Forecast for the Salt Lake Area Mountains

Issued by Evelyn Lees for Friday, December 14, 2018 - 6:34am
The avalanche danger is MODERATE on mid and upper elevation slopes facing northwest through easterly, and on upper elevation west and southeasterly facing slopes. Slab avalanches could break 2 to 4 feet deep, failing near the ground on weak, sugary facets.
  • Old wind drifts can still be triggered on steep slopes, and any new soft drifts from the afternoon winds will be easy to trigger.
  • Wet loose sluffs can be triggered on steep, sunny slopes if the snow becomes damp, serious if they push you over a rock band or into a gully.
  • Good news – Wednesday’s storm did a good job covering the old, tracked and worn out snow surface, and once again there’s plenty of excellent – and safer – riding on southerly and lower angle slopes.
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Weather and Snow
Under clear skies, mountain temperatures are a remarkable 15 to 20 degrees warmer than yesterday morning, in the upper teens to mid 20s. Westerly winds are light, averaging 5 to 10 mph at the mid elevations, closer to 20 mph across the highest peaks. Temperatures, winds and clouds will all increase this afternoon, with highs near 40°F at 8,000’ and 30°F at 10,000’, and southwesterly winds averaging 15 to 25 mph, with gusts to 40mph at the high elevations. Wednesday’s 5 to 10” of new snow was much appreciated, improving conditions.
Check out the Weekly Review by Greg Gagne for a round up of weather and avalanche activity.
Recent Avalanches
Half a dozen smaller natural avalanches were noted in the backcountry, occurring during Wednesday’s windy storm. These were new snow slides on wind-drifted slopes, mostly along ridgelines. The resorts triggered slightly larger slides with explosives yesterday; again new snow only, mostly on wind drifted slopes.
Below: one of the larger natural slides, on Cardiac ridgeline. It failed within the boundaries of an early slide, and is called a “repeater”. Greg Gagne photo.
Avalanche Problem #1
Persistent Weak Layer
Upper elevation slopes facing northwest through northeast remain the bull-eye terrain for triggering a slab avalanche 2 to 4 feet deep. These slides are failing near the ground on the persistent weak layer of loose, sugary faceted snow. Wednesday’s new snow and wind added some extra weight to these slopes, especially those with an easterly component. Steep, rocky terrain in areas that received the most snow and wind (such as upper Little Cottonwood) are slopes more likely to slide. Even slopes that have already slid this season retained the weak faceted snow, and can slide again.
Additional Information
A few of Wednesday’s wind drifts and cornices can still be triggered. Smooth and rounded, the drifts are mostly along ridges and sub ridges. This afternoon’s increasing wind speeds could drift snow into new shallow, soft slabs on the lee sides of ridge crests and terrain features, especially at the upper elevations.
As the day heats up, watch for the snow becoming damp on the steep sunny slopes. First clue will be swarms of roller balls, then small wet loose sluffs that can be pushed, fanning out below. Increasing clouds and winds should help cool the snow later this afternoon.
General Announcements
This information does not apply to developed ski areas or highways where avalanche control is normally done. This forecast is from the U.S.D.A. Forest Service, which is solely responsible for its content. This forecast describes general avalanche conditions and local variations always occur.

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