The Public Avalanche Forecasts and Danger Ratings will come to an end on Tuesday. General spring messaging will be found under the Forecast Details tab below.
Confidence
Fair - Due to limited field observations
Weather Forecast
The Interior will remain under a cool, dry North-West flow through Tuesday. A slow warming trend will persist through the end of next week.Sunday: Scattered-broken cloud cover, allowing some sunshine through. Ridgetop winds will blow light from the North. Freezing levels 1400 m and falling to valley bottom overnight.Monday/Tuesday: Mostly clear, sunny skies. Ridgetop winds will blow light from the NW. Freezing levels 1700 m in the afternoon and falling to 1000 m overnight.
Avalanche Summary
On Friday, reports of the new storm snow was sluffing from steep terrain up to size 2.
Snowpack Summary
At higher elevations up to 25 cm of new snow sits on a series of melt-freeze crusts (solar aspects) and some smaller surface hoar crystals (northerly aspects). Touchy wind slabs exist on lee slopes and behind terrain features and cornices are huge, threatening slopes below.Deeper in the snowpack (60-120 cm down) a weaker interface exists comprising of crusts, and surface hoar. Earlier this week, very large avalanches were reactive on this interface in the neighboring Glacier National Park. I would practice caution and remain suspicious of steeper, high alpine slopes.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.