Issued: Mar 18th, 2023 4:00PM
The alpine rating is Loose Wet, Wind Slabs and Persistent Slabs., the treeline rating is , and the below treeline rating is Known problems include
The March sun packs a punch and can quickly destabilize the snowpack. Be suspect of sunny slopes or overhead hazards like cornices during the heat of the day.
On Friday, loose wet avalanches to size 2.5 were observed in solar terrain.
On Tuesday, a natural size 2 wind slab and size 3 glide slab were reported both around 1300 -1500 m. A skier-triggered storm slab was also reported on Zoa. The slab was a size 1.5 and was triggered near the top of the slope with no involvement. It was 40 cm deep and slid clean on the underlying old snow surface. Check out the MIN HERE. Thanks for the report and happy to hear everyone was ok.
A natural persistent slab size 3 was reported on Tuesday but it's suspected that it failed Monday during the storm. This avalanche happened on a shady aspect at 1800 m, with the failure plane unknown but suspect an early March interface.
Daytime warming and solar radiation will promote moist snow surfaces, destabilizing the upper snowpack on all aspects upwards of 1800 m and higher on solar slopes. Cornices loom over ridgelines and may become weak during periods of solar radiation and warming.
The recent 40 cm of storm snow covered a variety of old snow surfaces, including a sun crust on solar aspects, a melt-freeze crust at lower elevations and a spotty surface hoar in sheltered locations. Many recent avalanches have been reported on this layer, especially on southerly slopes around 1500-1800 m.
Additionally, several crusts in the mid/lower snowpack. Their depth ranges from 150 to 250 cm. The mid and lower pack is generally settled and bonded in thicker snowpack areas, with a lingering concern for these deeper buried interfaces in shallower snowpack areas.
Starry sky with increasing clouds. South wind 5-15 km/hr. Treeline low temperature -2 C. Freezing level 1200 m.
Mix of sun and cloud. Southeast wind increasing to 20-30 km/hr. Treeline high temperature +6 C, freezing level spiking around 2000 m.Monday
Increasing cloudiness, and light wet flurries later in the day. Southeast wind 10-30 km/hr. Treeline high temperature +2 C. Freezing level 1600 m.Tuesday
Light wet flurries and sunny breaks. Light northeast wind. Treeline high temperature +1 C. Freezing level 1500 m.
More details can be found in the Mountain Weather Forecast.
Terrain and Travel Advice
- Wind slabs may be poorly bonded to the underlying crust.
- Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet
- Pay attention to cornices and give them a wide berth when traveling on or below ridges.
Strong solar radiation and rising freezing levels will weaken the surface snow creating a wet loose avalanche hazard. Be mindful of overhead hazards like cornices.
Aspects: South East, South, South West, West.
Elevations: All elevations.
Where cold, dry snow prevails, recent southerly winds and up to 40 cm of the recent storm snow formed wind slabs on lee slopes. Recent snow was most reactive where it covers an older sun crust.
Aspects: North, North East, East, South East, North West.
Elevations: Alpine, Treeline.
There are several crusts in the mid-snowpack. Their depth ranges from 50-150+ cm and most likely found in thin snowpack areas or reloaded bed surfaces. A large trigger, such as a cornice fall or a smaller avalanche in motion, could trigger a very large avalanche on one of these deeply buried weak layers.
Glide slabs are unpredictable and may release during the warming.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Valid until: Mar 19th, 2023 4:00PM