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Forecast for the Logan Area Mountains

Toby Weed
Issued by Toby Weed for
Friday, December 21, 2018
MODERATE: The danger is mostly LOW, but heightened avalanche conditions exist on drifted upper elevation slopes. You could trigger avalanches involving stiff wind-drifted snow. Hard wind slab avalanches failing on a buried sugary persistent weak layer are possible.
Evaluate snow and terrain carefully.
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Weather and Snow
Southwest winds cranked up again overnight, but they won't find much more soft snow to drift. West and southwest winds have stolen the headlines in the last few days drifting snow at upper elevations and creating heightened avalanche conditions. You can find good access and pretty good coverage for this time of year, but the snow is still just a bit too shallow to ride in steep terrain or to get aggressive with your throttle.
The Tony Grove Snotel at 8400' reports a balmy 35º F and 33"of total snow, containing 87% of average SWE for the date. It's 25º F and southwest winds are humming along in excess of 30 mph this morning at the 9700' CSI Logan Peak weather station, with gusts in the 50s.
A series of weather systems will impact the region beginning today, continuing through Christmas day. We'll see 1 to 3 inches of snow in the mountains today, with cloudy skies and high temperatures at 8500' around 32º F. West wind around 21 mph is expected. Snow will continue tonight, with 1 to 3 inches possible, and 10 to 20 mph west wind. Low temperatures will be around 8º F and wind chills will be as low as -6. Tomorrow will be partly sunny and cold, with 14 to 21 mph west wind, high temperature near 21º F, and wind chills around -12.
Recent Avalanches
Looking west from Mendon yesterday morning we noticed some natural avalanche activity yesterday due to wind drifted snow on steep slopes near the ridge in the Wellsville Mountain Wilderness.
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Avalanche Problem #1
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
You could trigger avalanches consisting of wind drifted snow. Drifting occurred in exposed terrain much of the week, and heightened avalanche conditions exist on upper elevation slopes.
  • Watch for and avoid fresh or older drifts on the lee sides of major ridges and in and around terrain features like cliff bands, scoops, gullies, stringers, and sub-ridges.
  • Avoid steep slopes that have a smooth, rounded appearance, or that sound hollow like a drum.
  • Hard wind slabs have a nasty tendency to let you get well out on them before releasing.
  • Cracking in the snow is a red flag indicating potential instability.
Avalanche Problem #2
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
A shallowly buried layer of sugary faceted snow called near surface facets was buried by last week's storm and it could become active on some drifted slopes. Although rather unlikely, dangerous human triggered hard slab avalanches failing on a persistent weak layer near the ground called depth hoar are still possible on upper elevation slopes with poor snow structure.
The shallow snow on the ground in many areas has become loose, sugary, and faceted in the past couple weeks. I found particularly weak snow in the backcountry near Beaver Mountain yesterday. In these areas the snow is currently stable despite it's weakness, but it'll get interesting when we get significant accumulation in the future.
  • Collapsing and cracking indicate that the snow is unstable.
  • Avoid steep shady or rocky terrain at upper elevations.
Sugary, faceted snow from the Thanksgiving storm creates a persistent weak layer near the ground on slopes with shallow snow cover. This is from 12/20/18, on a west facing slope at 8500' on Beaver Mountain's backside.
Additional Information
I will update this advisory tomorrow morning.
General Announcements
The new UAC IOS mobile app is now available on the app store. Check out the new "My Weather" feature. HERE
Check out the new free online avalanche course series developed by the Utah Avalanche Center. This is a great way to refresh your skills or prepare you for a Backcountry 101 or Level 1 class. HERE
Now is a great time to practice companion rescue techniques with your backcountry partners. Here is our practice video.
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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.
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