menu
print

Snoqualmie Pass

Special Avalanche Bulletin i

Issued: Mon, May 22, 2017 at 2:58 PM PST
Expires: Tue, May 23, 2017 at 6:00 PM PST

Issued: 2:58 PM PST Monday, May 22, 2017
by Dennis D'Amico

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.

NWAC Spring Forecast Schedule

The NWAC issued daily mountain weather and avalanche forecasts through Saturday, April 15th. Mountain weather and avalanche forecasts were issued during the spring transition April 20-22nd and April 27-29th. Weekend outlooks will be issued Thursdays, May 4th, 11th, 18th and 25th.

Special advisories, watches and warnings will be issued throughout the spring for unusual or dangerous avalanche conditions. You can find out what constitutes a special advisory, watch or warning here.

Watch for the lack of an overnight refreeze of surface snow, wet snow deeper than boot top and initial pinwheels and initial small loose wet snow avalanches that indicate an increasing loose wet avalanche danger. It is always a good plan to be away from avalanche terrain by the warmest midday and afternoon hours. Careful snowpack evaluation and cautious routefinding will be essential through Tuesday.

Snowpack Analysis:

Recent Weather

The first half of last week was unusually cool with significant accumulating snowfall in the Olympics and Cascades, with the highest snowfall totals on or near the volcanoes. Strong upper level ridging over the last few days has allowed a steady increase in freezing levels over the weekend peaking to around 12000-13000 feet on Monday. Overnight temperatures have been well above freezing at NWAC weather stations the last few nights.  

Recent Avalanche Observations

Loose wet slides on steeper slopes have been the story over the last few days as expected. Larger slides were observed in areas that received more recent snowfall last week. 

Small-large natural loose wet avalanche activity on the Interglacier, Mt. Rainier on Saturday 5-20-17. More loose wet activity was observed on Sunday.

Photo by Richard So.

Detailed Forecast for Tuesday:

Weather Outlook

Strong upper level ridging Monday and Tuesday will continue the recent warmth with freezing levels holding steady in the 11,000-14,000 ft range along with mostly sunny days and mostly clear nights. However, a deep low pressure system in the NE Pacific will approach the B.C. coast Monday night and shift the ridge inland on Tuesday, allowing for some cooling in the Olympics and north Cascades during the day on Tuesday. Crest level westerly winds are forecast to increase during the day Tuesday for all areas. As the upper low passes inland and to our north Tuesday night, much cooler air will push into the region along with marine clouds along the west slopes of the Cascades and Olympics and bring about a few light showers.    

Avalanche forecast and travel advice

Many steeper aspects have already produced loose wet avalanches over the last few days. On steeper slopes that have not released yet, the loose wet avalanche potential remains highest during the warmer, sunny daytime hours. Large or very large loose wet snow avalanches are likely on the volcanoes where there has been the most recent snow. Remember that even small, loose wet snow avalanches can be powerful and dangerous especially around terrain traps.

Watch for the lack of an overnight refreeze of surface snow, wet snow deeper than boot top and initial pinwheels and initial small loose wet snow avalanches that indicate an increasing loose wet avalanche danger. It is always a good plan to be away from avalanche terrain by the warmest midday and afternoon hours. Careful snowpack evaluation and cautious routefinding will be essential through Tuesday.

Other Types of Avalanche Problems:

Nearby glide cracks and extensive loose wet avalanches can indicate that wet slab avalanches are possible.

Cornices should be starting to melt back but may remain unstable during prolonged warmer weather. Avoid potential cornices which can break well back from the edge along ridges and avoid traveling in areas underneath cornices on ridges above. See our blog post about cornices here.

Don't linger and move one a time if you decide to travel under rock slabs holding snow where sudden glide avalanches can release.

NWAC forecasts and statements do not apply to where conditions are likely to be more dangerous above the crest level on the volcanoes.

No Corresponding Mountain Weather Forecast Available