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.

Persistent slab is back in the forecast in the Northeast zone due to recent avalanches on this layer and due to recent reactive tests on this layer in this area.

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 and formed the uppermost strong rain crust in our snowpack in the Central East and Southeast Cascades while a thinner but prominent rain crust exists throughout the Washington Pass and Harts Pass areas.

Strong southwest flow carried a strong front across the Northwest on Friday evening. Along the Cascade east 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 east slopes have had about 8-12 in of snow in the past 3 days.

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

Recent Observations

North

A NCMG report for Friday for the Delancey area indicates heavy snow in the near and below treeline and 35-60 cm of storm snow on the Valentine's Day crust. Moderate planar shears were found in recent storm snow layers. New storm slabs were forming and ski tests were producing storm slab and loose dry releases. Whumpfing and cracking was seen above 6600 ft.

There was a skier triggered storm slab avalanche involvement Saturday in the Cedar Creek drainage resulting in a full burial and beacon recovery. The full details are not known at this time, but the party member is expected to be fine, another fortunate outcome. Investigations on scene Sunday indicate that this slide released on the Valentine's crust buried nearly 3 feet in this area. The avalanche was triggered well below ridgeline, at about 6600 feet on a north aspect.

NWAC observer Jeff Ward was in the Willow and Cedar drainages on Sunday and found reactive tests on the Valentine's Day at 85 cm. Whoomping was experienced while traveling on an up track. Numerous avalanches up to size 3 were noted on all aspects near and above treeline from Friday night. He also reported that the Valentine's Day crust was found 50 cm down at Hart's Pass.

Jeff was out again on Monday in the Cutthroat drainage and found a generally right side up snowpack with no significant results from ski tests. The thinner crust from 2/17 was spotty and generally not an issue. The Valentine's Day crust here at 125 cm was not reactive so note the varying results on this layer in different areas.

Central

There were numerous avalanche involvements Saturday 3/4 in this zone. We do not have adequate information at this time, other than to say, there was a fatality to a snowmobiler in the Gallagher Head Lake area, north of the Salmon La Sac area where 2 snowmobilers were buried by an avalanche. This information is likely to change as we investigate the accident. Check the NWAC Observations page for more details.

South

No recent observations.