Avalanche Forecast

A weak vertically aligned low pressure system should drop south over the northeast Pacific Ocean and Northwest coastal waters Sunday night and Monday. This should cause decreasing winds with mostly sunny weather over the north Cascades and partly sunny weather in the south Cascades on Monday.

The mix of winter and spring snow conditions should continue on Monday. The main concern should begin to shift to wet loose avalanches on Monday. This should be likely on solar slopes in all 3 elevations bands on Monday and will be possible on non-solar slopes. Watch for wet surface snow deeper than a few inches, roller balls in surface snow and small natural wet loose releases that usually precede more major wet loose snow avalanches. Avoid terrain traps where a small but powerful wet loose avalanche could have unintended consequences.

Watch for areas of recent wind slab on lee slopes. This is likely on shaded north to east slopes near and above treeline. Watch for signs of cracking or firmer wind transported snow and approach open lee slopes with caution.

East winds will be seen in the lower Cascade passes mainly Stevens and Snoqualmie on Monday. But warm afternoon temperatures and solar effects should consolidate or melt surface snow in the lower Cascade passes on Sunday and Monday and limit or mostly eliminate snow available for transport. So new small areas of wind slab will not be listed as a concern at Stevens and Snoqualmie on Monday. But remember to also make you own evaluations for this concern if you are in these areas on Monday.

Recent storm slab may need another day to stabilize on Monday. This is possible on sheltered slopes where there was recent heavy snowfall or graupel which may have formed temporary weaker storm layers. This shorter lived concern should be above treeline due to cooler temperatures there.

Remember to watch for cornices if you venture onto ridges on Monday and avoid slopes below cornices. Cornice failures are normally seen during the transition to spring weather.

The weather pattern got active again over the Northwest starting last Tuesday. There has been about 1-3.5 feet of snowfall in the 5 days ending today at higher elevation NWAC stations near and west of the crest. Less snow has been seen at lower elevations.

Avalanche conditions also got active this week. We are now seeing winter snow conditions mainly on shaded slopes at higher elevations and spring snow conditions on solar slopes and at lower elevations. Here are a some reports for the past few days.

NWAC observer Jeff Hambelton was near Church Mt along the Mt Baker highway on Wednesday. He saw several small but natural and human triggered storm slab avalanches on lee aspects near treeline likely failing within the new storm snow. He was at Table Mt near the Mt Baker ski area on Thursday and saw widespread natural wet loose avalanches on all aspects with solar effects and daytime warming.

Storm slab on Church Mtn 26 March by NWAC observer Jeff Hambelton.

A front crossed the Northwest on Friday. The Mt Baker ski patrol reported large ski triggered wet loose avalanches on Friday. The Alpental ski patrol and Snoqualmie DOT reported a natural cycle of loose snow avalanches on late Friday which were drier in the upper elevations and wetter at the lower elevations. NWAC observer Tom Curtis was at White Pass on Friday and reported 4-8 inch wind slab conditions at about 5800 feet.

Wind slab conditions near White Pass on 28 March by NWAC observer Tom Curtis.

Reports from over the weekend include the following. Ski cuts Saturday at the Mt Baker ski area gave mainly isolated wet loose avalanches below 4000 feet. NWAC observer Jeff Hambelton on the west side of Mt Baker Saturday reported building wind slab above about 6000 feet. The Alpental ski patrol reported a natural cycle of loose snow avalanches on Saturday night. Today the Mt Baker and Alpental ski patrols reported isolated 4-8 inch storm slab avalanches releasing in storm layers.