|
|
This is Blase Reardon of the Sawtooth National Forest Avalanche Center with your Backcountry Avalanche Advisory and Weather Forecast for Monday, February 8, 2010 at 7:30 am.
City of Ketchum (www.ketchumfire.org) & the Friends of the Sawtooth Avalanche Center bring you this advisory.
Special Announcement:
Last weekend’s Banff Mountain Film Festival and raffle raised over $8000 for the Friends of the Sawtooth Avalanche Center! A big thank you to the many local business and individuals that donated time or prizes, including Backwoods, The Elephant’s Perch, Galena Lodge, Ski Tech, Smith Optics, Sun Valley Heli Ski, Sun Valley Trekking and many other local businesses and individuals. We would also like to thank Sun Valley Brewing and Rolling in Dough for contributing refreshments. We would not be able to offer daily avalanche advisories or our avalanche education programs without such broad community support.
Bottom Line by Region:
 North Wood River Valley
|
|
The avalanche danger is estimated to be MODERATE on steep, mid- to upper elevation, shaded slopes. The snow structure in this region consists of weak, faceted snow buried beneath a 2-3 foot thick slab, with snow depths and stability mostly increasing as you head north. In these conditions, human-triggered avalanches are unlikely on most slopes, but any triggered avalanches have the potential to break out dangerously deep and wide. Because it’s difficult to determine which slopes are safe and which are not, be conservative when choosing slopes where you want to play or ride. Be especially wary of slopes steeper than about 35 degrees with shallow rocky areas and steep breakovers.
|
|
 South & Central Wood River Valley
|
|
The avalanche danger is estimated to be MODERATE on mid- to upper-elevation shaded slopes. In this region, a slab 1-2 feet thick sits on very weak, faceted snow. The likelihood of triggering an avalanche on this weak structure is gradually diminishing, but some slopes remain sensitive to a person’s weight. Be conservative when choosing slopes where you want to play or ride, and be wary of slopes steeper than about 30 degrees, especially those with shallow, rocky areas and steep breakovers.
|
|
|
Salmon Headwaters & Sawtooth Mountains
|
|
The avalanche danger is estimated to be MODERATE. A thick, hard slab sits on weak, sugary snow. You are unlikely to trigger an avalanche involving this structure, but any avalanche you do trigger has the potential to break out dangerously deep and wide. In the Salmon Headwaters, the slab is about 2-3 feet thick – just thick enough to for the weight of a person or snowmachine to collapse the underlying weak layer and trigger a slide, making for unpredictable avalanche conditions. Be conservative when choosing slopes where you want to play or ride, and be wary of slopes steeper than about 35 degrees with shallow rocky areas and steep breakovers. In the northern end of the Sawtooths, the weak faceted layer is buried 3-4 feet deep, and slopes where you could trigger an avalanche are becoming increasingly isolated.
|
|
|
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:
Several factors - the lack of recent loading from new snow or wind and the mostly unremarkable weather of the past ten days – seem to have allowed the snowpack to start stabilizing. We’ve had no human-triggered avalanches occur for over a week, only a couple of observations of natural avalanches in the past week, and isolated reports of collapses. In addition, stability test scores have been much more variable than two weeks ago. It’s taking mostly moderate to hard force to initiate a failure but we have had some reports of easy shears or collapses. The failures in stability and propagation tests have ranged from indistinct and ragged to energetic, pop-you-in-the-head-as-they-come-out wake-up calls. This is all evidence that the slopes where you could trigger an avalanche are becoming more isolated.
Keep in mind, however, that most people are only now starting to range beyond terrain with lower slope angles and few large start zones overhead, where we’ve been confined by avalanche conditions most of the past six weeks or so. When people are venturing into terrain with higher consequences and less certainty about stability, they are mostly nibbling at the edges. Thus, we really don’t know how yet isolated the instability is, or how sensitive many steeper slopes are to the weight of a person or snowmachine. The lack of recent human-triggered or natural avalanches is no proof that the snowpack is stable on steeper slopes, and neither are someone else’s tracks on a nearby slope. The simple fact is that so long as faceted snow and depth hoar remain intact near the base of the snowpack, the potential to trigger large, dangerous avalanches will continue to exist.
Since that’s the case for most slopes throughout our advisory area, we have to ride and play accordingly. That is, rely on travel practices that leave us the widest possible margins for error and minimize the penalties of any mistakes. Evaluate slopes for possible trigger points - shallow, rocky areas, steep breakovers or wind-loaded areas where avalanches are commonly triggered. Avoid slopes with terrain traps – cliffs or gullies that magnify the consequences of any slide. Expose only one person at a time, so you have the maximum number of people available for any search. Don’t take tracks on a slope as a demonstration of stability; they only show that it didn’t fail when someone rode or turned on that particular line at that time.
There’s little impressive weather in the forecast for the next week. That’s disappointing, insomuch as most of us reading this would like to have more fresh powder in which to ski or ride. But the break will likely serve as a kind of halftime for the winter, allowing the deeper snowpack to slowly, ever so slowly, strengthen. At the same time, long spells of dry weather typically weaken surface and near-surface snow, creating possible future weak layers.
Additional discussion: The direct sun of the past few days does not seem to be leading to many point releases on steeper, sun-exposed slopes. Cooler temperatures are helping to maintain the cohesion of the surface snow on these slopes. Loose snow avalanches will be unlikely on these slopes today as well, but not impossible. It’s worth keeping your avalanche eyeballs open for rollerballs and other signs of surface snow instability if you travel across or below steep slopes facing the sun, especially those with rockbands.
Current Conditions:
The ridge of high pressure that’s moved overhead brought a beautiful day to the mountains yesterday. Skies were mostly clear and winds at ridgelines were light and northerly. At sheltered sites, maximum temperatures climbed to freezing or above, but at more exposed locations the highs stayed in the mid-20s. A mild inversion developed overnight; temperatures early this morning are in the low teens at most upper elevation station but in the single digits in the Wood River Valley and about 10 below zero in the Stanley Basin. Despite the sun and strong diurnal temperature swings, mean temperatures have been cool – generally in the mid teens – and declining over the past few days. The cool temperatures are not promoting settlement of the snowpack; most stations are showing an inch or less in the past 24 hours.
Mountain Weather Forecast:
High pressure will continue to dominate our weather over the next few days. We can expect dry, cool conditions and partly cloudy or sunny skies today and tomorrow, with light and variable winds at ridgelines. Today’s highs are forecast to reach the mid 20s at upper elevations, and will probably creep above freezing at sheltered sites. Lows tonight are forecast to drop into the single digits at most elevations, though under clear skies another mild inversion is likely to develop. There's not much dramatic weather on the horizon, although a weak disturbance is forecast to move quickly through our area at the end of the week.
|
|
|
|
|
| Reported Conditions |
|
 |
|
 |
|
 |
| Temperatures |
| Overnight Low |
11 |
14 |
2 |
| 6am Temperature |
14 |
14 |
2 |
| 24 hr Maximum |
23 |
25 |
35 |
| Winds |
| Current Winds |
WSW9 |
calm |
- |
| 24 hr Average |
N7 |
N6 |
- |
| Maximum Gust |
N19 |
NE14 |
- |
| Snow - Storm Interval # 18 |
| Total Depth |
46" |
54" |
24" |
|
|
|
|
|
Announcements:
Accident reports can now be found on our new accident page:
http://www.sawtoothavalanche.com/accidents.php
The annual Warm Springs Winter Elk Closure is in place - this prohibits all travel on the Warm Springs south facing slopes from Wanderer's Way in Ketchum out to the West Fork.
A fund has been set up to help the Michael family through the Bald Mountain Rescue Fund, a non-profit established to assist ski community individuals and families after serious accidents. All contributions are tax-deductible and go directly to assist the family during this time of great loss. Please send all donations to:
Bald Mountain Rescue Fund/Michael Family
c/o Brian Barsotti
PO Box 370
Ketchum, ID 83340
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. Snow shoes or touring skis are recommended to get around over the snow.
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
Check http://www.wrh.noaa.gov/pih/ for the latest weather forecasts.
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.
|
|
|
|
|
|
