Avalanche Forecast

A slow warming trend will begin late Wednesday night and continue on Thursday as a frontal system stalls offshore. Moderate snow and strong alpine winds should target the northeast Cascades Thursday. Strong alpine winds but much lighter precipitation amounts are forecast for the central and southeast Washington Cascades Thursday. A period of freezing rain is possible for the lower east slopes and valleys Thursday morning through mid-day with a delayed warm-up versus the west slopes. 

In the northeast Cascades, moderate snowfall should gradually stress and load buried weak layers, potentially resulting in large and destructive avalanches. Travel in backcountry terrain is not recommended Thursday, especially near and above treeline where wind loaded slopes should tip the balance for natural avalanches from possible to likely.  The danger from storm and wind slab avalanches will increase on Thursday as well, with warming throughout the day building an upside down snowpack and winds transporting snow to lee NW through SE aspects.  

The avalanche forecast will be trickier for the south and central-east Cascades where precipitation should be lighter. However, shallow new or lingering storm or wind slabs or small loose wet avalanches could step down to areas where persistent weak layers are reactive resulting in large avalanches in specific areas. 

Loose wet avalanches for the south and central east Cascades are likely to be small and confined to steeper slopes.  Be especially wary near terrain traps, where even a small avalanche could have unintended consequences.

Weather

Two fair weather periods earlier this month allowed surface hoar and near surface faceting to occur. These persistent weak layers were buried intact on Jan 3rd and 11th and have been reported through Monday from the Methow, the Icicle Creek area, the Blewett Pass area, the Nason Ridge area and the Chiwaukum range east of Stevens Pass. It's safe to say this layer is extensive throughout the east slopes.

A parade of weather systems this week added about .5-1 feet of snowfall to the east slopes from about Friday to Sunday.

Only a few inches of additional snowfall accumulated with a weather system that passed through Oregon Tuesday and Tuesday night. 

Snow and Avalanche Observations

NWAC pro observer Jeff Ward on Sunday found the persistent weak layer on shaded slopes up to about 5000 feet in the Early Winters drainage. This layer was reactive prompting very cautious terrain selection of lower angled slopes. A video by Jeff shows a similar persistent weak layer and a remotely triggered avalanche in the Icicle Creek Drainage near Leavenworth on Monday.

On Sunday the observer at the Scottish Lake High Camp in the Chiwaukums reported a natural 12 inch slab release on a southerly aspect around 5000 feet and easily identified two buried surface hoar layers in snowpits on a north-northwest slope at 5500 feet.

On Monday NWAC pro observer Tom Curtis was on Diamond Head near Blewett Pass in the 4-6000 foot range and found a persistent weak layer at 30-35 cm on north to east aspects with propagation indicated via PST and ECT tests. A 50 foot crack also released upon approach to a north facing starting zone indicating this layer remains reactive. Tom's video is here.

A report via the NWAC Observations page from Wedge Mountain for Monday reports a skier was caught and carried but not injured by a 18-24 inch storm slab avalanche.

NWAC pro observer Tom Curtis visited the Rainy Creek drainage of the central east zone today and traveled from 2-5800 feet and found limited lingering wind and storm slab. He did not find any signs of lingering persistent weak layers.

NCMG on Monday found several persistent weak layers near Goat Peak at 6400' on a north aspect, reactive to column test and sensitive to human triggering.  

Remotely triggered avalanches on persistent weak layers were reported in TAY in the Mission Ridge area Monday.