Avalanche Forecast

A low pressure system is expected to move across the Washington Oregon border area on Tuesday. This is expected to cause the strongest winds, the most snow and possibly the most fluctuation in temperatures in the south Cascades.

With this next unusual and hard to predict incoming storm, so much recent snow, lack of knowledge of stabilizing of recent snow, and lack of knowledge of bonds to the Valentines Day crust, there is GREAT UNCERTAINTY in the avalanche forecasts at this time. This is a time to plan travel on lower angled terrain well away from avalanche paths or run out zones. Avoid large steep open slopes or terrain of consequence. Change your plans if weather and snow conditions are different than expected.

More than the usual zones are in this forecast due to the expected differences from south to north on Tuesday.

Alpine winds have recently been SW to W, with further mostly SW to W winds expected on Tuesday. Hence wind slab should be most likely on northwest to southeast aspects. But watch for firmer wind transported snow on other aspects especially in areas of complex terrain.

Most areas have experienced rapidly accumulating snowfall and temperature fluctuation the past couple days. Storm slab from this weather may not have stabilized. More areas of rapidly accumulating snowfall with fluctuating temperatures are expected on Tuesday.

Cornices won't be listed as an avalanche problem but avoid travel on ridges near where cornices may have formed and avoid steep slopes below cornices that may fail at any time.

Weather and Snowpack 

The most recent warm, wet storm arrived on Valentines Day 2/14 forming a strong rain crust, now buried 2-5 feet or more in most areas along the west slope Cascade zones. 

Strong southwest flow carried a strong front across the Northwest on Friday evening. Along the Cascade west slopes this caused strong southwest alpine winds, heavy, moist, dense new snow above about 3-4000 ft and wet snow or rain below about 3-4000 ft.

NWAC stations along the Cascade west slopes have had about 1.5-6 ft of snow in the past 3 days with the most at Mt Baker.

A region wide avalanche cycle was seen late Friday and Saturday, especially at Mt Baker, with some more avalanches on Sunday.

Recent Observations

North

Widespread 1-2 ft storm slabs and larger, 3-5 foot wind slabs were seen in the backcountry near Mt Baker on Saturday. A close call occurred on Mt Herman when a large wind slab was triggered, and partially burying two and fully burying one in a separate party at the base of the slide path after completing a run. It was a fortunate outcome with no significant injuries. The NWAC will compile a report and post on the website as soon as possible.

The recent storm snow is DEEP in the northwest zone and this should prompt a conservative approach to backcountry travel for several more days.

Central

NWAC observer Dallas Glass was in the Alpental Valley Saturday and reported that previous moist to wet snow was settling and less reactive. The earlier storm slab problem was rapidly improving in this zone. 

 

Wind slab, 1-2 feet, ski triggered Saturday 3/4, while ascending the ridge on Arrowhead Peak, east of Stevens Pass, 5500 ft elevation, SW aspect, no skier involvement. Photo: K. Johnson

Dallas was back in the western Alpental Valley Sunday, from 3000-5500 ft and noted a recent natural cycle occurred, likely early Sunday during heavy snow shower intensities. Numerous 6-8 inch storm slabs released in steep terrain near and below treeline. There is significant low density surface snow available for transport, so watch for increased winds over the next few days.

Several more triggered avalanches at Stevens and Snoqualmie were reported via the NWAC Observations page on Sunday.

South

NWAC observer Jeremy Allyn was in the Crystal Mountain backcountry Sunday and reported a favorable profile of the recent storm snow on N and W aspects. There was about 90 cm of snow on the Valentines crust. Hand and ski tests and test cornice drops did give results and wind effects were minimal in this area.

Here is a nice photo example of the cornice features, captured Sunday in similar terrain, near Crown Point by our good friend Seth Waterfall, thanks. 

Sensitive cornice and wind slab on Crown Point near Crystal Mountain on Sunday 3/5. Photo: Seth Waterfall