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| 12.26.2008 |
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This is Janet Kellam of the Sawtooth National Forest Avalanche Center with your Backcountry Avalanche Advisory and Weather Forecast for Friday, December 26, 2008 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:
We are continuing our Avalanche Warning in the Sawtooth Forest and the mountains of south central Idaho. Mid to upper elevations are the areas of greatest concern.
Bottom Line:
Today the avalanche danger is estimated to be HIGH at mid to upper elevations throughout our forecast region. In areas where snow existed on the ground in early December, recent accumulations of 2 to 3 feet of snow now sit on top of a very weak snowpack. Large avalanches can be triggered by human activity and travel in avalanche terrain is not recommended. This includes out of bounds and closed terrain at the Bald Mountain ski area.
At lower elevations, where no snow existed on the ground in early December, the avalanche danger is estimated to be CONSIDERABLE. The past two storms have brought us 3 feet of new snow accompanied by wind. The snowpack still needs time to stabilize. Careful route finding, good travel habits and conservative decision making are required for anyone venturing into avalanche terrain in these areas.
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Danger by Aspect and Elevation:
Primary Avalanche Concern:
In the Galena area yesterday we observed widespread collapsing and cracking of the snowpack on low angle slopes and stability tests produced very easy results. A number of natural slides occurred along the highway corridor. Most were small but a few covered a good part of the road. Visibility was limited and we could not see the higher peaks, but I suspect some larger avalanches ran in the high country. The old weak snow near the base of the snowpack is struggling to adjust to the rapidly added weight of our past two storms. This weak, faceted snow will not gain strength very quickly so we are faced with lingering avalanche problems. Several storms are expected during the next week and each storm will elevate the avalanche danger.
Secondary Avalanche Concern:
In all areas the storm snow still needs time to gain strength and stabilize. In areas where we did not have early December snow, such as lower elevations and much of the southern Wood River Valley, we do not have the persistent weak layers at the base of the snowpack. The snowpack will gain strength more quickly in these locations, but today is not a green light day. In addition, strong winds have created denser slabs of windblown snow on top of the light, dry storm snow. Southerly winds moved snow during the storm and northwest winds blew overnight so all aspects in exposed areas will have some wind drifted snow. These denser slabs of snow may be triggered by the weight of a human or snowmachine, so caution is urged in any wind affected area.
Current Conditions:
Low angle slopes are offering decent powder skiing for anyone with fat skis, but a wallow for snowmachines. Ski areas and groomed trails are the best bet right now until conditions settle down.
All these storms will ultimately help the snowpack to stabilize and gain strength, but in the short term we continue to have volatile conditions and a cautious approach is essential. Six avalanche fatalities have recently occurred throughout the rocky mountain west due to similar problems in the snowpack. We are one of the last western regions to get the larger snowloads on a weak snowpack, so we have the opportunity to learn from these accidents. Please remember that sometimes the steep slopes are safe and sometimes they are not. It is critical to know the difference if you travel in to the backcountry.
Mountain Weather Forecast:
Clear skies this morning are expected to cloud over by mid day with a chance of snow showers. Temperatures will remain in the teens on the valley floor and in the single digits at higher elevations. Northwest winds are currently blowing 12 to 18mph at upper elevations with stronger gusts. Stronger winds are blowing out on the Camas Prairie and along the southern edge of the mountains.
Another storm is expected Saturday.
Photos:
1. Very easy failures on stability tests at Galena Summit
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| Reported Conditions |
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| Temperatures |
| Overnight Low |
-6 |
1 |
8 |
| 6am Temperature |
-6 |
1 |
9 |
| 24 hr Maximum |
15 |
18 |
25 |
| Winds |
| Note: South during storm shifting NW end of storm, Moderate gusts |
| Current Winds |
11NW |
11NW |
- |
| 24 hr Average |
10-18 |
10-18 |
- |
| Maximum Gust |
42S |
34NW |
- |
| Snow - Storm Interval # 6 |
| New Snow |
4" |
8" |
8" |
| Storm Total |
21" |
24" |
26" |
| Total Depth |
48" |
43" |
32" |
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