We had a mixed bag of snow conditions in the mountains this week and we are adding some light freezing temperatures with some moderate accumulations today. Generally, the avalanche danger is Low throughout the West Central, but you will want to pay attention to the new snow accumulation and the way that it is sticking to the old snow surface below. The layer of Surface Hoar and Near Surface Facets that we had growing earlier this week on the snow surface was mostly wiped out by the warm temperatures later in the week. Our model forecasts are calling for 4-6 inches over the next 10-12 hours maybe a little more in the highest elevations in the area. As the new snow accumulates today the potential for shallow soft slabs in this layer will increase. Watch for increasing avalanche hazard tomorrow if we get the snow that is forecasted.
Persistent Slab avalanches can be triggered days to weeks after the last storm.They often propagate across and beyond terrain features that would otherwise confine Wind and Storm Slab avalanches. In some cases they can be triggered remotely, from low-angle terrain or adjacent slopes. Give yourself a wide safety buffer to address the uncertainty.
Triggering a slab due to this weak layer has become more difficult over the last few days with the heat, but I would not let my guard down, We are still finding this weak layer in upper elevation wind protected terrain. Pit results and stability testing are pointing toward less likelihood of triggering, but if triggered we are still talking about a potentially unsurvivable hard slab avalanche. Take the time to carefully assess terrain choices on the north half of the compass today. Especially areas where the snow cover is thinner which allows the buried surface hoar to be closer to the surface, and in turn more reactive---especially for snowmachines. This is the same layer that was the cause of the fatal avalanche on January 31st. A persistent weak layer such as this is a low probablility, but HIGH CONSEQUENCE scenario.
Today we are going to see relatively stable temperatures throughout the mountains but as the day progresses, a warm front will be passing by increasing temperatures tonight and tomorrow. The possiblity of wet/loose avalanches will increase this afternoon in the lower elevations as the snow turns to rain and temperatures climb. Rain on snow often results in larger wet/loose slides in the steeper river canyons and along roadways.
Thanks to everyone that came out last night for the FPAC fundraiser. We didn't have our normal loot pile this year but we still had a great evening. Thanks to all the companies and local businesses that did support us with their generous donations this year, especially Salmon River Brewery for donating the beer and tap system. Little Ski Hill proved to be a great venue and we are looking forward to using it again next year, thanks Colby and crew, you guys rock! Thanks to the FPAC board members for pouring beers, flipping burgers and sorting out the giveaway items, you guys are great! Thanks also to the MC and assistant MC for making it fun! A big thanks to Dave Looney for pulling the trigger on the Dynafit Skis last night, they almost didn't get bought...
Our snowpack looked like a melting snowcone this week. Short periods of freezing temperatures have increased the strength of the snowpack but we are still harboring some weak layers below that. The new snow that is falling today and tonight may have trouble bonding to the variable surface that we found yesterday across much of our area, so we may have some new shallow instablities to deal with in the storm snow layer. Pit results through the last few days have showed a shallow snowpack instability on a density change about 10-12 inches down. This layer has been moderately reactive but lacks the potential for propagation given the amount of saturated snow above it. We are still finding the layer of buried surface hoar preserved down around the 2-3 foot level and this is the layer that should be in the back of your mind if you are travelling in steep, sheltered, wind protected, shady terrain. It is a low proabability/high consequence layer that is very hard to forecast for with a high degree of certainty right now. We will be back out this week looking for the results of the warmup on this layer in areas that we found it over the last 3 weeks.
The good news is that it is snowing, the bad news is temperatures will be warming through the next 48 hours. Storm totals today should be in the 4-6 inch range in the mountains. The upper elevations can expect additional snowfall tonight with snowlines rising towards 6500 feet. Lower elevations will unfortunately be getting mostly rain by this afternoon and tonight.
NWS Short term forecast:WARM FRONT MOVING THROUGH THE REGION THIS MORNING BRINGING GENERALLY RAIN BELOW ABOUT 4500 FEET. ACCUMULATIONS OF AROUND AN INCH ARE SO FAR BEING REPORTED IN MCCALL AND AT THE LOWER ELEVATIONS AROUND TAMARACK. UP TO 2 INCHES OF SNOW REPORTED AT BRUNDAGE. SNOW LEVEL WILL ONLY RISE THROUGH THE DAY AS THE WARM FRONT LIFTS TO THE EAST AND NORTHEAST. BY THIS AFTERNOON EXPECTING SNOW LEVELS AROUND 6500 FEET IN THE FAR NORTH NEAR MCCALL TO OVER 8000 FEET NEAR THE NEVADA/IDAHO/OREGON BORDER. PRECIPITATION WILL BE ON THE DECREASE LATER THIS AFTERNOON WITH ONLY LINGERING SHOWERS ACROSS THE MOUNTAINS TONIGHT AND EARLY MONDAY. WARM CONDITIONS ARE EXPECTED THROUGH MONDAY WITH TEMPERATURES GENERALLY 5 TO 10 DEGREES ABOVE NORMAL AS THE WARM FRONT KICKS OUT AND THE UPPER RIDGE BUILDS BACK INTO THE REGION.
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.