Outdoors

Avalanche advisory: Mountains loaded with powder

WINTER SPORTS — Wonderful deep powder is calling all backcountry snow worshipers today, and the Idaho Panhandle Avalanche Center is recommending that you go and get after it — but consider staying on the lower angle slopes!

The best snow avalanche technicians found during the weekly Thursday survey was in the valley bottom where it was deep and light, said Kevin Davis, center director. 

“Yesterday was the first time I have ever gotten 2 percent water content snow on the scale.  Once up into the mountains we found scoured snow surfaces on exposed areas and, although we couldn't get to them, I imagine the wind-loaded areas are deep.  Snow was excellent in the trees.

“Don't be blinded by the incredible powder because there is a persistent weak layer that is now buried 4 feet deep with a firm slab on top.  This weak layer was the one responsible for widespread and large avalanches across our forecast region for the past two weeks.  It is more difficult to trigger now but if it does go it could lead to massive and destructive avalanches.” 

Read on for the complete region avalanche report.

 

 

AVALANCHE ADVISORY

 

U.S. FOREST SERVICE

FORECASTER:  Davis

IDAHO PANHANDLE AVALANCHE CENTER

EFFECTIVE DATE:  03/02/2012

DATE ISSUED:     03/02/2012  0730

OUTLOOK:  03/03-04/2012

This report does not apply to local ski areas within the forecast region and the hazard rating will remain valid through midnight March 2nd, 2012.  Special thanks to Idaho Parks and recreation for sponsoring this Avalanche advisory.   

Big week for snowfall in North Idaho!  Copious amounts of champagne powder have blanketed the hills.  A warming trend on Sunday will change the powder to chowder so enjoy it while you can.  Thanks for snow observations this week.

WEATHER

TODAY:  A greater chance of snow exists in the southern portion of our forecast region today, but only less than 1 inch.  Temperatures throughout will be mid 20s and moderate W winds.

TONIGHT:  Shoot up the chance of snow to the south to 90% with 1-3 inches possible.  70% chance of less than 1 up north, temperatures in the low 20s, and increasingly stronger W winds.

SATURDAY:  100% chance of 1-3 more inches of snow to the south and a little more into the PM on Saturday.  To the north you’ll see a few inches of new snow.  Across the forecast region the W winds will be increasing with gusts in the 30mph range possible.  Watch for rising temperatures, and possibly above freezing at the higher elevations on Sunday.  The avalanche danger could increase for the outlook period.

Selkirk and Cabinet mountains:Wow!  Yesterday’s trip up Lightning was amazing carving through 3-4 feet of 2% powder for miles.  The snow was deeper in the valley than up top where winds had scoured exposed areas and we found weak layers in the change in density.  6 inches of water fell in the Cabinets since last Saturday so equate 10 inches of snow to 1 inch water.  Here’s the hitch with all this great snow; it’s loading a persistent weak layer of surface hoar about 4 feet deep now.  It’s the layer that was avalanching all over for the past two weeks.  Harder to trigger now but if it does it could translate to massive slides.  With unsettled snow on top you could trip a smaller slide on the wind-loaded slab and it could trigger the deeper layer.  Warm temperatures will stress upper and deeper weak layers by Sunday.  Avalanche danger is rated CONSIDERABLE on all wind-loaded aspects steeper than 35 degrees above 5,000 feet.  Avalanche Danger is rated as MODERATE on all aspects less than 35 degrees above 5,000 feet.

St. Regis Basin and Silver valley:  In the Borax area at Lookout Pass Carole and Dan found over a foot of 10% powder from the recent storm on Wednesday.  The layers of concern they noted were a buried surface hoar layer about 6-8 inches deep and weak facets at a melt-freeze crust just over 1 foot deep.  Winds had scoured exposed areas and loaded others.  Shears were easy in the upper weak layer and moderate in the weak crust layer but there were other weak layers that popped out in their stability tests.  This revealed that there is a real potential for multiple weak layers to fail under a large surface slough in new snow or triggering a shallow slab.  Avalanche danger is rated CONSIDERABLE on all wind-loaded aspects steeper than 35 degrees above 5,000 feet.  Avalanche Danger is rated as MODERATE on all aspects less than 35 degrees above 5,000 feet.  We have a very thick slab overlying multiple weak layers, the most notable of which is a double surface hoar layer which I found 4 feet deep on a north aspect in the Cabinets and it sheared cleanly with moderate force. The thing that concerns me most is triggering a shallower weak layer in the unconsolidated new snow and having this propagate to the deeper layer.  Winds this weekend will transport this fluffy surface snow and create new slabs that can be triggered.  Warming will add weight to the upper pack and possibly result in natural avalanches.  Rain will increase avalanche danger very rapidly.  Travel with caution today and this weekend. 

The next avalanche advisory will be issued March 9th

Contact:  Kevin Davis (208) 265-6686, Ed Odegaard (208) 245-6209, or John Olson (208) 265-6635

This message is available by calling (208) 765-7323 or toll-free at 1-866-489-8664.

E-mail address:  kevingdavis@fs.fed.us, eodegaard@fs.fed.us,  jrolson@fs.fed.us, ebmorgan@fs.fed.us

 




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Rich Landers

Rich Landers’ Outdoors blog


Rich Landers writes and photographs stories for a wide range of outdoors coverage, including a Sunday feature section and a Thursday column. He also writes the Outdoors Blog.


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