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Forecast for the Logan Area Mountains

Toby Weed
Issued by Toby Weed for
Sunday, February 24, 2019
CONSIDERABLE: Areas with heightened avalanche conditions exist on drifted slopes, and prefrontal winds from an approaching Pacific Storm will cause a rising avalanche danger today. You could trigger avalanches or cornice falls consisting of wind drifted snow on some slopes at upper and mid elevations, and after a strong east wind event, avalanches may occur in unexpected places. Fine powder is plentiful in the backcountry, and you can find safer conditions, mostly stable snow, and Low danger at lower elevations, in sheltered areas, and in lower angled terrain.
  • Evaluate snow and terrain carefully, and use extra caution in drifted upper elevation terrain this afternoon
Significant snow accumulations accompanied by continued sustained and strong southwest winds tonight, will likely create more widespread dangerous avalanche conditions at upper elevations, especially in the northern Bear River Range. Natural avalanches will become possible in some areas.
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Weather and Snow
Increasing southwest winds and snowfall this afternoon will cause rising avalanche danger, and a winter storm tonight could cause dangerous conditions to develop rapidly. There's fine powder and plenty of safe places to enjoy it this weekend in the Logan backcountry, but strong east winds Thursday night and Friday, drifted fresh snow at upper elevations into unusual and perhaps unexpected places. Avalanche conditions are a bit tricky up high, with wind drifted snow your biggest concern. I am still finding areas with poor snow structure and although unlikely, dangerous deep hard slab avalanches failing on a sugary persistent weak layer near the ground remain possible for someone to trigger on isolated very steep shallow, rocky, treed, or previously wind-scoured and now wind-loaded slopes.

The Tony Grove Snotel at 8400' reports 2 inches of new snow overnight. It's 16º F this morning and there's 86" of total snow containing 102% of average SWE for the date. It's 10º F, at the 9700' CSI Logan Peak weather station, and southwest winds are currently averaging around 30 mph, with a 54 mph gust already this morning.
The National Weather Service in Pocatello has issued a Winter Storm Warning for the Bear River Range in SE Idaho due to a long term snow event beginning today. It could be partly sunny this morning in the mountains, but expect increasing clouds, southwest winds, and snow this afternoon, with 2 to 4 inches possible. High temperatures at 8500' are expected to be around 24º F, with 25 to 35 mph southwest winds, gusting to around 50 mph. It will snow tonight, with significant accumulations possible, especially near the Idaho State Line. 13 to 19 inches of snow could fall tonight in some areas, low temperatures expected to be around 19º F, with 30 mph southwest winds gusting to around 45 mph. Snow is likely tomorrow, with 7 to 11 inches possible, and it'll be windy, with 30 mph west-southwest winds and 45 mph gusts.
Recent Avalanches
Observers on Friday reported recent natural wind slab activity at upper elevations in the Mount Naomi Wilderness.

Numerous natural avalanches involving heavy, drifted, and rain-saturated snow from a Valentines Day natural cycle were observed on slopes at all elevations across the Logan Zone. Backcountry riders and skiers report triggering small soft slabs and sluffs including the soft new snow in steep terrain in the past week.
This large natural hard slab avalanche was observed last Friday in upper Providence Canyon. The crown looks to be 6 to 8 feet deep and it's about 1000' wide.
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Avalanche Problem #1
Wind Drifted Snow
Type
Location
Likelihood
Size
Description
Strong east winds Thursday night and Friday, blowing in the opposite direction of the normal prevailing winds, created drifts in unusual and unexpected places. Snow was drifted directly into west facing avalanche starting zones and cross-loaded on north and south facing slopes. Heightened avalanche conditions exist on drifted upper and mid-elevation slopes. Avalanches involving wind drifted snow could be small, soft, easily triggered, and manageable. or harder, larger, and much more dangerous. Hard wind slabs sometimes let people get out on them before releasing.
  • You should stay clear of ridge top cornices, which have grown quite large in places. Cornices are likely to break much further back than expected and may trigger large avalanches on steep slopes below.
  • Avoid wind drifted snow on the lee side of major ridges and in and around terrain features like sub-ridges, scoops, stringers, cliff bands, and gullies.
Avalanche Problem #2
Persistent Weak Layer
Type
Location
Likelihood
Size
Description
It's unlikely for a person to trigger one, but dangerous avalanches failing on a buried persistent weak layer remain possible on isolated slopes with poor snow structure. We've found areas with shallow, weak snow at mid elevations, on often scoured upper elevation slopes, on slopes that avalanched earlier in the season, and in treed or rocky areas. Dangerous 2 to 4 feet deep hard slab avalanches are possible to trigger from a shallow area on the slab, and some might be triggered remotely, from a distance, or below. Be especially careful in areas with shallow snow cover or anywhere where you sink to the ground in weak snow when you get off your sled or skis. Hard deep slab avalanches might be triggered from a shallower part of the slab.
  • Continue to avoid recent or older wind drifted snow on very steep, rocky, or shallow slopes with poor snow structure.
Additional Information
I will update this forecast Monday morning.
The new weather station at the WSU Bloomington Canyon Yurt is up and running. Data available HERE
Now is a great time to practice companion rescue techniques with your backcountry partners. You should check out and use the new Avalanche Beacon Training Park we set up at the Franklin Basin trailhead. Special thanks to Northstars Ultimate Outdoors, USU Outdoor Program, and Beaver Mountain Ski Patrol for helping us to make this possible.
General Announcements
The Beaver Mountain Backside is the backcountry, and it is avalanche terrain. Same goes for the steep rocky terrain adjacent to Cherry Peak Resort. If you leave a ski area boundary, you and your partners should carry and practice with avalanche rescue equipment and follow safe backcountry travel protocols.
Check out the improved weather links, road conditions, and weather links for each forecast region on the new UAC IOS App. Do you use the NOAA point forecast? If so, now you can bookmark your favorite weather locations in "My Weather" in the App. HERE
Are you new to the backcountry or looking to refresh your skills? The UAC has released a free 5-part avalanche skills eLearning series. HERE
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This forecast is from the U.S.D.A. Forest Service, which is solely responsible for its content. The forecast describes general avalanche conditions and local variations always occur.