Avalanche Forecast

Elevated snow levels and light to moderate rain, except heavy at Mt. Baker, should continue for areas away from the Cascade Passes. The Passes may continue to flirt with light snow, rain or mixed precipitation Thursday night. 

Steadier precipitation should transition to light to moderate showers with snow levels falling to 4500 feet by Friday afternoon. Light amounts of new snow should bond well to the wet and refreezing surface on Friday. 

Persistent weak layers received a good test over the last 48 hours. We will continue to list persistent slab as a problem until more information becomes available, but it's likely that PWLs have been eliminated from the volcanoes due to warmer and wetter conditions, but may still linger in the Cascade Passes although more difficult for a human to trigger. 

Loose wet avalanches should be the main avalanche problem Friday with plenty of wet snow in the upper snowpack. Natural wet loose avalanches are possible but human triggered wet loose avalanches should be likely on steeper slopes. Be especially wary near terrain traps, where even a small avalanche could have unintended consequences.

Storm slab avalanches are possible in the Cascade Passes and higher elevations that only saw a brief period of rain. It's difficult to predict the likelihood of storm slabs in the Passes given the potential for different precipitation types and crust layers. New wind slab may begin to build on lee easterly slopes above treeline Friday but should be fairly shallow. 

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 January 3rd and 11th. One or both of these layers have been seen in snow pits by NWAC pro observers and avalanche professionals the past few days ranging from Mt Baker to the Crystal Mountain area. These persistent weak layers are most likely to be found on non-solar (northerly) aspects in the below and near-treeline band. However, we cannot rule out the above treeline elevation bands so the problem is listed for all three bands. We will have to see how the PWLs survived the most recent storm cycle. 

A progressive pattern brought a series of storms to the Northwest with several feet of new accumulating along the west slopes. The most recent frontal system brought up to a foot of snow late Wednesday night through early Thursday morning. 

Warmer air brought a quick change to rain for areas away from the Passes like Mt. Baker, Paradise and Crystal. 2 to 4 inches of water has fallen over the west slopes in the last 48 hours through 5 pm Thursday, with the heaviest rainfall in the Mt. Baker area. The Passes were slower to warm on Thursday. Freezing rain was reported up to 5000 feet by Alpental pro-patrol by 9 am Thursday morning. 

Snow and Avalanche Observations

NWAC Pro observer Dallas Glass found the buried surface hoar layer well intact 45-50 cm down on a west aspect of Kendall Peak Saturday. Backcountry rangers at Paradise reported buried surface hoar in snow pits at 5900 feet last weekend. Earlier in the week, Alpental pro-patrol identified the two buried weak layers down 70 and 100 cm between 3000-4000' but have not seen any recent avalanches release to these layers. 

NWAC pro observer Ian Nicholson at Yodelin on Monday found both the 1/3 and 1/11 surface hoar layers buried about 40 and 75 cm respectively on north aspects, within the below treeline elevation band. Tests indicated propagation was likely, with the deeper layer slightly more reactive.

NWAC observer Lee Lazzara was in the Canyon Creek area of Mt. Baker and found buried surface hoar 55 cm down (~2 ft) around the 5500 ft level and likely to propagate in column tests. Lee also observed a snowmobile triggered slide from a distance that broke 500' feet across the slope near treeline. This large slab avalanche likely released on the buried surface hoar layer. Luckily no one was caught. 

Observations were limited on Thursday due to the storm and poor visibility, but Stevens Pass pro-patrol reported widespread and sensitive 14-16" storm slabs easily triggered by ski cutting or explosives Thursday AM. Alpental pro-patrol reported similar sensitivity with 8-10" storm slabs Thursday morning. Below 4000' at Alpental, the snow became moist and loose wet avalanches entrained surface snow. At Heather Meadows (Mt. Baker), steady rain had percolated several feet down into the snowpack at 4200' by mid-day Thursday.