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Forecast for the Logan Area Mountains

Toby Weed
Issued by Toby Weed on
Saturday morning, February 13, 2021
Heavy snowfall and drifting created very dangerous avalanche conditions and HIGH avalanche danger on drifted upper and mid elevation slopes. The storm will continue today with more heavy snow and drifting overloading widespread buried persistent weak layers. Natural and human triggered avalanches are likely on many slopes.
  • Use extreme caution in the backcountry. Expect unstable snow conditions. Avoid travel in avalanche terrain.
  • Choose safe routes in low angled terrain well out from under and not connected to slopes steeper than about 30 degrees.
Low
Moderate
Considerable
High
Extreme
Learn how to read the forecast here
Avalanche Warning
FOR THE MOUNTAINS OF NORTHERN UTAH INCLUDING THE BEAR RIVER RANGE AND THE WELLSVILLE MOUNTAINS...
HEAVY SNOW AND DRIFTING HAVE CREATED WIDESPREAD AREAS OF UNSTABLE SNOW. BOTH HUMAN TRIGGERED AND NATURAL AVALANCHES ARE LIKELY. STAY OFF OF AND OUT FROM UNDER SLOPES STEEPER THAN 30 DEGREES.
Special Announcements
We've completed the report on last Saturday's tragic avalanche in the backcountry in Mill Creek Canyon above Salt Lake City that killed four skiers. Final Accident Report
The UAC in Logan is offering a Youth BC 101 avalanche class for youth aged 16-20 on Feb 21. For more info and to register, click HERE
Weather and Snow
*VERY DANGEROUS BACKCOUNTRY AVALANCHE CONDITIONS EXIST*
Snow is falling in the Bear River Range this morning. About 6 inches of heavy snow has fallen overnight, it's a warm 28°F and there is 63 inches of total snow at the 8400' Tony Grove Snotel. West-southwest winds are blowing around 20 mph at the 9700' CSI Logan Peak weather station this morning. Strong westerly winds during the week drifted tremendous quantities of fresh snow into lee slope avalanche starting zones and cross-loaded drifts in exposed terrain lower down.
With widespread layers of preexisting very weak snow, a significant increase in load on the fragile snowpack has created very dangerous avalanche conditions on drifted slopes in the backcountry.
It's snowing this morning and more snow is expected today in the mountains, with 6 to 10 inches of accumulation possible. High temperatures at 8500' will be around 27°F, with continuing 20 mph+ west and southwest winds. The National Weather Service has continued a Winter Weather Advisory for the Logan Zone, through Sunday night. Westerly winds have moderated a bit but will continue all weekend, and continued drifting is a sure bet.
A dangerous avalanche situation exists this holiday weekend, with very dangerous avalanche conditions in the backcountry and lots of nice powder to lure people into steep avalanche terrain.
A snowpit test on a drifted mid elevation slope on the eastern slope of the Bear River Range showed unstable snow conditions on 2-10-2021. The extended column test was done near a recent remotely triggered avalanche of wind drifted snow at 7600' on an east-northeast facing slope.
Recent Avalanches
Thursday, riders remotely triggered a large hard slab avalanche on a pretty low angled slope in the Peter Sinks Area (an area that is not well known for avalanches). The avalanche on an east facing slope at around 8300' in elevation was around 100 feet wide and 2 to 7 feet deep, and it stacked large chunks and piles of debris into the trees below. It is the third such avalanche to occur this week on a fairly low angled slope (between 30 and 35 degrees) and in a rather unexpected place. All have been in the eastern part of the Bear River Range...
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Avalanche Problem #1
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
Heavy snowfall and strong winds added significant weight to slopes that were already near the tipping point. Buried persistent weak layers consisting of sugary faceted snow are widespread across the Logan Zone, and the threat of large and deadly avalanches failing on weak snow near the ground is quite real. Avalanches are likely where a slab of more cohesive wind drifted snow formed on top of the weak snow.
  • Avalanches failing on a buried persistent weak layer might be triggered remotely, from a distance, or worse from below!
  • Cracking and collapsing of the snow are a red flag, indicating unstable snow conditions.
These large faceted snow grains make up a nasty buried persistent weak layer that is widespread in the Logan Zone. It exists on slopes at all elevations across the zone. (Beaver Mt. Backside, 2-7-2021)
Avalanche Problem #2
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
Westerly winds this week drifted fresh snow into lee slope avalanche starting zones, and built drifts and wind slabs on steep slopes at upper and mid elevations. Expect more drifting of fresh storm snow from a bit more moderate west and southwest winds today. Natural and human triggered avalanches of wind drifted snow are likely, especially where drifts have built on top of a buried persistent weak layer.
  • Wind slabs are often rounded and chalky looking, and they can sound and feel hollow and drum-like when you walk on them.
  • Watch for and avoid stiffer drifted snow near ridge tops and in and around terrain features like gullies, scoops, cliff bands, and sub ridges.
  • Cornices are starting to grow with the recent strong winds. Stay well back from the edge as they can break much further back than you expect.
Avalanche Problem #3
New Snow
Type
Location
Likelihood
Size
Description
In "The Avalanche Handbook," McClung and Schaerer state, "the vast majority of dry slabs (typical avalanches) release due to loading by new snowfall" We are likely to see examples of this in action in the backcountry today. "The most common trigger for natural dry slab avalanches is the addition of weight by new snowfall, blowing snow, or rain."
As loading intensity increases snow stability decreases, and there is certainly potential for rapid loading of some slopes with today's storm. Loose dry and soft slab avalanches of new snow are likely in steep terrain today, especially on slopes that pick up significant accumulations of new snow. Rapid loading from heavy new snow could also cause deeper instabilities, and buried persistent weak layers could easily be reactivated by the quick addition of weight. Natural avalanches often occur during periods of particularly heavy snowfall.
Additional Information
Do you have the essential avalanche rescue gear (transceiver, probe, and shovel) and do you know how to use them? Watch this video to see how the three pieces of equipment work together. HERE
Please keep practicing with the Beacon Training Park at the Franklin Basin Trailhead. Test yourself and your riding partners. It is free, fun, and easy to use.
General Announcements
Thanks to the generous support of our local resorts, Ski Utah, and Backcountry, discount lift tickets are now available. Support the UAC while you ski at the resorts this season. Tickets are available here.
Visit this website with information about Responsible Winter Recreation by the Utah Office of Outdoor Recreation.
EMAIL ADVISORY. If you would like to get the daily advisory by email you subscribe HERE.
Remember your information can save lives. If you see anything we should know about, please help us out by submitting snow and avalanche observations....HERE. You can also call us at 801-524-5304, email by clicking HERE, or include #utavy in your tweet or Instagram.
I will update this forecast by around 7:30 tomorrow morning.
This forecast is from the USDA Forest Service, which is solely responsible for its content. The forecast describes general avalanche conditions and local variations always occur.
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