Avalanche Forecast

Archived

Mar 3rd, 2022–Mar 4th, 2022

Alpine

Natural avalanches possible, human triggered probable.

Treeline

Natural avalanches possible, human triggered probable.

Below Treeline

Natural avalanches unlikely, human triggered possible.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely, human triggered possible.

Below Treeline

Natural avalanches unlikely.

Alpine

Natural avalanches unlikely, human triggered possible.

Treeline

Natural avalanches unlikely.

Below Treeline

Natural avalanches unlikely.

Regions

Lizard-Flathead.

Choose simple terrain, and avoid exposing yourself to terrain traps. Snow and rain continue, and the wet surface snow may not freeze overnight.

Confidence

Moderate - Forecast precipitation (either snow or rain) amounts are uncertain. Uncertainty is due to difficult to forecast freezing levels. The snowpack structure is generally well understood.

Weather Forecast

Unstable airmass is causing uncertainty with the timing and intensity of convective showers into Friday.

Thursday Night: 2-10 cm of snow expected, but up to 20 cm possible due to convective flurries. Light to moderate southwest ridgetop winds. Freezing level between valley bottom and 1000 m, treeline low around -6 °C.

Friday: Cloudy in the morning, potential clearing in the afternoon. 0-5 cm of snow expected. Light variable wind. Freezing levels rise to 1300 m. Treeline high around -4 °C.

Saturday: Scattered clouds. No new snow expected. Light northeast ridgetop wind, trending to moderate at higher elevations. Freezing level at valley bottom overnight, rising to 1250 m through the day.

Sunday: Partly cloudy. Possible trace of snow expected. Light north ridgetop wind, trending to moderate at higher elevations. Freezing level at valley bottom overnight, rising to 1250 m through the day.

Avalanche Summary

On Thursday, there were reports of many small Loose Wet avalanches in steep terrain below tree line across the region.

Multiple professional operations have reported that visibility of alpine start zones has been poor, we expect that we will see more evidence of natural avalanches from this storm as the weather clears over the weekend.

On Wednesday morning storm slabs were still reactive to explosives and ski cuts in the size 1-2 range. A widespread storm slab avalanche cycle with size 2-3 avalanches on a variety of aspects and elevations was reported from the region on Tuesday. Check out this recent MIN report taken from within the ski area boundary looking out of bounds towards the Mammoth Droppings.

Snowpack Summary

Convective flurries could bring up to 20 cm of new snow overnight Thursday and through Friday. If these localized cells of precip miss your area, you could get none:(

The Lizard Range has received over 100 mm of water from this system which has translated to about 50-70 cm of heavy, upside down type snow at treeline elevation. Snow has generally been rain-soaked below 1600 m. Temperatures have been cool enough over night to start freezing some of this wet surface snow, but not cold enough to form a solid crust.

The recent storm snow sits on a variety of old surfaces like sun crusts, freezing rain crusts, old wind-pressed snow or cold, weak snow crystals on shaded aspects. Moderate to strong southwest winds have likely contributed to cornice growth as well.

Storm snow avalanches may step down to old persistent layers such as the surface hoar layer buried at the end of January. The distribution of this layer is spotty in nature but has produced avalanches and concerning snowpack test results in the past week, mostly in the Flathead. While it does not appear to be as widespread or reactive in the Lizard Range, it has been found in some locations.

The lower snowpack is well consolidated, with a crust/facet layer from early-December found near the bottom of the snowpack. It is currently considered dormant but with big rain on snow events, operators will be on guard. Check out the forecaster blog for more information.

Terrain and Travel

If you are increasing your exposure to avalanche terrain, do it gradually as you gather information.
Extra caution is needed around cornices under the current conditions.
Use small low consequence slopes to test the bond of the new snow.
Dial back your terrain choices if you are seeing more than 20 cm of new snow.
Be alert to conditions that change with elevation.
The more the snow feels like a slurpy, the more likely loose wet avalanches will become.

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.

Loose Wet

Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

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.