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Avalanche advisory: Considerable danger on mountain slopes

WINTER SPORTS -- Another week of tremendous snowfall in the mountains has created weak layers, with warming temperatures addding heavier layers to lighter layers of snow.  Sounds like a fancy dessert, but instead it's a recipe for considerable avalanche danger in much of the region, according to this morning's avalanche advisory from the Idaho Panhandle Avalanche Center.

"Careful route finding is necessary today to avoid steep slopes, especially where wind-loaded," said Kevin Davis, center director.

Read on for the full advisory.









EFFECTIVE DATE:  03/16/2012

DATE ISSUED:     03/16/2012  0730

OUTLOOK:  03/17-18/2012

This report does not apply to local ski areas within the forecast region and the hazard rating will remain valid through midnight March 16th, 2012.  Special thanks to Idaho Parks and recreation for sponsoring this Avalanche advisory.   

All snotel sites in North Idaho are now at or above average for water equivalent. Big winds this week so be careful on N and E aspects. Thanks to Tom Eddy at Schweitzer Patrol fighting the avy dragon and for avalanche obs this week. Heads up out there!


TODAY:  A very good chance of 1-3 inches of snow across our forecast region with SW winds whipping at 15mph and gusts up to 30mph.  Temperatures will be in the high 20s to low 30s.

TONIGHT:  Snow tapering off with only less than ½ inch expected, temperatures dropping into the mid to high 20s and SW winds dropping to 5-10mph and then turning from the E.

OUTLOOK:  Snow returns on Saturday with a couple of inches expected, slightly more to the south, temperatures in the low 30s and light E/SE winds.  Snowfall will taper off by Saturday evening with temperatures again dropping to the low to mid 20s and wind direction changing but light.  Sunday looks to be cloudy but cool with light westerly winds.  The avalanche danger will persist on heavily wind-loaded slopes for the outlook period.

Selkirk and Cabinet mountains:Another big week of snowfall in the Selkirk and Cabinets.  Bear Mountain registers 7.2 inches of water in the Cabs, Hidden Lake had 6.5 inches and Schweitzer snotel a huge 9.2 inches.  In the last 24 hours these sites show 11”, 5”, and 30”, respectively.  Snowfall throughout the week has come during strong, warm, wet Pacific weather troughs plowing through and these were divided by cooler weather and that has created weak layers at the change in density, yesterday about 1’ and 2’ deep and shearing easily.  Schweitzer patrol reported active avalanches from control work on Tuesday.  It’s cooling now so the pack will tighten a bit but a lot of snow in a short period has conditions unstable.  I didn’t find it yesterday but that deep layer of surface hoar from February is probably still weak and step down avalanches from surface weak layers will be colossal in size. Avalanche danger is rated CONSIDERABLE on all wind-loaded aspects steeper than 35 degrees above 5,000 feet.  Avalanche danger is rated MODERATE on non-wind-loaded aspects steeper than 35 degrees above 5,000 feet.

St. Regis Basin and Silver valley:  Carole and Dan, up at 5,200 feet in the Borax area around Lookout Pass yesterday found a very wet snow pack with much evidence of point releases and very large “chicken heads, pinwheels”… on numerous aspects.  “Some of the snowballs were the size of a VW bug and digging deep”, Carole said.  They observed a structurally weak snowpack, meaning weak layers exist at a depth shallow enough to trigger but they may not be showing hair trigger weakness.  They did note the weak layers in the recent snow being at points of density change that failed with moderate force, but not cleanly, Q3.  Warm weather and rain will stress the snowpack further.  Avalanche danger is rated CONSIDERABLE on all wind-loaded aspects steeper than 35 degrees above 5,000 feet.  Avalanche danger is rated MODERATE on non-wind-loaded aspects steeper than 35 degrees above 5,000 feet.  Strong winds have created huge areas of unstable wind deposition on N and E slopes below ridgelines.  Cornices will be breakable during warm periods and further weakened by rain.  Rain will increase the avalanche danger on any slope.  Stay off steep wind-loaded aspects since the change in density weak layers from this week’s big dumps have not had time to settle.  We have a persistent weak layer at the mid February surface hoar that will created large and destructive avalanches if triggered.

The next avalanche advisory will be issued March 23rd.  Karl Dietrich, accomplished local mountaineer and owner of Dietrich Coffee Roasters, will present a slide show of some of his favorite alpine climbs, some first ascents, from Canada’s BC and Alberta.  Show is March 29that 6PM at Laughing Dog Brewery in Ponderay and presented by the Friends of the Idaho Panhandle Avalanche Center.  See you there!

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Rich Landers
Rich Landers joined The Spokesman-Review in 1977. He is the Outdoors editor for the Sports Department writing and photographing stories about hiking, hunting, fishing, boating, conservation, nature and wildlife and related topics.

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