elevations of Mill D North (8900') of BCC and Lookout of the northern end of the PC ridgeline (8300') below. No bueno.

recent activity

More wet loose activity noted out of the steep south facing couloirs above LCC and in Stairs Gulch of BCC. Control efforts in mid-LCC triggered another avalanche into older faceted snow from the mid-snowpack on an upper elevation east to northeast facing slope.

Avalanche Problem 1
type aspect/elevation characteristics
LIKELIHOOD
LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
over the next 24 hours
description

I don't like the current conditions. I am most concerned about wet slab avalanches today, particularly on steep terrain with an easterly (NE>SE) and westerly (NW>SW) component. These may be even more prevalent along the periphery of the upper Cottonwoods. I am adding wet loose avalanches for the locator rose. Note that wet loose may now include mid-elevation northerly facing slopes with today's high rain/snow line.

Why? Previously scorching daytime highs, poor-at-best overnight refreezes, and forecast light rain up to 9000' today. Melt-water percolating through areas of isothermal snowpack will tend to pool along structural interfaces. A little is fine, too much is not. Dangerous wet avalanches are likely to run naturally and with provocation today.

As a consolation, the riding conditions will be poor: High Risk Low Reward. For more info on Wet Slabs, click on the 'i' next to the Wet Slab icon above.


Cornices are increasingly sensitive and often break back further than expected. Give them a wide berth and avoid travel below them. They may also - if large enough - be enough of a trigger to pry out deeper avalanches below.

Roof-avalanches: Buildings are starting to shed their winter snow, so look up and avoid travel below steep roofs.

Glide avalanches may start to shed in their natural habitat of Stairs Gulch, Broads Fork, and Mill B South of Big Cottonwood Canyon.

Avalanche Problem 2
type aspect/elevation characteristics
LIKELIHOOD
LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
over the next 24 hours
description

We've seen a few close calls with skiers and snowmobilers triggering very large avalanches up to 5' deep in recent days. They are occurring in predominantly (but not limited to) northeast to southeast facing slopes in the mid and upper elevations in steep thin rocky terrain or in more heavily wind loaded areas along the periphery of the Cottonwoods. Suspect layering includes the early February faceted layers and the depth hoar at the ground. These for the most part are unsurvivable.

Yes, it's challenging to see so many suspect slopes nearly hammered with tracks.

Deep slabs don't often offer immediate feedback, but when they do, you'll know it.


A quick list of recent deep slab avalanches can be found below.

03/11/2018 Salt Lake region: Avalanche: Guardsman Pass area, Snowmobiler trigger - 5' deep - 350' wide

03/10/2018 Salt Lake region: Avalanche: First Cornice, Snowmobiler trigger

03/8/2018 Salt Lake region: Avalanche: Hogum, Natural trigger - 5' deep - 300' wide

03/8/2018 Salt Lake region: Accident: Kessler Peak, Skier trigger - 4' deep - 600' wide

03/8/2018 Salt Lake region: Avalanche: Mary Ellen, Explosive trigger - 4' deep - 1/4 mile' wide

weather

A lot going on with the weather picture through the weekend. Big picture - a large scale Pacific weather system will bring wind, precipitation, and cooler temps through Sunday. For today, the HRRR advertises some earlier precipitation (up to 9000' or so) particularly along the Logan and Ogden areas with some light precipitation in the central and south. Lightning may be possible with graupel and additional snowfall this afternoon and overnight. By tomorrow afternoon, many areas (especially the PC, Brighton, Provo, and Ogden areas) may see a dense 6-12" of snow. Winds today will be moderate to strong from the south and southwest. Temps will gradually decrease overnight with ridgetop temps in the mid-teens by tomorrow afternoon. A bit of a break Friday with another piece of the storm Friday night into Sunday morning with more snowfall and even colder temps.

For a great perspective on this winter's snowpack and what may lie in store, check out Jim Steenburgh's recent post Intricacies of This Winters Warmth, Snowfall, and Snowpack

general announcements

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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.