Avalanche Forecast

Another fast moving and powerful storm system will impact the Pacific Northwest on Tuesday.  Snowfall will increase first in the Olympics Tuesday morning and spread into the Cascades by late morning.  A more southerly flow out ahead of frontal boundary should bring rapid loading rates first to the more northerly aspects and then during and following the frontal passage to more easterly aspects as winds veer to the west by Tuesday afternoon. A warmup preceding the frontal passage should cause rain at lower elevations and denser wind and storm slab elsewhere. Snow levels should fall again by late Tuesday afternoon. 

New storm slab will form on all sheltered aspects. New potentially deep wind slab will develop on lee N thru SE slopes. Natural or triggered avalanches will be likely at all elevations. Direct action avalanches that release initially in storm layers seem likely to step down to deeper layers. Wet loose avalanches should become more likely in the late morning and early afternoon at elevations up to 4500 feet and may entrain large amounts of the most recent storm snow. 

Travel in avalanche terrain is not recommended on Tuesday.

Recent Northwest Weather

An extended mild and mostly dry period occurred over the latter half of January which allowed a variety of crusts to form. Very cold weather followed in early February which produced low density snowfall and strong temperature gradients in the upper snowpack that allowed near surface faceting and broke down previously strong crusts buried in late January. During the last week the Pacific Northwest has been pummeled almost daily by frontal systems producing periods of strong winds and intense snowfall accumulation at fluctuating and generally moderate snow levels.

Water equivalents in the Olympics at the NWAC weather station and the NRCS Snotel at Waterhole over the last week are 5-6 inches with snowfall around 4 ft range. Expect wind loaded slopes to hold much more new snow from the past week than the generally sheltered weather stations.  About 18-24" of new snow has fallen in last 36 hours ending 4 pm Monday.  

Observations near Hurricane Ridge

At Hurricane Ridge this weather has been building deep new snow over a rain crust from Wednesday, which lies over colder lower density snow from earlier in February.  In sheltered non-solar aspects, surface hoar may be buried above the late January crust.

A park ranger and NWAC observer Tyler Reid at Hurricane Ridge Friday reported one ski triggered D2 avalanche on a northeast slope at 5200 feet on Friday.

Snow pit tests by Tyler on Saturday on a SE aspect @ 5200 ft gave moderate to hard, sudden planar results with potential to propagate across the failure plane on the melt freeze crust 20 cm down (this layer is now further down).  You can view a great video by Tyler explaining his test results. 

A natural avalanche, estimated at size D2 was visible below the Hurricane Ridge road at about 5100 ft on a NE aspect on Monday.

Limited snow at the lowest elevations will limit the avalanche danger but be wary that avalanche paths on solar aspects and lower elevations are finally beginning to fill in. The mid and base pack should still consist of mostly stable crusts and melt form layers from periods of warm weather earlier this winter.