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| 3.1.2009 |
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This is Chris Lundy of the Sawtooth National Forest Avalanche Center with your Backcountry Avalanche Advisory and Weather Forecast for Sunday, March 1, 2009 at 7:30 am.
The Twin Falls District Bureau of Land Management & the Friends of the Sawtooth Avalanche Center bring you this advisory.
Special Announcement:
Yesterday had all the makings of an accident day – a blue sky Saturday with new powder and dangerous avalanche conditions. Luckily there were no serious incidents and we’d like to thank everyone for making smart choices. Dangerous avalanche conditions will exist again today, and please continue to pass on the word to people you see at the trailhead and in the backcountry.
Bottom Line:
Today the avalanche danger is estimated to be CONSIDERABLE in the North Valley, Salmon Headwaters and Sawtooth Mountains. Recent snowfall and wind have loaded dangerous weak layers that are now buried 1.5 to 3 feet deep. These conditions have resulted in a widespread natural and human-triggered avalanche cycle over the past few days. Dangerous conditions will persist today and travel on slopes steeper than about 30 degrees is not recommended.
In the South and Central Valleys, the avalanche danger is estimated to be MODERATE. While a similar weak layer exists in this region, there has been less recent loading than in our northern mountains. Evaluate steep slopes carefully, and use extra caution on windloaded slopes.
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Danger by Aspect and Elevation:
Primary Avalanche Concern:
Last week’s series of storms finally made the Friday the 13th weak layer live up to its imposing title. Consisting of loose, sugary facets on shady aspects and an ugly multi-layer sandwich of crusts and facets on more sunny slopes, this layer is now buried 1.5 to 3 feet deep in much of our northern area. In the mountains closer to Ketchum and Hailey, this layer can be found about a foot down, except on wind loaded slopes where it may be more deeply buried.
And the Friday the 13th layer didn’t just produce some B-movie horror picture – we got Oscar quality. Since last Thursday, a widespread natural and human-triggered avalanche cycle has taken place in the North Wood River Valley, Salmon Headwaters, and Sawtooth Mountains. Human triggered avalanches occurred most days last week. On a flight into the western Smokies yesterday, Sun Valley Heli surveyed the damage from this cycle and saw more slides than they could count in Baker Creek and the drainages further west. A snowmobiler at the head of Baker Creek yesterday sent us photos of some recent avalanches in Apollo Creek and Brodie Gulch. All of these avalanches are breaking out about 1-2 feet deep on sheltered slopes, and 3 feet deep or more in wind loaded areas. Separate groups of skiers near Galena Summit yesterday reported collapsing of the snowpack and very easy shears within the top 2 feet of the snowpack.
Unfortunately, this type of instability doesn’t go away in a day or two. The avalanche danger may have lost a bit of its edge, but in some ways this can be the most dangerous time. The signs of instability may not be as apparent, but you still stand a good chance of triggering an avalanche if you get onto a steep slope. The greatest danger exists on mid to upper elevation slopes in our northern mountains, especially those with additional drifting from recent winds. Continued warming today will add additional stress to the snowpack, keeping it ripe for triggering. The best course of action is to stick to lower slope angles; terrain steeper than about the mid 30s simply is too dangerous given the layering and recent loading.
Current Conditions:
Sunny skies and balmy temperatures resulted in significant settlement of the snowpack surface, but great soft snow conditions for sliding and riding can be found on sheltered and shady slopes. On sunny aspects and at lower elevations, especially in the South and Central Valley, you may find some challenging crusts to contend with.
Yesterday, most mountain weather stations recorded temperatures reaching the mid 30s. This morning, mountain temperatures are still quite warm and are in the mid 20s to low 30s. Ridgeline winds were light yesterday, but increased overnight, especially on Titus Ridge where they’re currently averaging around 20 mph from the south.
Mountain Weather Forecast:
The ridge of high pressure that gave us sunny skies yesterday will begin breaking down today, bringing partly to mostly cloudy skies. Tomorrow a weather system will enter the region bringing a chance for decent snow accumulation by Tuesday morning. A southwesterly flow will continue to pump warm air into the region, and temperatures in the high country are forecasted to reach the mid 30s. A high around 40 is expected in the valley. Ridgeline winds should average 10-20 mph from the south.
Photos:
1. Durrance Avalanche - Friday Feb 27
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| Reported Conditions |
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| Temperatures |
| Overnight Low |
24 |
27 |
22 |
| 6am Temperature |
31 |
31 |
23 |
| 24 hr Maximum |
31 |
35 |
38 |
| Winds |
| Current Winds |
18 S |
11 SE |
- |
| 24 hr Average |
13 SSE |
6 SSE |
- |
| Maximum Gust |
36 SSE |
16 SSE |
- |
| Snow - Storm Interval # 19 |
| Total Depth |
57" |
49" |
26" |
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