Avalanche Advisory
Advisory: Provo Area Mountains Issued by Evelyn Lees for Sunday - December 8, 2013 - 7:09am
bottom line

The avalanche danger remains CONSIDERABLE on all northwest, north and northeasterly facing slopes, steeper than about 33 degrees, where deep, dangerous avalanches can be triggered in mid and upper elevation terrain. Slides can be triggered from a distance, so avoid travel below and adjacent to steep slopes. Also avoid all steep wind drifted slopes. CONSIDERABLE means:

  • Dangerous avalanche conditions exist
  • Natural avalanches are possible
  • Human triggered avalanches are likely
  • Cautious route finding and conservative decision-making is essential.

Recreate on lower angle slopes today, in wind sheltered terrain, and consider options on the southerly ½ of the compass.
current conditions

Storm totals of low density, cold powder –

  • Ogden area mountains: 12 to 16”, with about ½” of water weight
  • Park City and Salt Lake mountains: 4-10”, up to .6” of water weight
  • Provo area mountains: up to 22” of snow, and just under an inch of water

Temperatures have once again plummeting into negative territory, and are in the single digits above and below zero. The westerly winds are generally light, averaging less the 10 mph, with only the highest ridgelines in the 20 to 25 mph range, with gusts to 40.

recent activity
  • Ogden area mountains – skier released soft slabs, 12-18” deep, wind affected terrain
  • SLC mountains - Numerous skier released soft and medium hard wind slabs, some remotely triggered, average 6-12” deep, less than 100’ wide, with one person taking an uneventful ride.
  • Park City ridge line: Both natural and explosive triggered hard slabs, failing on basal facets on the ground, NE, 9800’
  • Provo mountains – Naturals heard, but no visibility. New snow soft slabs and sluffs common. Interesting layering at 7300’ and above, on NE-NW facing slopes – soft slabs failing on facets on a temperature crust, taking out last 2 storms worth of snow

Remotely triggered Raymond wind slab
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

In my mind, there is still a skull and cross bone on the northwest, north and northeasterly facing slopes at the mid and upper elevations, where layers of weak, faceted snow crystals are buried in the snow pack. While I hope that at least some of these slopes avalanched naturally during the wind event, I expect the snow on most slopes is left hanging in balance, just waiting for a trigger. A trigger today could be a person or a smaller new snow slide that then steps down, triggering a deeper, wider slide. These deeper, dangerous slides can be triggered remotely, from below, the side or above, and have the potential to break out widely.

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

Yesterday’s widespread wind drifts will be more stubborn today, but still want to crack out beneath you, and are large enough to take a person for a ride, and in places bury them. The drifts are now hidden beneath the overnight snow, and will be harder to identify. The drifts are most widespread along the high ridgelines on northerly through easterly facing slopes, but were also found yesterday out in open bowls.

weather

The storm is winding down, with light snow showers this morning perhaps adding another inch or two of snow to the totals. Temperatures will remain near zero at 8,000’ feet and negative 5 to 10 degrees at 10,000’. The westerly winds will generally remain less than 15 mph, except for the high peaks and ridge lines, with 20 to 25 mph averages and gusts to 40 mph. In the long range, high pressure with a stable northwest flow will be over the area through at least mid-week.
general announcements

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.

If you trigger an avalanche in the backcountry - especially if you are adjacent to a ski area – please call the following teams to alert them to the slide and whether anyone is missing or not. Rescue teams can be exposed to significant hazard when responding to avalanches, and do not want to do so when unneeded. Thanks.

Salt Lake and Park City – Alta Central (801-742-2033), Canyons Resort Dispatch (435-615-3322)

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