Avalanche Advisory
Advisory: Provo Area Mountains Issued by Evelyn Lees for Monday - March 26, 2018 - 6:44am
bottom line

The avalanche danger is MODERATE at the mid and upper elevations, especially on the northerly through easterly facing slopes. Shallow wind drifts, sluffs and new snow soft slabs can be triggered on steep slopes. Even a small slide can be serious in radical terrain, and the Provo area mountains have plenty of that.

There remains an isolated chance of triggering a Deep Slab avalanche 2 to 5 feet deep on northerly through easterly facing slopes at the upper elevations. Slopes that are rocky or have a shallower snowpack are most suspect, especially in terrain that has slid one or more times this year.
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current conditions

The cooling trend continues – with wintery temperatures in the teens and single digits this morning in the Provo area mountains. Winds are currently from the northwest and light – averaging less than 10 mph at most stations, and 15 to 20 mph at the 11,000’ level to the north.

Light snow is still falling in the mountains, and the hoped for “refresh” is still in progress…24 hour snow totals are currently 2 to 4” in the Provo area mountains, 1 to 4” in the SLC and PC area mountains and 2 to 8” in the Ogden area mountains. There are supportable crusts beneath the new snow on most aspects and elevations, with upper elevation northerly facing slopes holding the best of the shallow, cold dry snow. The icy crusts will not soften for the next few days, so be prepared for hard, “slide for life” conditions on many aspects in steep terrain.
recent activity

No new avalanches were reported yesterday.

A large avalanches was intentionally triggered Saturday morning by UDOT in Provo Canyon in the Slide Canyon drainage. It started at 10,400 feet as a dry slab avalanche and ran nearly 4000 feet vertical becoming wet as it descended. Recent Provo observations:

03/24/2018 Observation: UFO Bowls Provo region Hardesty, Wilson

03/23/2018 Avalanche: Slide Canyon Provo region Woody

03/22/2018 Avalanche: Cascade Cirque Provo region Woody

Slide Canyon Avalanche, Woody
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

Sluffs, shallow wind slabs and new snow slabs can be triggered today on steep slopes, especially at the upper elevations in wind affected terrain. Friday’s loose graupel sitting above the hard crusts could be a weak layer for the slab avalanches. While these slides would be shallow, the terrain you are in will make a difference – even a small slide is serious if a ride would carry you off a cliff, into trees or down a long, icy slope.

Greg Gagne and Mark Johnston made a great video showing the “graupel above the crust” layering in the Salt Lake area mountains. Perhaps this same layering exists in the Provo area mountains.
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

At upper elevations it is still possible to trigger an avalanche breaking on a deeper weak facet layer. Slopes with a shallower snow pack are most suspect – including those that have slid one or more times this year or are steep and rocky. It’s a low probability of triggering a slide, but high consequences if you do.

The snowpack in the Provo area mountains is much weaker than it is just a little further north. Friday's avalanche triggered by UDOT is a red flag that large avalanches are still possible.

Wind slab? Deep slab? Drew Hardesty photo of natural avalanche with wide propagation below Cascade Cirque ridgeline
weather

The coldest air of the storm system is moving across the Wasatch mountains this morning, and light snow flurries are still occurring. Another trace to 2” of snow is possible this morning. Then, winds will shift to the north, cutting off the snow, and skies will become partly cloudy by this afternoon. Wind speeds are forecast to remain light, averaging below 15 mph at the mid elevations, and 20 mph at the highest elevations. Temperatures will only warm into the mid to upper 20s. The upcoming week looks quiet, with a slow warming trend, though there is a chance for a few snow showers Tuesday.
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.