Avalanche Advisory
Advisory: Provo Area Mountains Issued by Evelyn Lees for Saturday - February 17, 2018 - 7:41am
bottom line

The avalanche danger is CONSIDERABLE on steep, upper elevation north through easterly facing slopes with recent deposits of wind-drifted snow. A triggered wind drift may step down to a deeper weak layer, resulting in a large, dangerous avalanche. Most other steep mid and upper elevation terrain has a MODERATE avalanche danger.

Low angle, wind sheltered, shady slopes will have the best powder snow with less avalanche risk.

Sunday and Monday - a winter storm with strong winds and heavy snowfall will increase the avalanche danger in all the mountains of northern and central Utah. Local avalanche forecasts are updated every morning.
special announcement

We are saddened to report that Orem resident Alexander Marra was killed in an avalanche today, Saturday, February 10, in Wyoming. He was skiing out-of-bounds at JHMR, and triggered a 2-foot deep slide that took him over cliffs. Our thoughts and sympathies go out to his family and friends. Accident Report.

Episode 5 of the UAC podcast "To Hell in a Heartbeat - A Conversation With Tom Diegel and Matt Clevenger About the 12.26.08 Full Burial on Little Water" is live. Matt and Tom about the avalanche documented in To Hell in a Heartbeat. Check it out on ITunes, Stitcher, the UAC blog.
current conditions

After 48 hours of well-behaved winds, speeds kicked up last night, especially at the upper elevations. At times, the southwesterly winds have averaged 25 to 30 mph at the mid elevations in the Provo area mountains, with gusts in the 40s. The upper elevations are where the real action is – just to the north, 35 to 45 mph averages, gusting to 60 mph. Mountain temperatures range from the teens to the low twenties.
recent activity

Thanks to an observation from Woody: Two slides observed in Cascade Cirque on apron below main head wall. The larger one is on an ENE face at 10300' and appears to be 600' wide by 12" deep. The second is on a NE shoulder at 10000' and appears to be roughly 200' wide by 12" deep. Can't tell if they are hard slabs or soft slabs. Best guess is that they ran naturally yesterday mid-day sometime. 11000' ridge tops had significant wind transport onto the E-NE faces today. (Looked like snow guns were set up and blowing along the ridge line of Timp today

It's been very active to the north in the Salt Lake and Park City area mountains:

With better visibility, we have more information on avalanches from both Thursday and Friday:

02/16/2018 Salt Lake region: Avalanche: West Monitor, Snowboarder trigger - 2' deep - 350' wide

02/16/2018 Salt Lake region: Avalanche: Little Superior, Skier trigger - 14" deep - 40' wide

02/15/2018 Salt Lake region: Avalanche: Cardiff Fork, Natural trigger - 40' wide

02/15/2018 Salt Lake region: Avalanche: Emma Ridges, Skier trigger - 18" deep - 20' wide

02/15/2018 Salt Lake region: Avalanche: Reynolds East Face, Skier trigger - 3' deep - 50' wide

02/15/2018 Salt Lake region: Avalanche: Catchers Mit, Skier trigger - 2' deep - 100' wide

02/15/2018 Salt Lake region: Avalanche: Pointy Peak, Natural trigger - 2' deep - 100' wide

02/15/2018 Salt Lake region: Avalanche: Airplane Peak, Natural trigger - 3.5' deep - 100' wide

02/15/2018 Salt Lake region: Avalanche: Hogum Hogback, Natural trigger - 2' deep - 70' wide
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

Today’s stronger winds have lots of snow to drift and blow around. Wind drifts, known as wind slabs, often look smooth and rounded, and when you find one, they can be cracky, denser and deeper than the surrounding snow. As the winds are getting well down into the mid elevations, look for drifts along both mid and upper elevation ridge lines and cross-loaded along gully walls, mid slope break overs and sub ridges. Avoid any wind drifts on steep slopes. The winds are significantly stronger at the upper elevations, so be aware of steep wind drifted slopes above – natural avalanches are possible.

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

The weight of Thursday’s snow was enough to make the buried faceted weak layers reactive once again on a few slopes. Today’s westerly winds will be adding more snow and weight onto slopes with buried facets – especially upper elevation slopes facing northerly through easterly, making them easier to trigger. A wind slab avalanche could trigger a deeper slide, failing on one of these faceted weak layers.

There is a lot of variability in the snowpack strength and depth, with facet layers both mid pack and near the ground. Slopes with a shallower snowpack tend to have weaker snow – including slopes that have slid one or more times this year. Cracking and collapsing are bulls-eye clues to instability.

Avalanche Problem 3
type aspect/elevation characteristics
LIKELIHOOD
LIKELY
UNLIKELY
SIZE
LARGE
SMALL
TREND
INCREASING DANGER
SAME
DECREASING DANGER
over the next 10 hours
description

Even with the cooling breeze, sun and warm temperatures may heat the snow on steeper southeast through westerly facing slopes today. Human triggered and natural wet loose sluffs will become possible as the snow becomes damp and wet, possibly running longer than expected on the slick crusts beneath. Roller balls are often the first sign on heating snow.
weather

It will be warm and windy today, with temperatures nearing 30 at 10,000’ and 40 to 45 at 8,500’. Winds will increase with elevation – 20 to 30 mph averages at 9 to 10,000’, with gusts in the 40s. The highest peaks will average to 40 mph, with gusts in the 60s.

It will be very windy tonight and Sunday ahead of a strong cold front that should reach northern Utah late Sunday afternoon, bringing periods of snow through at least Monday night. 12 to 24” are possible.
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.