Forecast for the Logan Area Mountains

Toby Weed
Issued by Toby Weed for
Saturday, December 29, 2018
MODERATE: Heightened avalanche conditions exist on drifted upper elevation slopes, and you could trigger avalanches involving wind-drifted snow. The snow is stable and the danger LOW in sheltered terrain, at lower elevations, and anywhere the snow was not recently drifted. You'll find excellent shallow powder conditions in the backcountry, but expect very cold temperatures, with wind chills around 20º F below zero.
Evaluate snow and terrain carefully, and avoid drifted upper elevation slopes.
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High
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Weather and Snow
It's mighty cold in the mountains again this morning, and we'll see clouds thicken today ahead of the next Pacific Storm. You'll find excellent shallow powder conditions, good stability and Low danger on most slopes in the backcountry, but heightened avalanche conditions exist on drifted upper elevation slopes. Shallow human triggered avalanches involving wind drifted snow are possible.
Fine shallow powder riding conditions and mostly stable snow in the Logan Zone, but heightened avalanche conditions exist at upper elevations where light snow was drifted into stiff drifts.
The Tony Grove Snotel at 8400' reports 7º F and there's 39" of total snow containing 83% of average SWE. It's 2º F at the 9700' CSI Logan Peak weather station, and west-northwest winds are currently averaging about 26 mph, with gusts around 40 mph.
A short lived high pressure system will be over the zone today, but we'll see increasing warm air advection aloft bringing clouds and a chance of a little snowfall. Tomorrow a potent wave with a significant Canadian cold air source will dive from British Columbia to Utah, and we'll see significant snow accumulations and fairly strong winds in the Logan Zone. Some of the coldest air of the season will filter into the region in the wake of the storm system for Monday and especially Tuesday.
Expect increasing clouds and a chance of snow showers today, with a high temperature at 8500' near 19º F and 10 to 15 mph west wind, Wind chill values will be as low as -21º F. Snowfall begins tonight, with temperatures rising to around 20º F and increasing southwest winds, 13 to 18 mph. 1 to 3 inches of accumulation is forecast. It'll snow tomorrow, with 6 to 10 inches of accumulation possible, a high temperature around 21º F, and 25 to 35 mph west-southwest wind and gusts near 50 mph.
Recent Avalanches
Noticed some natural avalanche activity due to wind drifted snow in upper Providence Canyon, likely from overnight 12/27/18.
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Avalanche Problem #1
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
Heightened avalanche conditions exist on upper and some mid-elevation slopes, and you could trigger avalanches consisting of wind drifted snow. Drifting occurred in exposed terrain much of last week, and there are some deeper hard wind slabs lurking under the fresh snow in places. East-northeast winds Thursday night built fresh drifts at upper elevations in perhaps unexpected or unusual places.
  • 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
Although quite unlikely, dangerous human triggered hard slab avalanches failing on a persistent weak layer near the ground called depth hoar remain possible on isolated upper elevation slopes. Avoid very steep slopes with poor snow structure, including shallow, shady, or rocky terrain at upper elevations.
The shallow snow on the ground in many areas has become loose, sugary, and faceted in the past couple weeks. I've found particularly weak snow at mid and lower elevations in the backcountry, anywhere where the total snow is fairly shallow. In many areas, weak faceted snow near the ground is capped by a crust and a few inches of Christmas powder... Lacking a slab of stronger snow on top, the sugary snow is currently stable despite it's weakness.
Sugary, faceted snow creates a persistent mid pack weak layer. This from 12/28/18, on a southeast facing slope at 8700' in upper Providence Canyon
Additional Information
I will update this advisory tomorrow morning. A cold storm will bring significant accumulations and strong wind, and the avalanche danger will be on the rise.
General Announcements
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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.