Avalanche Forecast
Issued: Feb 28th, 2020 4:00PM
The alpine rating is Wind Slabs and Cornices.
, the treeline rating is , and the below treeline rating is Known problems includeWe're looking at a warm Friday night which may keep wind slabs human triggerable Saturday. The freezing level got to at least 2300 m Friday which is going to make for some funky riding conditions. Cornices and riding quality are probably the biggest concerns Saturday.
Summary
Confidence
Low - Uncertainty is due to rapidly fluctuating freezing levels.
Weather Forecast
Warmer funky weather is with us for the forecast period.
FRIDAY NIGHT: Freezing level around 2200 m in the early evening lowering to about 1400 m by dawn, moderate to strong southwest wind, 3 to 5 mm of rain expected at lower elevations, wet heavy snow near ridge top,
SATURDAY: Broken cloud cover, freezing level lowering from 1800 m to 1500 m, light to moderate southwest wind, 3 to 6 cm of snow expected up high, rain down low.
SUNDAY: Broken cloud cover at dawn clearing to just a few clouds in the late afternoon, freezing level beginning at valley bottom rising to 1500 m during the day, light variable wind, no precipitation expected.
MONDAY: Broken cloud cover, freezing level beginning at valley bottom rising to 1500 m during the day and then staying there until Tuesday night, strong southwest wind, no precipitation expected.
Avalanche Summary
It's warm Friday afternoon, and Saturday looks like it will be warm too. Once temperatures cool off the old wind slabs will likely be done. In the meantime the warm temperatures may allow for continued reactivity of the wind slab near ridge crest.
There was a report of a size 2 skier triggered slab on Thursday on northeast aspect near ridge top in the Lizard Range. There were also reports of falling chunks of cornice, but they did not initiate slab avalanches when they impacted the underlying slopes.
No new avalanches were reported on Wednesday.
A few size 1.5 skier triggered avalanches were reported on Tuesday that appeared to fail on persistent weak layers roughly 30-40 cm below the surface. One was triggered by a skier on a east-facing slope at 1900 m and ran on the early February crust/facet combo. This MIN observation from Harvey Pass shows a skier triggered avalanche on an north-facing slope that looks like it could have run on surface hoar.Â
Snowpack Summary
Friday was quite warm which allowed for further settlement of the upper snowpack. 20 cm of settled snow rests on a variety of old surfaces including a firm crust on solar aspects, soft faceted snow, possibly a spotty surface hoar layer and old wind slabs near ridge crest. Recent snow has been blown into variable wind slabs in exposed terrain features, especially those near ridge crest.
A thick rain crust that has facets associated with it sits 30-60 cm below the surface and can be found up to ridge top. The avalanche listed above is the first activity that we've seen on the crust since February 17. Â
The mid-pack is well settled and strong, but the base of the snowpack contains basal facets that are most prominent in shallow rocky start zones.
Terrain and Travel
- Caution around slopes that are exposed to cornices overhead.
- Small avalanches can have serious consequences in extreme terrain. Carefully evaluate your line for wind slab hazard before you commit to it.
Problems
Wind Slabs
We're looking at a warm night Friday, so there may still be a chance of wind slabs in extreme terrain, but once temperatures cool wind slabs probably won't be much of a problem.
Aspects: All aspects.
Elevations: Alpine.
Likelihood
Expected Size
Cornices
Continued warm temperatures may allow for natural cornice failure Saturday.
Aspects: North, North East, East, South East, South.
Elevations: Alpine.
Likelihood
Expected Size
Valid until: Feb 29th, 2020 5:00PM