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 wet warm storm arrived on Valentines Day 2/14 and formed the uppermost very strong rain crust in our snowpack. 

Strong southwest flow carried a strong front across the Northwest on Friday evening. At Mt Hood this caused strong southwest alpine winds, heavy, moist, dense new snow above about 4000 ft and wet snow or rain below about 4000 ft.

NWAC stations at Mt Hood have had about 1.5 ft of snow in the past 3 days.

Recent Observations

On Thursday, NWAC observer Laura Green reported that a sun crust had formed on solar slopes. She noted that several natural hard wind slab avalanches had occurred in White River Canyon above treeline on E-NE aspects with crown depths up to several feet. She also saw a 2-4 ft crown in Newton Canyon on a NE slope at about 6400 ft. These hard slab wind avalanches likely occurred on Wednesday.

Laura was out in Heather Canyon on Friday morning and found a reactive wind slab layer, giving moderate RP results at about 10 inches down in a pit on a NE slope at about 6450 ft. She was out later Friday on a tour in the East Fork area from 3500-5800 ft and found that the reactive wind slab layer was persisting there as well on a wind loaded slope about 10 inches down. Loose wet snow and pinwheels were seen below about 4000 ft.

The Meadows patrol reported large wind sculpted features in the alpine Sunday with large hard wind slabs on exposed lee slopes. Extensive explosive control failed to release these hard slabs. These hard slabs are not likely to release by human trigger but should give caution to those traveling in steep exposed terrain.

A report via the NWAC Observations page for Sunday for the Tom/Dick/Harry Mountain area also indicates stubborn wind slab with no avalanches.

Another report via the NWAC Observations page for Sunday for the Mirror Lake area reports a triggered storm slab.

The Meadows patrol on Monday reports no significant wind effects but widespread 8-12 in soft storm slab on most aspects, running at the interface with yesterday's snow, with some sympathetic releases.