Avalanche Forecast

A short break in the weather Tuesday will allow avalanche hazard to slowly decrease. Be patient and allow these new wind and storm slabs to gain strength.

Use visual clues such as snow drifts, fresh cornices, and firm snow surfaces that crack to identify and avoid steep wind loaded slopes. Wind slabs may exist near ridgeline and on cross-loaded mid-slope features at higher elevations. Give these newly formed wind slabs time to heal.

Significant snowfall totals were reported across the area Monday. While storm slabs are gaining strength, you my still trigger a storm slab in terrain greater than 40 degrees, near convex rollovers, or on unsupported slopes. Stay off of these slopes Tuesday while the new snow continues to bond and strengthen. Periods of prolonged sun may change how these storm slabs react. If you experience any cracking, collapsing, or see new slab avalanches avoid nearby avalanche startzones.

Expect new rollerballs, pinwheels, and small loose wet avalanches to occur during periods of sunshine. The April sun is very strong and snow conditions can change quickly. Be cautious on steep slopes where the consequences of even a small loose wet avalanche can be high.

In general 12-15 inches (30-40cm) of new snow fell Sunday in Monday with locally higher amounts near Snoqualmie Pass. This new snow fell on a firm melt-freeze crust in many locations. Several observations from around the area reported generally loose surface snow conditions with a moderate bond to the old crust. Near and above treeline, moderate to strong winds drifted snow forming new wind slabs on lee slopes. Snow drifts of 15-22 inches (40-55cm) were reported. Neither natural nor human triggered slab avalanches were reported from backcountry areas Monday.

Below the recent snow a variable upper snowpack can be found. Generally layers of firm melt-freeze crusts and strong rounded grains have been reported.

Two notable exceptions to monitor are:

Mount Baker Area: Observers have reported at least five triggered avalanches Friday and Saturday in the Mount Baker area on N-E aspects at upper elevations. Profiles near the crown of some of these avalanches found buried surface hoar.  We are currently dealing with avalanche problems related to the recent storms and blowing snow, but you may experience these avalanches breaking in surprisingly reactive ways. You can use snow profiles and snowpack tests to monitor these avalanche problems and the potential for them to persist into the future. Buried surface hoar should show up as a weak thin grey stripe 2-3 feet (60-90cm) below the snow surface on shaded, northerly slopes above 5,000ft. Time will be the judge whether this weak layer remains a problem for triggering avalanches after the storm instabilities stabilize.

Crystal Area: Several avalanches 3/24-3/27  failed on a layer of weak older snow buried on 3/22. Observations still report test results on this layer, but it has become difficult to trigger related avalanches. In some locations you may find a layer of small sugary facets above a firm melt-freeze crust. On shaded northerly slopes this layer may show up as buried surface hoar. This layer has generally been reported 24-36” (60-90cm) below the snow surface and may be most prevalent above 5,500ft.

Below the top 2-3 feet (60-90cm), the snowpack is generally well bonded and lacking interfaces of concern. The much older 2/8 melt-freeze layer can still be found over 6 feet (200cm) deep in the snowpack. While this layer isn't listed in our current avalanche problem set, it may reawaken if it becomes wet.

North

On Monday Mt Baker Ski Patrol reported 12 inches (30cm) of new snow moderately well bonded to the old snow surface. Loose snow conditions were observed.

On Friday, NWAC Observers Lee Lazzara and Simon Trautman traveled in the Bagley Lakes area. They reported 3 triggered or natural avalanches about 1 foot deep on north aspects near treeline on slopes with recently drifted snow. The observers found a thin weak layer of surface hoar buried 3/25 at the interface of concern.

Central

NWAC avalanche forecaster Josh Hirshberg was at Stevens Pass Monday. Josh reported 16 inches (40cm) of new snow in sheltered locations. Near ridgeline, winds were actively transporting snow, forming drifts up to 22 inches (55cm) deep. No new avalanches were observered.

An avalanche professional in the Snoqualmie Pass area found generally good bonding of the new and old snow with loose snow surface conditions. No new avalanches were observed.

Alpental Ski Patrol reported loose avalanche conditions Monday.  No new natural avalanches were seen.

South

NWAC professional observer Jeremy Allyn traveled in the Crystal backcountry Monday. Jeremy found wind transported snow above 6000 feet. The new snow was moderately bonded to the old snow surface with the bond strengthening during the day. As the sun came out, sunny aspect quickly became moist to wet and produced rollerballs.