Avalanche Advisory
Advisory: Logan Area Mountains Issued by Toby Weed for Thursday - December 22, 2016 - 6:52am
bottom line

Human triggered avalanches are possible on steep mid and upper elevation slopes in the backcountry. Strong southwest winds earlier in the week created areas with heightened wind slab avalanche conditions, and dangerous persistent and/or deep slab avalanches remain possible on slopes with poor snow structure.

  • Avoid ridge-top cornices and steep slopes with recent deposits of drifted snow.
  • Evaluate the snow and terrain carefully, especially in drifted terrain at upper elevations.
special announcement

***Discount lift tickets for Beaver Mountain, Snowbasin, Powder Mountain, and the Central Wasatch resorts are now available, donated by the resorts to benefit the Utah Avalanche Center. Details and order information here. These make a great holiday gift and all proceeds go towards paying for avalanche forecasting and education!
current conditions

The Tony Grove Snotel at 8400' reports 20 degrees this morning and there's 45" of total snow at the site, containing 110% of average water content for the date. It's 18 degrees at the CSI Logan Peak weather station at 9700' and I'm reading east winds averaging around 22 mph. You'll find nice powder riding, especially in sheltered terrain today, with a couple inches of new snow yesterday capping recrystallized powder from last weekend's storm. There's a variable rain-crust down low under a few inches of soft snow, ranging from supportable to egg shell-like.. No rain-crusts above about 8000' and now pretty good coverage and good riding on fairly supportable snow.

recent activity

Over the weekend, we noticed several good sized fresh natural avalanches in the zone... The natural avalanche cycle occurred sometime Friday during the height of the storm and included sizable activity on south and east facing slopes.

Large natural avalanches in the Wellsville Range and Wood Camp occurred during the height of the storm, Friday 12-16-16.
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

Strong and sustained southwest winds early in the week found plenty of soft snow to drift about, and the drifting created heightened wind slab conditions in upper elevation terrain. Some drifts formed on weak near surface facets or surface hoar and they may be a bit slow to stabilize.

  • Wind slabs may appear rounded and chalky and they may produce hollow, drum-like sounds.
  • Watch for and avoid deposits of drifted snow on the lee side of major ridges and in and around terrain features like gullies, scoops, sub-ridges, and cliff-bands.
  • Drifting snow built out ridge top cornices, and some of these may be sensitive to human triggering today. Cornices often break further back than expected, and they can trigger wind slab avalanches on steep drifted slopes below.
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

Although the danger of mid-pack release is slowly diminishing, triggered persistent slab avalanches remain possible on steep slopes at upper and mid elevations. While many slopes show good and increasing stability, weak layers consisting of surface hoar or small-grained near surface facets exist on others.. The only way to know is to get out your shovel, dig down below the new powder, and examine the preexisting snow. Many of the recent storm and wind slabs formed on a persistent weak layer consisting of near surface facets or surface hoar, and the wind/storm slab problem now actually fits better into the persistent slab category.

***Dangerous deep slab avalanches, failing on weak faceted snow or depth hoar near the ground remain possible, especially on upper elevation north facing slopes. Drifting snow in the past few days and the load from last Friday's heavy snow, created heightened deep slab conditions on slopes with preexisting poor snow structure. Dig to the ground and look at the snow at the very bottom of the snowpack. If you find unconsolidated larger grained facets or depth hoar, and you can easily stick your hand in it, beware of deep slab potential.

A snowboarder triggered this massive deep slab avalanche Monday afternoon in White Pine Canyon in Little Cottonwood Canyon near Snowbird. Luckily the two riders involved were okay. UAC's Report here..
weather

The National Weather Service has issued a Winter Storm Watch for Northern Utah and Southeast Idaho...

A storm system lifting northeast through Arizona will spread moisture into southern and central Utah today. A Winter Storm will likely impact travel during the upcoming holiday weekend.

Weather Forecast: Tony Grove Lake (41.897,-111.6535), Elevation: 8800'
Today: Partly sunny, with a high near 29. Wind chill values as low as -1. Calm wind becoming west southwest 5 to 8 mph in the afternoon.
Tonight: Mostly cloudy, with a low around 13. Wind chill values as low as zero. West wind 9 to 15 mph.
Friday: A 20 percent chance of snow after 11am. Mostly cloudy, with a high near 30. Wind chill values as low as -1. Southwest wind 11 to 16 mph.
Friday Night: Snow, mainly after 11pm. Low around 24. Breezy, with a south southwest wind 16 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 90%. New snow accumulation of 3 to 5 inches possible.
Saturday: Snow. High near 30. South wind around 17 mph. Chance of precipitation is 100%. New snow accumulation of 5 to 9 inches possible.
Saturday Night: Snow. Low around 14. Blustery. Chance of precipitation is 100%. New snow accumulation of 5 to 9 inches possible.
Christmas Day: Snow showers. High near 19. Chance of precipitation is 80%. New snow accumulation of 8 to 12 inches possible.

general announcements

The early season is a great time to refresh yourself and practice companion rescue techniques with your partners. Companion Rescue Practice Video

Check out Avalanche Canada's "Rescue at Cherry Bowl" story HERE

Between now and Jan 15th: Donate to the Utah Avalanche Center by shopping at Whole Foods Market Utah! When you visit any Utah Whole Foods Market locations, bring your re-usable bags, Whole Foods will donate a dime per bag to the Utah Avalanche Center - if you say DONATE my bag credit.

We will update this advisory regularly on Monday, Wednesday, Friday, and Saturday mornings by about 7:30...

Remember your information can save lives. If you see anything we should know about, please help us out by submitting snow and avalanche observations. You can also call us at 801-524-5304, email by clicking HERE, or include @utavy in your Instagram. In the Logan Area you can get ahold of your local avalanche forcaster, me (Toby Weed), at 435-757-7578

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 exist.