The storm system yesterday dropped up to 10" of new snow and the new load has created unstable storm slabs on slopes >35 degrees. In addition, moderate westerly winds have drifted the light-density new snow onto leeward terrain features and built reactive wind slabs 1-2' deep on N-E-S aspects near ridgeline and cross-load ribs and gullies mid-slope. Avoid slopes >30 degrees with recent wind deposits and watch for loose dry avalanches on steep >35 degree terrain.
Today's forecast is sponsored by Wallowa County Gamblers Snowmobile Club
Yesterday, the Blue Mountans received up to 10" of new snow on top of the 7" that have fallen since Sunday, 2/26. This new snow is not bonding well to the underlying old snow surface and has created unstable conditions on slopes > 30 degrees. The best strategy for the next few days is to avoid avalanche terrain - stay off and out from under slopes > 30 degrees.
The 10" of new snow that come in with yesterday's storm is very light density and has been easily transported by the wind. Yesterday and overnight the winds have been mostly out of the west in the teens and gusting 20's near ridgeline. The moderate winds have created wind-affected snow and riders are likely to find 1-2' reactive wind slabs on steep (>35 degree) on N-E-S aspects near ridgeline and on cross-loaded terrain features mid-slope. Look for smooth rounded pillows below ridgeline and on the leeward side of ribs and gully features mid-slope. It is best for the next few days to avoid steep alpine terrain where reactive wind slabs may lurk.
Over the last few weeks the buried persistent weak layers in the upper and lower snowpack have been mostly unreactive to human-triggering and have been gaining strength. I want to stress that pesistent grain types still exist throughout our snowpack. In particular, we have several facet/crust combos in the upper snowpack (top 3 feet) that remain a concern. Yesterday, up at Spout Springs, I found a layer of weaker snow below the 2/26 melt-freeze crust that was reactive in my snowpack tests just over a foot down. See my observation report HERE.
There are also still some pockets of preserved and buried surface hoar. As our favorite astrologist Carl Sagan said, "The absence of evidence is not evidence of absence." Be sure to evaluate the snowpack on any slope >35 degrees for buried persistent weak layers. If you see poor structure in the upper snowpack - namely strong over weak - then be sure to test those suspect layers for reactivity. Also, it is good protocol to avoid possible trigger points in the terrain like convex rollovers, unsupported slopes above and below cliff bands, slopes punctuated with rocks, and areas in the terrain where the snowpack is shallow, <4' deep.
Protected and Sheltered Slopes Below Treeline
The snow quality on more protected and sheltered terrain is incredible right now. The cold temperatures and constant scud storms have left up to 18" of lovely light density snow in the Blue Mountains. This is the place to find the best snow quality and stability. There really isn't a good reason to go above treeline - unless you like to punish yourself with variable and more unstable conditions.
Wind Slabs
While great conditions are to be had below treeline, the situation changes dramatically as you move to treeline and above. If you are moving above treeline, then a new terrain mindset is warranted. It will be challenging to negotiate and avoid the wind slab hazard at upper elevations. The winds have been variable the last 36 hours and have moved the light density snow around considerably. You could easily find pockets of wind slab on the southside of gully and rib features as on the northside. The uncertainty of where pockets of wind slab exist will be high for the next several days. Attempting to "thread the needle" is not a good way to move through the mountains and stay safe. Again, the best snow quality will be found below treeline.
Persistent Slabs
Over the last few weeks the buried persistent weak layers in the upper and lower snowpack have been mostly unreactive to human-triggering and have been gaining strength. I want to stress that pesistent grain types still exist throughout our snowpack. In particular, we have several facet/crust combos in the upper snowpack (top 3 feet) that remain a concern. There are also still some pockets of preserved and buried surface hoar. As our favorite astrologist Carl Sagan said, "The absence of evidence is not evidence of absence." The load from the new storm snow may be enough to reactivate these more deeply buried weak layers. Be sure to evaluate the snowpack on any slope >30 degrees for buried persistent weak layers. If you see poor structure in the upper snowpack - namely strong over weak - then be sure to test those suspect layers for reactivity. Also, it is good protocol to avoid possible trigger points in the terrain like convex rollovers, unsupported slopes above and below cliff bands, slopes punctuated with rocks, and areas in the terrain where the snowpack is shallow, <4' deep.
Loose Dry Avalances
We have 12-18" of super light snow that is not bonding well to any slope that has an old melt-freeze crust or wind scab. In particular, it will be good to avoid steep (>35 degree) terrain where triggering a point release or sluff may get that new snow moving quickly down the slope, taking you off your feet or sled, and pushing you into terrain traps or stationary obstacles.
