Expect new snow and strong winds to form storm slabs and grow cornices. Sloughing, and cracking around skis and sleds are signs that the new snow is bonding poorly to the old surface. Avoid wind loaded areas with pillowy or chalky looking snow.
Confidence
Moderate - Forecast snowfall amounts are uncertain
Weather Forecast
TONIGHT: Flurries. Accumulation 5-15 cm. Ridge wind strong to extreme, southwest. Temperature -12. Freezing level valley bottom.SUNDAY: Mostly cloudy, light flurries. Accumulation 2-5 cm. Ridge wind strong, west. Temperature -10. Freezing level valley bottom. MONDAY: Cloudy, flurries. Accumulation trace. Ridge wind moderate, southwest. Temperature -6. Freezing level 600 m. TUESDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind light to moderate, southwest. Temperature -5. Freezing level 900 m.
Avalanche Summary
There have been no new reports of avalanches since Wednesday (Feb 21) when a size 2, natural cornice release was reported on a southeast aspect at 1900 m in the northern part of the region.Prior to that on Tuesday, there was a report of a skier triggered size 1.5 soft, wind slab release (25-50 cm deep) on a northeast-facing open, treeline slope at 1900 m, that failed on the mid-February surface hoar layer.Although deeper, persistent avalanche activity has become less frequent over the past week, light triggers in shallow rocky areas, as well as large triggers such as a cornice collapse or step down from a wind slab release, still have the potential to result in large destructive avalanches.
Snowpack Summary
About 5 to 15 cm of new snow now covers the old snow interface which consists of sugary facets as well as sun crust on solar aspects and surface hoar on shaded, wind-sheltered slopes.Below the old interface lies another interface, with similar character and distribution that was buried mid-February and is now 25-50 cm below the snow surface. This layer has been reactive in recent snowpack tests and recent avalanches have been reported to have failed on this layer in the past week.Within the mid and lower snowpack are several persistent weak layers that are slowly beginning to show signs of improving but still remain suspect. Two surface hoar/ crust layers buried in January are now 100-150 cm below the snow surface. At least one of these layers can be found on all aspects and elevations.Deeper in the snowpack (150 - 200 cm deep) is a facet/crust/surface hoar layer buried in December that is most prevalent at treeline elevations and below.Near the base of the snowpack is a crust/facet combo layer buried in late November.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.