Avalanche Advisory
Advisory: Logan Area Mountains Issued by Toby Weed for Wednesday - December 21, 2016 - 6:28am
bottom line

Strong southwest winds in the past couple days created areas with dangerous wind slab avalanche conditions in the backcountry, mainly on steep drifted slopes at upper elevations. Heightened persistent and deep slab conditions persist, with dangerous human-triggered avalanches possible on steep upper and mid elevation slopes.

  • 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 24 degrees this morning and 2 inches of new snow from overnight, containing .6" of water. There's 46" of total snow at the site, containing 113% of average water content for the date. It's 15 degrees at the CSI Logan Peak weather station at 9700' and the wind sensor became rimed early this morning, after recording a westerly wind shift in the evening and diminishing northwest wind overnight. Monday, the station reported several hours with sustained 45 mph south-southwest winds. Yesterday, hourly average wind speeds remained pegged at around 30 mph from the south-southwest.. Drifting created pockets with dangerous wind slab avalanche conditions in exposed upper elevation terrain. You'll find nice powder riding in sheltered terrain today, with a few fluffy inches of recrystallized powder on a variable rain-crust down low and deeper powder as you ascend to upper elevations.

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 in the past couple days found plenty of soft snow to drift about, and the drifting created dangerous wind slab conditions in upper elevation terrain.

  • 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 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 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.

***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

A cold front moving south across northern Utah will stall across central Utah today. A storm system lifting northeast through Arizona will spread moisture into southern Utah tonight and Thursday ahead of a potentially stronger storm system over the holiday weekend.

Weather Forecast: Tony Grove Lake (41.897,-111.6535), Elevation: 8800'
Today: Partly sunny, with a high near 26. Northwest wind 8 to 13 mph becoming light north in the afternoon.
Tonight: Partly cloudy, with a low around 14. North wind around 5 mph becoming south after midnight.
Thursday: Mostly sunny, with a high near 27. Light south southwest wind increasing to 5 to 10 mph in the morning.
Thursday Night: Partly cloudy, with a low around 16. Southwest wind 9 to 11 mph.

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.