GNFAC Avalanche Advisory for Tue Feb 24, 2015

Not the Current Forecast

Good morning. This is Doug Chabot with the Gallatin National Forest Avalanche Advisory issued on Tuesday, February 24, at 7:30 a.m. Bozeman Audi in partnership with the Friends of the Avalanche Center sponsor today’s advisory. This advisory does not apply to operating ski areas.

Mountain Weather

This morning mountain temperatures are 20F with W-NW winds blowing 15-20 mph under clear skies. Today will be mostly sunny and winds will increase with daytime highs reaching the low 30s. A cold front and moist northwest flow are teaming up late tonight bringing snow through tomorrow. By morning, I expect 2-4 inches with much more falling Wednesday. My fingers are crossed that the northwest flow will wring even more snow onto the Bridger Range.

Snowpack and Avalanche Discussion

Bridger Range   Northern Madison Range   Northern Gallatin Range   

In the northern mountains one to two feet of powder from Saturday was easily pushed around by light to moderate winds yesterday. Downhill winds in the Bridger Range and westerly winds elsewhere created soft slabs of windblown snow which were sensitive to triggering. Both Big Sky and Bridger Ski Patrols tackled these wind drifts with ski cuts and explosives. Yesterday, skiers triggered a couple wind slabs near Saddle Peak which poured over the cliffs, and on Sunday skiers kicked off two small slides up Hyalite (photo). Eric and I found conditions ripe for wind loads on our tour up Hyalite on Sunday (video) which was very similar to the conditions Eric found the day before in Beehive Basin (video).

The recent snow has bonded well to the old snow surface. Today’s concern is on wind-loaded slopes.  Given moderate winds speeds these slabs are not widespread. The wind pillows are easy to find as the surface snow texture will be rippled and the snow underfoot or under track will be thicker. For today the avalanche danger is rated MODERATE on wind-loaded slopes and LOW on all others.

Southern Madison Range   Southern Gallatin Range   Lionhead Area near West Yellowstone   Cooke City

The southern ranges have not had fresh snow in a while, thus wind-loading is not an issue. The layer of buried surface hoar that was found on isolated slopes around Lionhead and the southern Madison Range is not reactive. Karl Birkeland skied into Bacon Rind to test this layer and found stable conditions. Reports from the Cooke City area are indicating a stable snowpack too. As the next round of snow falls we’ll be testing how it bonds to the old snow. Lack of recent snowfall and a strong, stable snowpack point to a LOW avalanche danger today.

I will issue the next advisory tomorrow morning at 7:30 a.m. If you have any snowpack or avalanche observations drop us a line at mtavalanche@gmail.com or call us at 587-6984.

AVALANCHE EDUCATION and EVENTS

Take a look at our Education Calendar for all classes being offered.

TONIGHT: Snow Science and the Human Factor, Big Sky, Jefferson Room at the Yellowstone Center, Tuesday, February 24, 7-9 pm. The free event will feature a talk by Powder editor and MSU graduate John Stifter, multimedia presentations on the human factor in avalanche risk, a panel of experts from MSU’s Snow & Avalanche Lab and Gallatin National Forest Avalanche Center, as well as a Q & A session. (poster)

1-hour Avalanche Awareness, Bozeman, REI, 6:30 - 8 p.m., Wednesday, March 11.

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