Avalanche Forecast

An approaching storm will bring increasing clouds and strengthening winds through the morning Wednesday. Snowfall will arrive midday Wednesday and increase through the afternoon with warming. 

The warming and beginning of the new snow loading Wednesday afternoon, will begin to stress the significant recent storm snow.  The avalanche danger will gradually increase through the afternoon Wednesday, however the significant loading and heavier precipitation rates are likely to hold off until Wednesday night and into Thursday.

If the approaching storm arrives sooner than forecast or with, initially heavy precipitation, the avalanche danger could increase more rapidly than expected. Watch for changing conditions and be prepared to alter plans accordingly.

Note that deep snow conditions now exist in most terrain. Travel with a partner and use good communication and keep your partner in view at all times. 

Weather and Snowpack

A strong storm cycle began Friday with 3-4 feet of snow recorded along the west slopes on average, through Monday afternoon. A slow warming trend affected all areas Saturday with rain reaching 4000-4500 feet in the south Cascades. Cool easterly flow kept temperatures locally cool at Pass level at Stevens and Snoqualmie Pass through the day Saturday, with a warm-up Saturday midday following a switch to westerly flow. This created a weak crust layer that has now been found both at Stevens and Snoqualmie passes, down about 3 feet. 

Sensitive but generally shallow storm slabs were reported throughout the west slopes on Saturday from ski area control work and several backcountry observations. Intense precipitation rates Sunday morning became light to moderate during the day. Continued moderate to occasionally heavy snow showers fell through the day Monday at cool temperatures. The cooling trend Monday and settlement rates during the previous warming should all help the storm snow to become less sensitive to trigger.

A nice day Tuesday with light wind and sun or filtered sun and high clouds allowed for further snowpack settlement and stabilization of the deep recent storm snow.  Most NWAC snowdepth gages settled about 6 inches or more during the day Tuesday.

Recent Observations

North

On Tuesday, Mt. Baker pro-patrol reported ski triggered soft slab avalanches of 8-10 inches on average, though they were not propagating widely as the older deep storm snow was showing signs of settlement and stabilization. There was evidence of a widespread natural cycle, likely Monday night on Table Mountain, with many crowns estimated in the 2-4 ft range.

NWAC's Lee Lazzara was up the Glacier Creek area off Hwy 542 Tuesday, reporting numerous triggered storm snow soft slabs, on average 40 cm (16") on steep test slopes on both southerly and northerly facing slopes. Another triggered slide was evident from a nearby party that may have been a bit deeper, about 2 feet. 

Central

Reports from both Snoqualmie and Stevens passes Tuesday indicated continued storm snow settlement and stabilization, in the near and below treeline terrain. A thin melt freeze crust formed midday Saturday, 2/4 produced positive snowpit results but no avalanches were produced. The storm snow is gaining strength, showing increasing resistance with depth and providing some excellent conditions.

South

NWAC pro-observer Dallas Glass was in the Crystal backcountry in Bullion Basin Sunday and found a reactive storm layer 35-40 cm down in snowpit tests on all aspects below and near treeline. Shallower storm slabs could be triggered on test slopes. Storm snow from this cycle had settled to about 60-65 cm. No natural avalanches were observed and recent wind transport was localized to near the ridgeline.