Avalanche Forecast

An incoming system will bring increasingly stormy weather with strong winds and moderate precipitation intensities along with rapid warming during the daylight hours.

This pattern will lead to a variety of avalanche problems, with the avalanche danger for each problem increasing as the day progresses. Travel in above treeline terrain is not recommended on Tuesday.

Plenty of new snow is available for transport by increasing moderate to strong winds re-distributing snow into the below-treeline terrain. Increasingly large and sensitive wind slabs will form and are likely to be very sensitive to triggering by late in the day on Sunday. Older wind slabs are still in the process of healing and may be more stubborn to trigger, but could yield avalanches that are larger than you expect. Identify and avoid wind loaded features such as snow drifts, slopes below cornices, and crossloaded slopes.

Storm slabs will become increasingly likely as warming and higher density snowfall create ideal conditions for slab formation. Expect slabs to be shallow, but avalanches may entrain significant recent lower density snowfall to form large avalanches.

A loose wet avalanche problem will develop as a problem during the afternoon hours as snowfall changes to rain at lower elevations where less snowfall has accumulated since the 01/17 crust. Natural loose wet avalanches are likely on steep, unsupported, or convex terrain up to 5000 ft, where enough recent snowfall has accumulated to create a problem. Avoid avalanche terrain as temperatures climb Tuesday afternoon. Be aware of the consequences of a small avalanche, particularly where cliffs, rocks, gullies, and creeks magnify the consequences.

Conditions will continue to deteriorate Tuesday night as further warming and heavy rain and higher elevation snow create very dangerous avalanche conditions anywhere significant recent snowfall has accumulated.

An active weather pattern from 1/18 onwards and continuing through Monday has deposited 1.5-2.5' of snow falling at temperatures generally in the upper 20's over the most recent 1/17 crust. Observations indicate the recent snow bonded well to the crust.

Recent light to moderate winds transported snow significantly in exposed terrain, particularly. West winds, seen earlier in the storm period, shifted to the South Sunday and became lighter and more variable. 

Poor visibility and dangerous travel conditions have made observations in above treeline terrain difficult to obtain. A high degree of uncertainty exists regarding the extent and sensitivity of wind slabs above treeline.

Below treeline lower snow totals have limited the development of avalanche problems.

Observations

On Monday morning, Mt Hood Meadows Pro Patrol reported 6" of new snow at 5300' and 13" at the top of the mountain that fell on Sunday night. Wind slabs up to 1' were found into near treeline terrain, with the larger releases triggerd by explosive.

On Sunday, Mt Hood Meadows Pro Patrol reported about 12" of snow over the 1/17 crust. Winds were transporting snow at all elevations. 

NWAC Pro Observer Laura Green was in the near treeline area of Heather Canyon on Friday. Recent storm snow had been redistributed by strong winds. Sensitive wind slabs were found on exposed slopes. Mostly shallow storm snow was found well bonded and not reactive to tests below treeline.