Avalanche Forecast Olympics

Tuesday 22nd January 2019

Avalanche Danger Ratings Tue 22nd Jan 6:03PM Danger Ratings Alpine: Below Threshold Danger Ratings Treeline: Below Threshold Danger Ratings Below Treeline: Below Threshold

Forecaster: Robert Hahn

Date Issued:

Valid Until:

The Bottom Line: Avalanche danger is likely to peak overnight, but avalanche danger created due to recent wind and snow and rain will linger and gradually decrease through the day. Be patient and give very recently formed slabs time to settle. If you head out, please be aware that our snowpack information is very limited at this time.

Snow and Avalanche Discussion

Temperatures and winds were increasing on Tuesday, but moisture arrived more slowly than anticipated. However, the storm isn’t over and strong winds and light to moderate precipitation are still forecast for Hurricane Ridge. Snow levels are expected to peak around 6500 ft later Tuesday night and this high snow level should confine to the uppermost elevations at Hurricane Ridge on Wednesday.

Our received our first observation in over a month from the Olympic mountains illustrated multiple strong crust layers extending to near the surface and wind-drifted surface snow near treeline, with little to no snow below 4000 ft. We will not try to extrapolate this observation to other parts of the range as snowpacks may differ widely.

Right now we are forecasting without specific snowpack and avalanche observations from the Hurricane Ridge area due to the government shutdown. If you travel to the Olympic Mountains, please help your local forecast by submitting an observation. We haven’t received updated snowpack information for one month.

Regional Synopsis

January 20, 2019

The recent weather pattern of lower accumulation storms (by NW standards) and longer stretches of calm weather should continue as we move into late January. Since January 17th, incremental snow accumulations punctuated with rising freezing levels favored the south and eastern parts of the region. Storm instabilities have risen with storms and gradually subsided.

A storm slab at Mt Baker.

New Snow Problems

Storms over the past week have brought a range of layers from rain crusts, to heavy moist snow, to stiff drifts, to light dry powder. Some storm days, like the 18-19th, saw reactive, but very short-lived avalanches caused by heavy precipitation and wind. Even the longer-lasting avalanche problems, wind slabs, haven't persisted for more than a few days. Where the recent snow is stressing underlying weak layers, more dangerous avalanche conditions have prevailed.

Surface hoar in the East Central zone

Old Snow Problems

Persistent weak layers (PWLs) have been a constant in the eastern zones of the Cascades this winter. As usual, they have been much less problematic at the Passes and west of the Cascade Crest. The latest PWL is a layer of surface hoar, buried around January 17th and found generally east of the Cascade Crest. Buried surface hoar is an active weak layer in the eastern zones and can be found to a limited extent on the eastern edge of the Stevens and Snoqualmie Pass zones. There few, if any, avalanches have been reported on the buried surface hoar. It may be most problematic in open, wind-sheltered terrain, especially well above the valley floor.

You are most likely to find other layers of old weak snow the further you move east from the Cascade crest. Here snowpacks are shallower, more variable, and generally weaker. In some locations, weak snow near the ground can still be found. These basal facets have hung around all season. Digging profiles and using snowpack tests is the best way to gain information about these old persistent weak layers. However, snowpack tests are just one piece of the puzzle. Your terrain decisions shouldn't hinge on any given test result. Because of the size of our forecast zones and the variability in the snowpack, it's important to make snow observations as you travel. We’ll keep watching these old layers, but let us know what you see while you are in the mountains.

Weather Forecast

Wed 23rd Jan 09:33 - Dennis D'Amico

Weather Synopsis for Wednesday & Thursday

A strong frontal system passed through the region Tuesday night, leaving post-frontal showers mainly for the west slopes of the Cascades and Mt. Hood area this morning. Areas along the west slopes of the Cascades/Mt. Hood picked up 6-12+ inches before a switch to rain at 4000 ft in the north, 5000-5500 ft in the central and south Washington Cascades and 6000 ft at Mt. Hood. Strong westerlies seen from Stevens Pass and south will come down later this morning, except at Mt. Hood where strong westerlies will linger through much of the day. 

Showers will diminish through this afternoon, becoming isolated in the evening. A strong upper level ridge will rebuild offshore Wednesday night and Thursday with dry conditions forecast tomorrow. Some low-level moisture/clouds will likely to be trapped along the west slopes of the Cascades Thursday with sunnier skies forecast along the east slopes of the Cascades. Freezing levels will be on the rise in general, but will make for a tricky forecast with warm air struggling to make inroads for the north and central Cascades. Higher freezing levels look like a better bet over the Olymipcs and Mt. Hood area.  

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