Avalanche Advisory
Advisory: Logan Area Mountains Issued by Toby Weed for Tuesday - December 20, 2016 - 5:46am
bottom line

Strong southwest winds yesterday and overnight created pockets with dangerous wind slab avalanche conditions on steep drifted slopes at upper elevations. Heightened persistent and deep slab conditions also exist in the backcountry, with dangerous human-triggered avalanches possible on some 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 at upper elevations.
  • Watch from a safe zone and only expose one person at a time while crossing steep slopes.
  • Practice companion rescue with your backcountry partners.



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 28 degrees this morning and 108% of average water content for the date. It's also 28 degrees at the Franklin Basin ID Snotel to the north, reporting 44 inches of total snow on the ground. It's 21 degrees at the CSI Logan Peak weather station at 9700' with southwest winds averaging 32 mph, with gusts in the 40s. Yesterday, the station reported several hours of south-southwest winds with hourly averages pegged at around 45 mph. Drifting created 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 solid and supportable 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 yesterday and overnight found plenty of nice soft powder on the snow surface to drift about, and this created dangerous wind slab conditions in upper elevation terrain exposed to drifting.

  • 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 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.
weather

A mild near zonal flow will remain over the area today. A cold front will enter northern Utah this evening, then move south into central Utah tonight into Wednesday. A potentially stronger storm system could impact the area over the holiday weekend.

Weather Forecast: Tony Grove Lake (41.897,-111.6535), Elevation: 8800'
Today: A 40 percent chance of snow after 11am. Mostly cloudy, with a high near 31. Breezy, with a west southwest wind 15 to 23 mph. Total daytime snow accumulation of less than a half inch possible.
Tonight: Snow. Low around 13. Breezy, with a west northwest wind 16 to 23 mph. Chance of precipitation is 80%. New snow accumulation of 1 to 2 inches possible.
Wednesday: Mostly sunny, with a high near 24. Wind chill values as low as zero. Northwest wind 6 to 14 mph.
Wednesday Night: Mostly clear, with a low around 13. West southwest wind 5 to 8 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.

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.