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| 12.27.2008 |
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This is Janet Kellam of the Sawtooth National Forest Avalanche Center with your Backcountry Avalanche Advisory and Weather Forecast for Saturday, December 27, 2008 at 7:30 am.
The Sawtooth Society in partnership with Idaho's SNRA Mountain Goat license plate program & the Friends of the Sawtooth Avalanche Center bring you this advisory.
Special Announcement:
We have canceled the Avalanche Warning for today but we expect to see the avalanche danger increase with tonight’s storm, bringing the possibility of another Avalanche Warning Sunday or Monday.
Bottom Line:
Challenging and deceptive avalanche conditions exist right now. Some areas have fairly low danger, other areas have high danger. Backcountry travel requires continuous snowpack evaluation, safe travel protocols and conservative decision making.
Today the avalanche danger is estimated to be HIGH above approximately 8,000feet, in areas which have very weak snow on the ground from November storms. Several large avalanches were triggered yesterday near Galena Summit, where this condition exists. Most of the higher mountains in our region have this problem.
Upper elevations in the Central and South Valley have CONSIDERABLE avalanche danger, as the weak base layer is present but less widespread. Wind loaded slopes also exist in this region.
Lower elevations which had no snow on the ground in early December have a MODERATE avalanche danger due to the large amounts of recent snowfall and wind drifted snow.
OUTLOOK- A significant winter storm is forecast to enter our area today bringing prolonged snowfall, warmer temperatures and gusty winds. Expect increasing avalanche danger in all locations the next two days.
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Danger by Aspect and Elevation:
Primary Avalanche Concern:
Deep Slab instability exists at mid to upper elevation locations which have weak November snow at the base of the snowpack. This weak snow persists on all but due south facing slopes. Large avalanches may be triggered from low angle slopes or from flat terrain beneath steep slopes. Where this condition is found, avoid any terrain steeper than low 30 degree slope angle.
Yesterday out Titus Ridge I was able to trigger one of the north facing Titus Chutes while skinning along near the top. (See today's photos)This 2 foot deep slide sympathetically released all the other chutes, breaking out approximately 1,000feet wide. Skiing back down the ridge, we remotely triggered an east facing slope from low angle terrain which proceeded to propagate and break out about 700 feet wide. This slope had previously collapsed and cracked while skinning up the ridge, but did not avalanche then. These examples show how deceptive and dangerous the conditions are. Unless you are very cautious, it is possible to get out on a slope before it breaks underneath you or above you.
Reports of collapsing and cracking at mid to upper elevations in the Ketchum area indicate weak snow exists, but only smaller avalanches were triggered by control work on Bald Mtn yesterday. Conditions are not quite as volatile in the Central and South Valley but it remains possible to trigger an avalanche on steeper slopes with this condition. This Considerable danger will primarily be found on the cooler aspects facing northwest through north to south east.
Secondary Avalanche Concern:
Widespread wind damage has left us with a variety of wind slabs and wind drifted slopes. These slabs have gained strength and are not as reactive, but warrant caution when found on any steeper slope on all aspects and elevations.
Current Conditions:
The cold air which moved in brought gusty winds and plenty of wind drifting and scalloped the snow surfaces, although powdery conditions can still be found. The snowpack is more supportive for skiers but still pretty deep and loose for snowmobiles.
This morning a temperature inversion exists. Baldy reports 10 degrees on top, Titus 5 degrees and the valley floor is minus 4 degrees. Temperatures are already beginning to increase and should climb into the teens today. Ridgeline winds are light out of the north west, gusting 20 to 25mph.
Mountain Weather Forecast:
It was snowing in Boise at 5AM. This next storm is expected to enter our area sometime this morning and last into Monday, favoring the northern sectors. Northwest winds will shift southwest and remain gusty.
Only a couple inches of snow are expected today with 4 to 8 inches of snow forecast for overnight, 4 to 6 inches more by Sunday afternoon accompanied by some rapid precipitation rates and warmer temperatures. The storm is expected to continue through Monday night.
Photos:
1. Slide triggered from top of Titus Chutes 9,600ft elevation NE facing
2. Titus Chutes in the background, slopes below remotely triggered
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| Reported Conditions |
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| Temperatures |
| Overnight Low |
-6 |
-1 |
-4 |
| 6am Temperature |
2 |
10 |
-4 |
| 24 hr Maximum |
2 |
10 |
23 |
| Winds |
| Current Winds |
15NW |
16NW |
- |
| 24 hr Average |
11 |
14NW |
- |
| Maximum Gust |
23NW |
29NW |
- |
| Snow - Storm Interval # 6 |
| Total Depth |
44" |
41" |
30" |
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