AVALANCHE ADVISORY

U.S. FOREST SERVICE

FORECASTER:  Davis

IDAHO PANHANDLE AVALANCHE CENTER

EFFECTIVE DATE:  03/23/2012

DATE ISSUED:     03/23/2012  0730

OUTLOOK:  03/24-25/2012

This report does not apply to local ski areas within the forecast region and the hazard rating will remain valid through midnight March 23 ^rd , 2012.  Special thanks to Idaho Parks and recreation for sponsoring this Avalanche advisory.

We’ll be ending the weekly advisory March 30 this year.  I’ll issue the safe spring riding tips in April.  Thank you to all folks that sent in observations, keep up the good work.  Thanks to Schweitzer patrol this week for the heads up.

WEATHER

TODAY:  Snowfall will be slight today with less than 1 inch expected.  Temperatures will be in the high 20s to the north with light E winds and up to the mid 30s to the south with light S winds.

TONIGHT: Mostly cloudy and temperatures dropping into the 20s with light S/SE winds.

OUTLOOK: Partly sunny in the Purcell Trench and mostly cloudy around the Silver Valley Saturday with daytime temperatures rising above freezing with E winds at 7-10mph.  On Sunday watch for shift in the weather that brings in very warm temperatures in the mountains, possibly into the 40s.  South winds will be light and only a slight chance of snow is predicted. The avalanche danger will increase during the day if temperatures rise above freezing for the outlook period.

Selkirk and Cabinet mountains: In the Cabinets yesterday we found over 3 feet of new snow sitting on top of last week’s rain crust.  On a NE aspect at about 5,700 feet we got very easy shears where 10 inches of wet snow buried a light layer of snow.  The storm came in cold and ended wet producing a change in density weak layer.  On S slopes steeper than 35 degrees we triggered this weak layer and on N aspects we saw small natural slides.  Weak layers at 2 feet deep showed moderate weakness at change in density.  Temperatures dropping since yesterday will decrease the avalanche danger for today but watch instability on steep slopes, especially where wind-loaded.  Schweitzer patroller, Tom Eddy, alerted me of observing very large cornice fall on a N aspect earlier this week.  Avalanche danger is rated MODERATE on all aspects steeper than 35 degrees above 5,000 feet.  Pockets of CONSIDERABLE avalanche danger exist on wind-loaded aspects steeper than 35 degrees above 5,500 feet.

St. Regis Basin and Silver valley: Carole and Dan, up at Lookout Pass yesterday found almost the exact same snowpack with the same change in density weak layers.  Two and a half feet of snow fell since last week and buried the rain crust.  They also got very easy shears in the weak layer present at a change in density.  Shear tests at the layer over the rain crust showed moderate weakness.  There is a potential for step down avalanches to result in larger slides, meaning you could trigger the 10 inch deep weak layer which could trigger the deeper weak layer at the rain crust.  These layers have gained some strength as the pack settled with warmer weather yesterday but human triggered avalanches are possible.  Avalanche danger is rated MODERATE on all aspects steeper than 35 degrees above 5,000 feet.  Pockets of CONSIDERABLE avalanche danger exist on wind-loaded aspects steeper than 35 degrees above 5,500 feet. Conditions were unstable yesterday, especially at the 10 inch deep weak layer.   Due to settlement this layer will have gained strength but realize that you could still trigger this layer and that could trigger deeper weak layers.  Moderate means you likely won’t see natural avalanches today, but human triggered avalanches are possible.  Big, open terrain above 5,500 feet that is heavily wind-loaded should be avoided today.  Stay off the open steep terrain and away from cornices this weekend when the temps rise above freezing   We didn’t find the mid-Feb surface hoar at 6-8 feet deep, but we’ll keep digging for it.

The next avalanche advisory will be issued March 30 ^th .  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 29 ^th at 6PM at Laughing Dog Brewery in Ponderay and presented by the Friends of the Idaho Panhandle Avalanche Center.  See you there!

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