Advisory: Logan Area Mountains | utahavalanchecenter.org

Avalanche Advisory

Advisory: Logan Area Mountains	Issued by Toby Weed for Saturday - February 22, 2014 - 6:40am

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In most areas the danger is Level 2 or MODERATE, with heightened avalanche conditions in drifted terrain. You can find safer, mostly stable snow conditions at lower elevations and in sheltered lower angled terrain. But, there's still a CONSIDERABLE or Level 3 avalanche danger on steep drifted slopes at upper elevations. Triggered wind slab avalanches and cornice falls are likely, and you still might trigger very dangerous and destructive deep slab avalanches in steep terrain from shallow areas. Careful snowpack evaluation, cautious route-finding, and conservative decision making will be essential for safe travel in the backcountry today.

current conditions

The Logan Summit weather cam is showing snowfall again this morning, and the 8400' Tony Grove Snotel reports a couple more inches of new snow containing 4/10ths of an inch of water overnight, bringing the last two day's accumulation up to about 6 inches. It's 22 degrees and there's 97 inches of total snow, containing 119% of average water content for the date. The 9700' CSI Logan Peak weather station reports 14 degrees and average wind speeds in the upper teens from the southwest this morning. Colder temperatures solidified the saturated weak snow at lower elevations, and you stay on top of a solidly refrozen crust in a few inches of fresh snow from the past couple days. Shallow powder riding conditions up high are nice, smooth, and fast, with many great lower angle options, and we're avoiding steep terrain due to widespread poor snow structure and the gradually diminishing chance of triggering an un-survivable avalanche.

Bruce Tremper just published a Storm Analysis Blog that explains aspects our recent active natural avalanche cycle. HERE And he explains this weekend's generalized snow situation well in this video

recent activity

It's been almost a week since our last reported avalanche activity in the Logan Zone.

Looking at a very large natural avalanche in Pine Canyon in the Wellsville Mountain Wilderness on 2-19-2014

***Video look at a HUGE natural avalanche in the Wellsville Range, from 2-19-2014...........HERE

Last week, in addition to numerous large natural avalanches in the backcountry, there were a few close calls with dangerous unintentionally triggered avalanches and another incredibly lucky survival story in the Providence Canyon Area, in which a rider was completely buried, rescued by his partners unconscious and unresponsive, but recovered and was able to ride out on his own....SEE REPORT

Check out "Beaver Backside is the Backcountry," an Avalanche observation video from 2-16-2014 .....HERE

A child's perspective on last week's natural wet avalanche above Zanavoo in Logan Canyon filmed on 2-17-2014 .......HERE

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 The instability from last week's rapid loading appears to settling be out with time and it is increasingly unlikely the you would trigger one, but dangerous triggered deep slab avalanches failing on preexisting faceted weak layers at the bottom of the snowpack remain possible today, especially on drifted upper and mid elevation slopes that didn't naturally avalanche in the recent prolonged cycle. Drifted slopes with shallow overall snow cover are the most suspect, since shallow areas tend to harbor the weakest snow. Although ever more unlikely, you still might trigger dangerous avalanches remotely, from a distance or even from the flats below steep slopes in some cases. A Snow profile from the Franklin Basin Area showing very poor snow structure. At least the weak facets in the Basal layers are deeply buried in many areas now, so deep slab avalanches would be fairly hard for us to trigger. Shallow areas, where the slab is less than around 3' deep are the more likely trigger points. (Carlisle)

type

aspect/elevation

characteristics

LIKELIHOOD

LIKELY

UNLIKELY

SIZE

LARGE

SMALL

TREND

INCREASING DANGER

SAME

DECREASING DANGER

over the next 24 hours

description

The instability from last week's rapid loading appears to settling be out with time and it is increasingly unlikely the you would trigger one, but dangerous triggered deep slab avalanches failing on preexisting faceted weak layers at the bottom of the snowpack remain possible today, especially on drifted upper and mid elevation slopes that didn't naturally avalanche in the recent prolonged cycle. Drifted slopes with shallow overall snow cover are the most suspect, since shallow areas tend to harbor the weakest snow. Although ever more unlikely, you still might trigger dangerous avalanches remotely, from a distance or even from the flats below steep slopes in some cases.

A Snow profile from the Franklin Basin Area showing very poor snow structure. At least the weak facets in the Basal layers are deeply buried in many areas now, so deep slab avalanches would be fairly hard for us to trigger. Shallow areas, where the slab is less than around 3' deep are the more likely trigger points. (Carlisle)

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 Triggered wind slab avalanches and cornice falls are likely on steep slopes, and a smaller avalanche overrunning a slope with poor snow structure might cause a step-down into weak old snow and result in a much larger and more dangerous deep slab avalanche. Avoid freshly formed cornices along exposed ridge-lines, which are likely to break further back than you expect and stiffer drifted fresh snow on the lee sides of major ridge lines and in and around terrain features like rock outcroppings and gullies.

type

aspect/elevation

characteristics

LIKELIHOOD

LIKELY

UNLIKELY

SIZE

LARGE

SMALL

TREND

INCREASING DANGER

SAME

DECREASING DANGER

over the next 24 hours

description

Triggered wind slab avalanches and cornice falls are likely on steep slopes, and a smaller avalanche overrunning a slope with poor snow structure might cause a step-down into weak old snow and result in a much larger and more dangerous deep slab avalanche. Avoid freshly formed cornices along exposed ridge-lines, which are likely to break further back than you expect and stiffer drifted fresh snow on the lee sides of major ridge lines and in and around terrain features like rock outcroppings and gullies.

weather

It's snowing again this morning in the Bear River Range and more snow is likely today, with 2 to 4 inches of additional accumulation possible up high. Expect a high temperature of 26 degrees at 8500' and fairly strong and sustained west winds. Showery snowfall and west winds will continue overnight, with low temperatures around 19. We might see a bit of sunshine on Sunday, with 8500' temperatures a couple degrees above freezing and more moderate west winds. Expect unsettled weather with a couple grazing storms to our north through midweek. Looks like a more significant and productive zonal pattern will set up, with accumulating snow a good bet on around Thursday.

Check out our one-stop weather page........HERE

general announcements

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Remember your information can save lives. If you see anything we should know about, please participate in the creation of our own community avalanche advisory by submitting snow and avalanche conditions. You can also call us at 801-524-5304 or 800-662-4140, email by clicking HERE, or include #utavy in your tweet or Instagram.

I'll issue these advisories on Monday, Wednesday, Friday, and Saturday mornings.

This advisory is produced by the U.S.D.A. Forest Service, which is solely responsible for its content. It describes only general avalanche conditions and local variations always exist.

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