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West Slopes South - South of I-90 to Columbia River

Issued: 7:56 PM PST Tuesday, January 16, 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. 

Light to moderate snow Wednesday morning will add to the development of shallow wind slabs above treeline. Mitigate hazard by approaching lee slopes with caution and observing wind transported snow, which may extend into the near treeline zone in areas that see more snowfall than anticipated.

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Avalanche Problems for Wednesday

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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Avalanche Summary:

Across the west slopes of the Cascades, many locations near and above treeline received 2-4" of higher density snow Wednesday. Locally higher amounts were seen near Mt. Baker, especially above treeline. Moderate winds, with strong gusts, are locally transporting this shallow new snow around on Wednesday afternoon, most notably at Mt. Baker.

Recent snowfall sits on a firm crust at higher elevations and refreezing or still wet snow at lower elevations.

After 3 extraordinarily warm days of high pressure (Saturday-Monday), the snow from late last week is well consolidated and sits on a thin crust (Jan. 9) which may be found in the near treeline elevation band in most areas. A more supportable and thicker crust (Jan. 5) from rain or freezing rain is easily identifiable in the upper snowpack.

Below the 1/5 crust, observations continue to indicate a strong snowpack with no notable layers of concern.

Observations

North

Large natural and skier-triggered loose wet avalanches were reported on Sunday in the Twin Lakes area by Baker Pro Patrol and Hidden Lake Peak area via our public observations page.

Central

No recent observations

South

No recent observations

Forecast for Wednesday:

This discussion only applies to the Cascade West-Central and Cascade West-South zones.

Most areas in the central and south Cascades will see 2-4 hours of light to moderate rain and snow in the morning hours, with increasing moderate SE winds, and sharp warming during the late morning hours. Moderate to locally heavy rain will arrive in the evening.

Recent wet snow should be bonding well to firm surfaces in most areas. Recent gusty SW winds may have created shallow slabs in the above treeline areas. Additional snowfall Wednesday morning above 4500 feet will create shallow wind slabs as generally SE winds load lee slopes above and perhaps near treeline. Generally watch for active snow transport and navigate away from wind-loaded slopes, where small avalanches may be triggered on W-N-E aspects.

There will not be enough new snow to develop storm slab or wind slab below treeline. 

Loose wet avalanches will not be listed as a problem, but they are not out of the question with heavier rain arriving very late in the day.

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.