New wind slabs are going to be your biggest concern today. Light density snow is easily transported by the wind and can result in widespread windloading. You are MOST likely to find windslabs near ridgelines and on crossloaded slopes(think gullies and sub-ridges) in the upper elevations but today windslabs and new storm slabs are going to be even more widespread. A combination of new surface hoar growth mid week, light density snow from Wednesday and Thursday and over a foot of new snow will create some very touchy conditions on all steep slopes today. We received widespread reports of new snow instabilities yesterday and we have added another 8-10 inches in the lower elevations. Gusty South and Southwest winds combined with heavy precipitation intervals through the day will INCREASE the avalanche danger and increase your potential to trigger avalanches.
Look for wind affected areas, notice changes in the density of the snow surface and recognize red flags like cracking or collapsing under your skis or sleds. Today is the day to use good travel protocols, do not put more than one person on a slope at a time and avoid steep terrain.
We have been talking about our persistent weak layers all winter so far and why they are concerning. This is the storm we have been waiting for to give those layers a real test. We have been tracking these layers through the snowpack as well as how widely distributed they are throughout the terrain. The short version of the story is that we have a relatively complex snowpack with multiple weak layers that are widely distributed. We would need a crystal ball to accurately predict how these layers are going to react to the load of fresh and wind blown snow that is getting added right now. What we can accurately say is that this is the biggest storm cycle of the winter so far and the probability of natural and human triggered avalanches is going to be increasing as the snow piles up. Give the snowpack some time to adjust right now and avoid traveling on or near slopes that are steep enough to produce avalanches.
Let us know what you are seeing out there. It helps us paint a better picture of the current conditions across the West Central. It's easy to do, takes about 5 minutes and prompts you for pertinent snow and avalanche info. If you see an avalanche, note the direction the slope faces, relative elevation, depth of the crown and try to get a pic if possible. Your observations can make a difference. Submit avalanche observations Submit snowpack observations
Weather stations nearby are showing winds gusting into the teens right now with gusts into the mid twenties overnight. Later today SSW winds will increase. Lower elevation snow depths are already at 8 inches and increasing at about an inch per hour. Forecasts show that will also increase throughout the day. Yesterday the new light density snow was already showing signs of instability with some cracking and sluffing occurring. The clear, cold nights on Wednesday and Thursday added another thin layer of Surface Hoar into the equation.
All signs are pointing towards a natural avalanche cycle during this multi-day storm cycle. The timing is going to be tough to pin down but we have multiple avalanche problems that are waiting for a trigger. Smaller storm slabs and building wind slabs are the most likely scenario and you are most likely to trigger these. As these slabs grow, they are going to be breaking deep enough to bury a skier or snowmobiler. Larger, more destructive slides are going to be possible as well, these are going to be deep, involve 2-4 feet of dense snow and could kill a person or break trees.
|0600 temperature:||16 deg. F.|
|Max. temperature in the last 24 hours:||16 deg. F.|
|Average wind direction during the last 24 hours:||SW|
|Average wind speed during the last 24 hours:||NA mph|
|Maximum wind gust in the last 24 hours:||NA mph|
|New snowfall in the last 24 hours:||NA inches|
|Total snow depth:||39 inches|
...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 5 PM MST
* WHAT...Heavy snow. In the west-central and Boise mountains
additional snow accumulations of 1 to 2 feet in mountain valleys
with up to 3 feet over the mountains. In the Upper Weiser River
basin additional accumulations of 9 to 18 inches. Gusty winds
will accompany snowfall at times.
* WHERE...Upper Weiser River, West Central Mountains and Boise
* WHEN...Until 5 PM MST Tuesday. There will be notable breaks in
the intensity of snowfall Saturday night and again on Monday.
* IMPACTS...Travel will be very difficult to impossible.
This avalanche advisory is provided through a partnership between the Payette National Forest and the Payette Avalanche Center. This advisory covers the West Central Mountains between Hard Butte on the north and Council Mountain on the south. This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires at midnight on the posted day unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.