Avalanche Advisory
Advisory: Provo Area Mountains Issued by Evelyn Lees for Tuesday - January 23, 2018 - 7:14am
bottom line

The Avalanche Danger is MODERATE on steep, mid and upper elevation slopes facing northerly through easterly. Human triggered avalanches are possible, and large avalanches can be triggered in isolated places. Avoid the steep, north through easterly facing slopes, where it’s most likely to trigger a slab avalanche.

Periods of winds have created a MODERATE danger for triggering wind drifts along mid and upper elevation ridgelines, which will become more widespread this afternoon. Both dry and wet loose sluffs are possible on steep slopes.
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current conditions

About 4 to 8 inches of settled powder continues to provide slightly improved turning and riding conditions at the mid to upper elevations of the Provo area mountains, though access though the low elevations is still very difficult. This morning, under partly cloudy skies, temperatures are in the teens and the westerly winds are light. Speeds are averaging 5 to 10 mph at the low and mid elevations, and perhaps 10 to 20 mph across the higher peaks.

recent activity

There were reports of a few small sluffs and new wind slabs in the backcountry yesterday, and resort artillery in the Cottonwoods pried out one deep slide on an upper elevation, northwesterly facing slope that broke out near the ground, 150’ wide.

Slightly stronger winds across Cutler Ridge in the Ogden area mountains quickly whipped up some very sensitive wind drifts, foreshadowing the tomorrow’s conditions. Doug Wewer photo
Avalanche Problem 1
type aspect/elevation characteristics
LIKELIHOOD
LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
over the next 12 hours
description

Poor structure – a slab above various layers of weak snow - remains widespread in the snow pack. It is still possible for a person to trigger a slide failing on one of these unpredictable weak, sugary layers, on a steep, shady northwest through easterly facing slope, that would be 1 to 3 feet deep, and up to a couple hundred feet wide. Thinner snowpack areas are particularly suspect – such as rocky rollovers, the Park City and Millcreek ridge lines and drainages and the mid elevations. Weak basal facets have been noted on southwesterly facing slopes, too.

Craig and Andrew went and looked at the Caribou slide in Snake Creek, which failed on one of the facet layers:

Full observation with video here.
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

Vast amounts of snow are available for transport, and a mini wind event yesterday on Cutler Ridge, Ben Lomond, quickly whipped up some very sensitive wind drifts, which could be triggered from a distance. A brief overnight increase in wind speeds created new drifts along the higher elevations, and drifts will become even more widespread as wind speeds increase this afternoon and tonight.

Heads up: tomorrow the landscape and danger will change with strong winds in the forecast.

Cutler ridge wind slab, Doug Wewer photo.
Avalanche Problem 3
type aspect/elevation characteristics
LIKELIHOOD
LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
over the next 12 hours
description

Both dry and wet loose sluffs are possible today.

Dry loose sluffs: could still be triggered today on very steep slopes of all aspects, and a few may be far running if they have slick sun or wind crusts beneath them.

Wet Loose Sluffs: direct sun and warming temperatures this afternoon may dampen the snow surface on south through westerly facing slopes, making it possible to trigger damp sluffs on steep slopes
weather

One more quiet weather day before the winds ramp up tonight and tomorrow ahead of the next storm, on Thursday. Partly cloudy skies this morning will give way to sunny skies this afternoon, with temperatures warming into the upper twenties. Winds should finally settle on a southwesterly direction, and slowly increase, reaching 15 mph averages by afternoon, with gusts in the 20s. The highest ridgelines will reach averages in the 20s, gusting in the 30s. Warm, and increasingly windy tomorrow ahead of Thursday evening’s quick moving storm, which should bring 3 to 5” of new snow
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.