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Stevens Pass

Issued: 7:58 PM PST Monday, February 5, 2018
by Robert Hahn

NWAC avalanche forecasts apply to backcountry avalanche terrain in the Olympics, Washington Cascades and Mt Hood area. These forecasts do not apply to developed ski areas, avalanche terrain affecting highways and higher terrain on the volcanic peaks above the Cascade crest level. 

Watch for highly variable and unpredictable shallow wind slabs near and above treeline. Travel cautiously in areas receiving recent snow. Large and destructive Glide avalanches and cornice falls may still be a hazard where rain has saturated old snow. Avoid terrain with open cracks in the snow and overhung cornices near ridge lines.

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Avalanche Problems for Tuesday

Wind Slabi

Wind slabs can take up to a week to stabilize. They are confined to lee and cross-loaded terrain features and can be avoided by sticking to sheltered or wind scoured areas.

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Glidei

Glide avalanches occur when water lubricates the interface between the snowpack and the ground. These avalanches are difficult to predict and best managed by avoiding terrain below glide cracks.

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Avalanche Summary:

Post-frontal showers continued on a cooling trend behind the front on Sunday night into Monday with NWAC stations from Snoqualmie Pass northward receiving 1-3" of snow in the near treeline band, with less below or to the south. Winds were reported to be gusty and variable in the Cascades, so expect this new snow to have been redistributed near and above treeline, particularly from Snoqualmie Pass northward.

Recent snow sits on wet snow that has in some cases refrozen into a crust of varying supportability and in other cases where snow immediately insulated the crust, the older snow is still wet. The wet snow was created by a very moist system that arrived over the weekend, bringing rain totals in the 1.8-3.5" range from Saturday night through Monday morning and creating wet snow up to 6500 feet. Crystal was rainshadowed and only picked up .45" during this time frame.

The above treeline terrain at Mt. Baker is likely an exception and may have seen significant snow during this storm and deep snow conditions significant wind slabs may still be present here.

A widespread natural Loose Wet avalanche cycle occurred Friday through Sunday. Observers reported both natural cornice falls and glide avalanches. We’ve received minimal reports of wet slab avalanches. Poor visibility and stormy conditions have limited observations at higher elevations.

Observations

North

Mt. Baker Ski Patrol reported not much avalanche activity since Saturday. A few inches of new snow now sits on top of large, wet rounded grains.

Mt Baker Ski Patrol reported rain to 5000 feet Friday and Saturday with a natural loose wet avalanche cycle occurring in the adjacent backcountry terrain. They observed debris from larger slab avalanches on the Shuksan Arm and Mt Herman as well as cornice fall near Table Mountain.

NWAC Forecaster, Dallas Glass, was greeting backcountry travelers at the Heather Meadows trail head on Saturday and reported snow lines wavering between Heather Meadows (4,200ft) and ridge tops. Dallas observed numerous wet loose avalanches in the Bagley Lakes area.

NWAC pro-observer Lee Lazzara traveled in the Canyon Creek area Thursday. Lee found 15-24 inches of recent snow over the 1/29 crust. Wind Slabs were noted in terrain near ridgeline but poor visibility limited observations near treeline.

Stevens Pass

NWAC Avalanche Forecasters and observers noted numerous natural wet loose avalanches on all aspects Friday and Saturday. These avalanches ranged from small to large, with some travelling 1000 vertical feet.

Snoqualmie Pass

On Sunday NWAC observer, Matt Schonwald, found a saturated snowpack with rain water more than 2 feet below the snow surface. Alpental Ski Patrol reported audible cornices collapses along ridges in the Alpental Valley on Saturday. Both patrol and NWAC observers reported Glide avalanches, visible glide cracks, and many wet loose avalanches

South

Crystal Mountain Ski Patrol reported seeing debris from a widespread natural loose wet avalanche cycle. The avalanches were large and ran far into the runouts. Cornices are sagging, but many didn't release during the recent warmup. The snow surface had refrozen by Monday morning and conditions were softening on solar aspects.

Crystal Mountain Ski Patrol reported skier triggered wet loose avalanches in terrain with an uncompacted, backcountry-like snow on Saturday.

Forecast for Tuesday:

A cooling trend beginning Sunday night will continue through the day on Tuesday with decreasing winds and decreasing additional new rain or snow loading expected, heaviest in convergence possible near Stevens or Snoqualmie passes.

Wind slabs will be present above treeline and may creep into the near treeline in particularly gusty locations. Due to very modest snow amounts expect wind slabs to be possible and generally small in most locations. However, due to uncertainty and lack of observations, anticipate that wind slabs may be large above treeline. The gusty and variable winds have created wind slabs on all aspects in some locations, so don't assume that your normal routes will be free from wind-loading. Also, where no new snow has fallen since the weekend's rain event, don't expect wind slabs to be a problem, such as in the Crystal Backcountry.

Near and below treeline, glide Avalanches and cornice falls could be big enough to bury or kill you.  Both of these types of avalanches form in specific types of terrain. The best way to stay safe is to avoid areas where these avalanches form and release. Watch out for slopes with visible glide cracks or where known rock slabs lie under the snowpack. Give yourself an extra wide margin of safety near ridges that could hold cornices, and avoid slopes with cornices overhead. Be aware that water running at the bottom of the snowpack can trigger a glide avalanche long after the rainfall and with significant rainfall over the weekend, we're leaving the possibility in the forecast for another day.

The loose wet avalanche cycle has largely played itself out as cooler temperatures are making the snow firmer. While these avalanches may be the smallest and most predictable of today’s avalanche flavors, they could still be big enough to injure you. Avoid traveling through or above terrain that could increase the consequences of being caught in an avalanches such as or cliffs, gullies, or rocky slopes.

No Corresponding Mountain Weather Forecast Available

USE AT YOUR OWN RISK

This Backcountry Avalanche Forecast is provided in conjunction with the US Forest Service, and is intended for personal and recreational purposes only. Safe backcountry travel requires preparation and planning, and this information may be used for planning purposes but does not provide all the information necessary for backcountry travel. Advanced avalanche education is strongly encouraged.

The user acknowledges that it is impossible to accurately predict natural events such as avalanches in every instance, and the accuracy or reliability of the data provided here is not guaranteed in any way. This forecast describes general avalanche conditions and local variations will always occur. This forecast expires 24 hours after the posted time unless noted otherwise.