North Columbia

A rapidly rising freezing level, rain, and strong warm wind are expected to initiate large natural avalanches that could run into areas we normally think of as "safe" in the valley bottom. Travel in or below avalanche terrain is not recommended.

Moderate - Timing or intensity of solar radiation is uncertain on Tuesday

Tuesday delivers a significant warm up to the Columbia Mountains, precipitation is expected to fall as rain as high as 2000 m, possibly even 2500 m. Wednesday is ever so slightly cooler and then we should return to a more seasonal temperature regime on Thursday. TUESDAY: Scattered cloud cover, freezing level beginning around 1200 m, may rise as high as 2500 m, moderate to strong southwest wind, 3 to 6 mm of precipitation possible.WEDNESDAY: Scattered cloud cover, freezing level beginning around 1500 m rising to about 2000 m, light west/southwest wind, trace of precipitation possible.THURSDAY: Broken cloud cover, freezing level beginning around 500 m rising to about 1500 m, light variable wind, 2 to 6 mm of precipitation possible.

On Sunday natural loose wet avalanches to size 2 were reported from all aspects (including north) as high as 2800 m. This activity is expected to intensify Tuesday.No new avalanche activity to report from Saturday.On Friday a size 1.5 persistent slab avalanche with a 60 cm crown was skier triggered on a north facing slope at 2000 m. Natural loose dry and loose wet avalanches were observed on north and west facing slopes above 2000 m.On Thursday warming temperatures initiated large loose wet avalanches to size 3 on south facing aspects between 2100 and 2700 m in the neighboring Glacier National Park. A small shallow wind slab was accidently triggered by a skier on a steep/unsupported east/southeast facing feature at 2200 m too.

5 to 10 cm of new snow fell Saturday with moderate southerly wind. This snow rests on a crust that is present on all aspects below 2000 m, and extends up to about 2500 m on south facing aspects. The storm snow be be sitting on surface hoar on polar aspects (north and east) at upper elevations. The main concern is the mid-March Persistent Weak Layer (PWL) which is now 60 to 110 cm below the surface. This layer is composed of a crust on all aspects at low elevations. At upper elevations the layer presents as a crust on solar aspects (those that face south and west) and buried surface hoar on polar aspects. The reactivity of this interface has been steadily decreasing and while the likelihood of triggering a deeper persistent slab avalanche is lowering, the consequence of doing so remains high. Solar aspects are expected to be the most suspect as the freezing level begins to rise Tuesday and Wednesday.Deeper persistent weak layers from January and December are still being reported by professional observers, but are generally considered dormant.