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| 2.18.2009 |
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This is Janet Kellam of the Sawtooth National Forest Avalanche Center with your Backcountry Avalanche Advisory and Weather Forecast for Wednesday, February 18, 2009 at 7:30 am.
Blaine County Search and Rescue & the Friends of the Sawtooth Avalanche Center bring you this advisory.
Bottom Line:
Today there is a MODERATE danger of triggering deposits of wind drifted snow and wind slabs along or beneath upper elevation ridgelines. There is also a MODERATE danger of triggering loose snow avalanches on northerly aspects approaching 40 degrees or steeper.
LOW avalanche danger exists elsewhere.
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Danger by Aspect and Elevation:
Primary Avalanche Concern:
We received a report of skiers triggering a moderate sized slab avalanche on a north facing slope on Monday out the East Fork. Because they recognized the wind loading occurring near the top of the ridgeline, the skiers were carefully skiing one at a time and exiting onto safer terrain so no one was caught.
Yesterday out Titus Ridge I had one large rolling collapse of a wind drifted area along the ridgeline and did experience some cracking and propagation of wind drifted slabs on the top of a north facing slope above Titus Lake. Nothing was steep enough to slide where I had these conditions, but I feel you could encounter the right (perhaps I should say “wrong”), combination of wind deposited snow along steeper, exposed slopes and trigger a slide today.
Continuous southerly winds the past few days created most of these wind slabs on north and northwest facing slopes, but yesterday the winds did switch back to the northwest and some of the light density snow was moving onto the more east facing slopes. Wind transport was not extensive yesterday along Titus Ridge, but weather stations indicate gusty conditions at upper elevations throughout our region so continue to stay heads up for wind slabs and wind deposits on top of the old, non-cohesive faceted snow.
Secondary Avalanche Concern:
On steep shady slopes out of the wind, we continue to see large, loose sluffs of new and old snow triggered by skiers and riders. These sluffs are big enough to consider carefully choosing your terrain in order to avoid getting shoved into rocks, trees or stuffed into a steep terrain trap.
Additional Discussion:
Clearing skies and a dose of February sun in the mountains today could produce some sticky snow on the warmer aspects and the possibility of triggering shallow wet sluffs on steep slopes where the newer snow has added up to more than a few inches on the old crust surfaces.
Now is a great time to get out and enjoy the powder conditions before our snowpack becomes overloaded and more dangerous. Stay alert. The cracking wind slabs and easy sluffing are all indicators that a thicker, more cohesive, overlying slab of snow will be sensitive to human triggers and produce avalanche conditions.
Current Conditions:
It felt sunny and warm in town yesterday but temperatures remained cool in the mountains and snow showers lingered throughout the day at mid to upper elevations. Some areas gained up to another inch of very light density snow. North tending aspects continue to produce excellent powder conditions, warmer slopes sport a variety of new snow on top of variable crusts. South facing slopes in our northern sector are covered but and south facing slopes around the Central and South Valley are pretty darn bare.
Early morning temperatures are in the teens everywhere except Stanley is slightly warmer with 20 degrees at 6AM. Winds are out of the northwest, blowing 10 to 20mph with stronger gusts, especially along our southern mountains.
Mountain Weather Forecast:
Cloudy skies this morning should begin to break up by afternoon. We may see a few more snow showers in the mountains as this system leaves and a ridge of high pressure builds for the next few days.
Temperatures should reach 32 degrees on Baldy today, mid twenties at 10,000ft and rise into the mid thirties on the valley floor. Winds will continue to come from the northwest, but should decrease somewhat throughout the day.
Photos:
1. Cracking Wind Slabs on Titus Ridge
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| Reported Conditions |
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| Temperatures |
| Overnight Low |
11 |
17 |
12 |
| 6am Temperature |
12 |
17 |
13 |
| 24 hr Maximum |
22 |
25 |
36 |
| Winds |
| Current Winds |
7NW |
15NW |
- |
| 24 hr Average |
6 |
12 |
- |
| Maximum Gust |
23NW |
32NW |
- |
| Snow - Storm Interval # 17 |
| New Snow |
1" |
- |
- |
| Total Depth |
49" |
45" |
28" |
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