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Avalanche Forecast

Archived

Dec 31st, 2018–Jan 2nd, 2019

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Snoqualmie Pass.

The bottom line: Happy New Year! New Year’s Day should be a beautiful day to be in the mountains. Don’t let the nice weather fool you. You may still trigger avalanches in wind loaded areas. Look for and avoid wind drifts in unusual locations like lower on the slope and the sides of gullies.

Avalanche and Snowpack Discussion

The only avalanche activity reported in the Snoqualmie Pass area Monday were loose wet avalanches that failed as the sun heated the recent snow.

In other zones, human triggered avalanches were reported Sunday and Monday. Many of these avalanches failed on a layer of buried surface hoar from December 26. Currently, we do not have any reports of this layer in the Snoqualmie Pass area. That doesn’t mean it isn’t there. You would be most likely to find a layer of buried surface hoar further east in the zone or at higher elevations, where the rain did not destroy it. If you find evidence of this layer, please let us know by submitting an observation.

If you use the nice weather to travel to higher elevations or into more remote areas take time to stop and observe the snow. Due to stormy weather we have not received any information from higher elevations in quite some time.  

Weather Synopsis

Weather Synopsis for Tuesday night through Thursday

High clouds are moving into the forecast area on New Year's Day as an upper ridge flattens along the coast. The ridge will weaken further overnight allowing increasing frontal moisture to arrive in the form of thickening clouds.  A shift to light westerly flow Tuesday has allowed warming temperatures under the ridge.

A cloudy day is in store for Wednesday as an offshore frontal system nears the coast. Some very light precipitation may reach the Olympics and Mt Baker area by late Wednesday afternoon.

Frontal precipitation will increase overnight Wednesday, mainly light in all areas except the Mt Baker area where significantly heavier precipitation is expected at rising freezing levels. 

Moderate to heavy precipitation will spread over the area Thursday with a sharp delineation in intensities from north to south. Mt Baker area will receive heavy precipitation with only very light precipitation making its way to the Mt Hood area.  Freezing levels should be at maximum levels Thursday morning before beginning to lower Thursday afternoon in the wake of a frontal passage. 

It currently does not look like the easterly winds through the passes will be strong enough to save the passes from another rain event Thursday.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.