Avalanche Forecast

The next very strong cold front will begin to reach the Olympics Sunday midday. This will begin to cause stormy weather with strong winds and heavy snowfall. This system should have cooler temperatures and lower snow levels than the past few systems. Rapid loading should begin to cause new storm slab to begin to build on most sheltered aspects in all the elevations zones Sunday afternoon. Wind transport should cause new wind slab to begin to build on lee slopes mainly near and above treeline. This will begin to add further loads to the rain crust from Wednesday or deep layers. Natural or triggered large avalanches should become possible Sunday midday.

The storm should peak in the Olympics Sunday afternoon and evening. Rapid loading and wind transport will cause storm and wind slab to further build and become deep Sunday afternoon and evening. An avalanche cycle is likely in the near and above treeline zones. Natural or triggered large avalanches are likely near and above treeline Sunday afternoon and evening.

Recent Regional Weather and Snowpack

An extended dry mild period was seen the latter half of January. The was followed by very cold weather and periods of low density snowfall in early February. Now for the past 5 days the Northwest is getting pummeled by daily frontal systems producing periods of strong winds, periods of warmer higher density snowfall and rain during periods of generally warmer temperatures.

Water equivalents/snow for the past 5 days mostly range as follows: Olympics and Cascades near and west of the crest 3-7 inches WE/2-4 feet of snow, east of the crest 1-4 inches WE/1-2 feet of snow, and at Mt Hood 10-12 inches WE/2-3 feet of snow! Note this is generally heavy wet snow for all areas especially at Mt Hood!

Regionally this weather is generally building heavy denser snow layers over colder lower density and faceted snow from early February over potential hoar frost, faceted snow and crusts from late January. So it is no surprise there has generally been a lot of regional avalanche activity especially in the Washington Cascades and at Mt Hood the past couple days. Several widespread natural avalanche cycles have run their course over the past several days with the largest cycle occurring late Tuesday to early Wednesday.

Similar weather and snowpack structures around the west have lead to numerous recent fatal avalanche accidents including in northeast Oregon on Tuesday.

Hurricane Ridge

Our NWAC observer Tyler Reid at Hurricane Ridge on Friday reported a ski triggered D2 avalanche on a northeast slope at 5200 feet. He is also reported 20 cm of F storm snow over a rain crust from Wednesday over another 20 cm of F snow. The crust layer at 20 cm will probably be the interface to watch during the upcoming storm on Sunday.

Photo by NWAC observer Tyler Reid showing F over crust over F snow on 14 February.

Snow pit tests by Tyler on Saturday gave moderate to hard, sudden planar results and unlikely propagation.

Limited snow at the lowest elevations will limit the avalanche danger there. The mid and base pack should still consist of mostly stable crusts and melt form layers from periods of warm weather earlier this winter.