Payette Avalanche Center

Created:   12-16-2009

There is an Avalanche Watch in effect for the West Central mountains.

Bottom Line

Summary

The general avalanche danger is CONSIDERABLE for slopes near and at ridge-top. Over a foot and 
a half of new snow and winds in the past five days have created dangerous avalanche conditions 
on steep slopes underlain by weak, faceted snow. Unstable slabs are likely to be triggered by 
humans. On slopes lower down that are not wind affected the avalanche danger is MODERATE. This 
means human triggered avalanches are possible. We will issue our next advisory on Saturday, 
December 19th.
 
Avalanche Concern #1:
  	
Due to continuing snow and wind there is an Avalanche Watch in affect for the Payette and the 
Boise NF. If natural avalanches start occurring due to increased loading the avalanche danger 
will increase to HIGH. 

Avalanche Concern #2:
  	
New snow and wind have developed slabs overlaying weak faceted snow (sugar snow). These slabs are 
reactive to human weight. Travel yesterday produced widespread whumpfing and shooting cracks that 
traveled quite a distance away from initiation. Slope testing produced very easy shears with the 
potential to go to the ground. 

Recent Avalanche Activity:

We received a report of a remotely triggered avalanche within the ski area boundry at Brundage 
today. The ski area is not open for regular operations and there has not been any avalanche 
mitigation. Backcountry conditons exist at this time. Remember that you ski there at your own 
risk.  The slide was on a steep slope between North and Main Street. It was about two feet deep 
and 20 feet wide at the top. It was caused from by a party of backcountry skiers 200 ft. away. 
They reported hearing a whumph underneath their skin track that remotely triggered the slide on 
the slope. 

Current Conditions

Over a foot and a half of new snow has fallen in the past five days. Saturday morning at start of 
the storm a small fog crust was formed on the surface. This glazed over a weak layer of surface 
hoar on some northerly aspects and a mixture of sun crusts and near surface facets on more southerly 
aspects. Slope testing yesterday produced sheers both above and below this crust. The wind affected 
new snow falling on top of this has created a classic strong over weak situation, slab on top of a 
weak layer. This trap-door snow can be felt as you break trail on skis or on a sled. It feels 
"bottomless." All this needs is a trigger to cause avalanches. This may be new snow or wind loading 
but most likely is will be the added weight of a rider or skier. Please pay attention to the signs 
of instability. Recent avalanches, cracking and collapsing are Mother Nature's warning signs. 
Excellent terrain and snow stability evaluation skills and conservative decision-making are 
essential for safe travel in avalanche terrain today.

 
Mountain Weather

Snow is forecasted to continue through this evening with the potential to bring an additional 
3-9 inches by tomorrow. Temperatures will remain warm. Winds will continue from the south at 
5-15 mph. As the storm moves out there is a chance for showers through the rest of week as we 
remain in a moist flow.