|
|
This is Chris Lundy of the Sawtooth National Forest Avalanche Center with your Backcountry Avalanche Advisory and Weather Forecast for Thursday, March 11, 2010 at 7:30 am.
Idaho Department of Parks & Recreation in partnership with Idaho's Snowmobile License Plate Program & the Friends of the Sawtooth Avalanche Center bring you this advisory.
Bottom Line by Region:
 North Wood River Valley
|
|
The avalanche danger is estimated to MODERATE. Areas of CONSIDERABLE danger exist on some steep, shaded slopes at mid to upper elevations. Dangerous avalanche conditions continue to be present where surface hoar and faceted snow are buried 12-18 inches deep. This layering is most widespread in the more remote areas of the Smoky Mountains typically accessed by snowmobile, including the Baker Creek drainage, where numerous avalanches have been triggered during the past week. In these regions, shaded slopes steeper than 35 degrees should be avoided. In the North Wood River Valley and Galena Summit area, the distribution of the weak layer is less common and steep slopes should be carefully evaluated. Watch for wet slides on sunny aspects with warming temperatures this afternoon.
|
|
 South & Central Wood River Valley
|
|
The avalanche danger is estimated to CONSIDERABLE on steep, shaded slopes at mid to upper elevations. Dangerous avalanche conditions continue to exist where 10 inches or more of recent snow has accumulated on layers of buried surface hoar and facets. Obvious signs of instability – such as cracking and collapsing – continue to be reported in this region. Shaded slopes steeper than 35 degrees should be avoided where the weak layer is found buried more than 10-12 inches deep. Watch for wet slides on sunny aspects with warming temperatures this afternoon.
|
|
|
Salmon Headwaters & Sawtooth Mountains
|
|
In the Salmon Headwaters, the avalanche danger is estimated to CONSIDERABLE on steep, shaded slopes at mid to upper elevations. Dangerous avalanche conditions continue to exist due to layers of surface hoar and facets buried 12-18 inches deep. Obvious signs of instability may be decreasing as time goes by, but triggering a slide on shaded slopes steeper than 35 degrees remains likely and these areas should be avoided.
In the Sawtooths, the avalanche danger is estimated to be MODERATE. Although the snowpack is more stable in this region, surface hoar buried a foot deep has surprised several folks over the past few weeks and steep slopes should be evaluated for the presence of this layer.
Watch for wet slides on sunny aspects with warming temperatures this afternoon.
|
|
|
Soldier Mountains
|
We provide the Bottom Line for the Soldier Mountains on Friday, Saturday, and Sundays at 7:30am. Please continue to read the full advisory as the information may be applicable to this region.
|
|
Primary Avalanche Concern:
A large portion of our forecast region continues to be plagued by buried weak layers of facets and surface hoar that were overloaded by snowfall a week ago. The most dangerous conditions exist in the Salmon Headwaters and western Smoky Mountains, including the Baker Creek drainage as well as the Soldier area. A widespread layer of surface hoar that was buried back in mid February is now about 18 inches down and has resulted in a number of natural and human triggered avalanches during the past week. Most recently, my partner and I triggered three avalanches in Baker Creek on Tuesday with the added weight of only a small cornice rolling down a slope.
An unstable snowpack is also prevalent in much of the South and Central Valley. Yesterday on Triple Peak, I received several collapses as well as shooting cracks as soon as I wrapped onto a shady aspect. Digging down through the surface layers gave a quick picture of the instability. I found 10 inches of recent snow sitting on a layer of sugary facets delicately sandwiching an obvious stripe of surface hoar. This potent cocktail of fragile snow grains produced extremely easy and clean shears during stability tests.
Decision making in these regions is relatively easy right now – the best approach is to avoid shaded slopes steeper than 35 degrees. Warming temperatures and sunshine today may increase the sensitivity of these buried weak layers.
Somehow the North Wood River Valley and Galena Summit area ended up in the semi-happy medium between the two problems I just described. I could explain to you my theory of how this happened, but I’m not sure I’d finish in time for tomorrow’s advisory. Suffice it to say that the weak layer can be found in portions of this region, but it is not as widespread and hasn’t produced such clearly unstable conditions. In many ways this is a trickier situation - it means fewer unstable slopes, but it’s also easier to let your guard down and eventually get fooled. To recreate on steeper slopes requires evaluating the snowpack stability on a slope-by-slope basis, which can be tiring for some who’d just rather be skiing or riding. If you fall into this category, slopes less steep than 35 degrees or sunny aspects provide good alternatives.
Secondary Avalanche Concern:
With warmer temperatures and plenty of sunshine today, wet slides will become a problem by this afternoon, especially where recent snowfall has accumulated on slick crusts. Sunny slopes will likely provide some great sliding conditions early today, but be ready to head to shadier terrain if things start coming unglued.
Current Conditions:
Temperatures yesterday remained cool with upper elevation sites only reaching the mid teens to low 20s. This morning, they’ve plummeted even further with single digits in the mountains and a temperature of only 10 degrees in Ketchum. At 6am, the temperature was -6 in Stanley and still dropping. Upper elevation winds are currently averaging 5-15 mph from the west.
Sliding and riding conditions remain very good on many aspects. Sheltered and shady slopes continue to offer settled powder, except at lower elevations in the South and Central Valley where a breakable crust exists. Many solar aspects are providing supportable dust on crust or corn-like conditions.
Mountain Weather Forecast:
High pressure will dominate today and tomorrow, bringing sunny skies and warming temperatures. Although temperatures are starting out on the chilly side, they will eventually climb into the mid 20s at upper elevations and the mid 30s on the valley floor. Even warmer temps appear to be on tap for tomorrow. Ridgeline winds should continue to blow in the 10-15 mph range from a westerly direction.
|
|
|
|
|
| Reported Conditions |
|
 |
|
 |
|
 |
| Temperatures |
| Overnight Low |
5 |
11 |
9 |
| 6am Temperature |
5 |
12 |
10 |
| 24 hr Maximum |
17 |
17 |
35 |
| Winds |
| Current Winds |
14 W |
6 W |
- |
| 24 hr Average |
11 NW |
7 N |
- |
| Maximum Gust |
24 NW |
17N |
- |
| Snow - Storm Interval # 23 |
| Total Depth |
52" |
59" |
22" |
|
|
|
|
|
Announcements:
The annual Warm Springs Winter Elk Closure is in place - this prohibits all travel on south facing slopes in the Warm Springs drainage from Wanderer's Way in Ketchum out to the West Fork.
The Avalanche Rescue Training Park is located in the Festival Meadows, next to Our Lady of the Snows Catholic Church on Sun Valley Road. It is free with easy instructions on the control panel and open all day. All you need is a beacon and probe to practice your skills.
The beacon practice area on Baldy is now located near the trees in the center of Christmas Ridge.
To find out where Sun Valley Heli Skiing plans to operate on any given day, call their status line at 622-2999.
Your observations are invaluable! They help us produce more accurate advisories which in turn helps you. If you get into the backcountry, let us know what you see out there - especially if you see or trigger any avalanches. Call (208)622-0099 or fill out the observer form on our website: http://www.sawtoothavalanche.com/submit_observation.php
For Idaho road closures check http://511.idaho.gov
For a recording of this advisory, call the Avalanche Hotline - (208)622-8027.
This information only applies to the backcountry and does not apply to highway programs or operating ski areas. Changing conditions and local variations may occur.
|
|
|
|
|
|
