Avalanche Advisory
Advisory: Salt Lake Area Mountains Issued by Evelyn Lees for Wednesday - February 28, 2018 - 6:25am
bottom line

The avalanche danger is MODERATE on all steep, mid and upper elevation slopes. Wind drifts can be found and triggered around the compass, both along ridge lines and well off the ridges. Deeper slides can be triggered on west through north through southeasterly facing slopes, expecially on slopes with a thinner snowpack.

With the complex snowpack, continue cautious route finding, careful snowpack evaluation and conservative decision making are important.

You will find better and safer skiing and riding conditions on lower-angled wind sheltered slopes, with no steep slopes above.
special announcement

The Whole Foods Bag Donation to support the UAC has been extended to March 31. When you bring your own bags to Whole Foods in Sugar House, Trolley Square, and Cottonwood Heights you can choose to have the UAC be the recipient of your 10 cent bag credit.

Spend some time improving your rescue skills or learning about avalanches in this upcoming Salt Lake City area class:
current conditions

Skies are partly cloudy this morning, and some mountain locations received a dusting of snow overnight. Temperatures are in the teens, with a few single digits at the highest elevations. The westerly winds are as quiet as they’ve been lately – averaging 5 to 10 mph, with even the highest peaks only averaging 15 to 20 mph.

While there is wind damage on many aspects and sun crusts on some southerly facing slopes, soft dense powder remains on sheltered, shady slopes.
recent activity

Two small slides were triggered in the Cottonwoods yesterday – a very small hard wind drift at 8600’ on a west facing slope in Mineral Fork and a small slide in lower Main Days, 2 feet deep by 20 feet wide, breaking to the ground in a very shallow snowpack area (most likely a repeater, a slope that has already slid one or more times this year).

Andy Rich photo – small hard wind slab, Mineral Fork
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

Monday’s strong southwesterly winds built pencil hard wind slabs, along ridge lines and scattered down in open bowls and the mid elevations. While they will be more stubborn today, they still can be triggered by a person, and be anywhere from a few inches to two feet deep. Hard slabs are different from the soft wind drifts we’ve been dealing with lately – they almost always break above you, and often on the second or third person.

New hard cornices have grown along ridgelines. Hard cornices break back even further, often onto what looks like flat terrain on the ridge. So give them a wide berth and avoid travel below them.

Left - hard slab diagram – read more about them here. Right - Mark White photo, West Monitor cornice.
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

Variable and unpredictable – how to define our current faceted weak layers that exist in both the mid pack and near the ground. The weakest mid pack layers, averaging 2 feet deep, are near a dirt layer or thin buried crusts. In the shallower snowpack areas, a few slides broke near the ground just two day ago. These were natural avalanches, 2 to 5 feet deep on Mill Canyon peak and in Mineral Fork. These deeper slides can be triggered by a person, smaller slides or cornice falls.

Avoid, steep shallow, rocky, wind loaded terrain, where the snowpack is thinner and more suspect. If you trigger a persistent slab avalanche it will likely be unsurvivable. Cracking and collapsing are bulls-eye clues to instability, but these clues may not be present, and snow pit tests could be unreliable.

Photo: Peter Vintoniv - Feb 26th Mineral Fork. This photo is one of three avalanches, all failing in faceted (weak) snow near the ground.
weather

Today will be the last calm, quiet day this week. The morning’s clouds should thin rapidly, and skies become partly to mostly sunny. The westerly winds will remain light all day, averaging 5 to 15 mph, with the highest peaks only averaging to 20 mph. Temperatures will warm into the upper teens to mid 20s.

The next storm continues to look good – light snow and increasing winds Thursday, strong winds Friday, with the cold front arriving Friday night, and periods of snow, heavy at times, possible through Sunday.
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.