Avalanche Forecast

A cooling trend continues with scattered light showers overnight Tuesday and early Wednesday with light to moderate winds. Greater new snow is possible from Stevens to Snoqualmie passes due to convergence.

Updated Wednesday morning, storm slab has been added to the forecast from Snoqualmie Pass northward where new snow fell at heavier rates late on Tuesday into Wednesday, in some cases into the below treeline areas. The snow came in on a cooling trend, but temperatures are warm enough in some areas that storm slab may still have formed.

The 5-15" of recent snow since Sunday will be available for wind transport and will support wind slabs forming near and above treeline on a variety of exposed slopes.

The next strong storm is forecast to arrive Wednesday night, however if the storm arrives earlier than forecast expect increasing danger late Wednesday. Watch for changing weather conditions through the day Wednesday and be prepared to alter plans accordingly.  

Below treeline expect strengthening and refreezing of Tuesday's moist to wet surface snow. Only shallow new snow is expected above a very strong overall snowpack in most below treeline areas.

Early season hazards still exist. Many creek beds have still not filled in for the winter and crusts in many areas are quite firm.

From Sunday through Tuesday, most NWAC stations above 4000' received 5-10 inches of new snow with generally less accumulation below. A mixture of rain and snow maintained shallow new snow or wet surface snow conditions. Continued cooling is strengthening the wet snow by late Tuesday.

The upper snow layers below snowfall received since Sunday, is a mix of strong layers including multiple rain or freezing rain crusts of varying supportability.  

Reports continue to indicate a strong upper snowpack with no notable layers of concern and a multitude of crusts formed over the last two weeks. 

Observations

North

On Tuesday, the Mt Baker pro patrol reported sensitive 5-6" soft slabs releasing above the most recent rain crust (1/5), both with ski and explosive triggers.

NWAC pro-observer Lee Lazzara was in the Bagley Lakes area on Sunday.  Lee found gusty winds transporting new and recent snow onto various aspects and forming thin but sensitive wind slab through the early afternoon well down into the below treeline band. The 1/5 rain crust was ski supportable. Visibility was poor but glide cracks had re-opened on some steep rock faces due to the heavy rain event that ended Friday.  No new avalanche activity was observed.

A NWAC public observation from Sunday did show that these small, sensitive wind slabs were reactive to human triggering on Sunday.

Central

NWAC professionals on Snoqualmie Mountain Tuesday reported a major distinction in snowpack with elevation. Below treeline, a mixture of rain or wet snow maintained shallow wet snow conditions making loose-wet avalanches possible on steep slopes involving about 4-6 in. of snow above the 1/5 crust layer. Near and above treeline, especially above 5200 ft, a lack of crust, recent dry snow and light to moderate winds were actively forming shallow new wind slabs in exposed terrain.

Pro Patrol at Stevens Pass reported observing debris from a widespread loose-wet cycle on all aspects near treeline that likely occurred Sunday night. The slides were small and were no longer entraining much snow during ski cuts by Monday morning.

NWAC professionals traveled in both the Snow Lake and Kendall Peak areas of Snoqualmie Pass on Sunday. Thin wind slabs, up to 8" (20 cm), were building on a north aspect above Snow Lake at 4600 ft and reactive in column tests, failing on the 1/5 crust as of mid-day.  In the Kendall area, 1-4" of snow was reported above the 1/5 crust. Little active snow transport was observed to ridgecrest.  A thin rain or freezing rain surface crust was forming later in the day.  No new avalanche activity was observed.   

NWAC pro-observer Jeremy Allyn was in the Smithbrook/Rainy Pass area east of Stevens Pass on Sunday. About 3-4" of recent and new snow was well bonded to the 1/5 crust which was semi-ski supportable. Travel conditions were difficult. No new avalanche activity was observed. 

South

A professional in the Paradise area Sunday reported a switch from snow to freezing rain/ice pellets by late morning. This trend likely continued into Sunday afternoon as light to moderate precipitation produced no new snow at the Paradise weather station. As of mid-day Sunday, 4-6 inches of recent and new snow was well bonded to the 1/5 crust with a thin freezing rain crust noted at the surface. Some wind transport was occurring near treeline above 6000 feet due to moderate west winds. No new avalanche activity was observed.