Avalanche Forecast
Regions: Lizard-Flathead.
It's incredibly difficult to forecast what will happen with dramatic warming and sun. Potentially large cornice failure and loose wet avalanche activity is likely to be widespread, probably best to avoid avalanche terrain Monday as the snowpack feels the heat for the first time.
Confidence
Low - Uncertainty is due to how the snowpack will react to the forecast weather. Uncertainty is due to rapidly fluctuating freezing levels. Uncertainty is due to the timing or intensity of solar radiation and its effect on the snowpack.
Weather Forecast
Warm air invades the region Monday pushing the temperature to near zero from valley bottom all the way up to 2500 m with just a few clouds and strong southwest wind. Tuesday and Wednesday are still warm with the freezing level hanging out around 1500 m.
SUNDAY NIGHT: Freezing level at valley bottom, moderate to strong west/southwest wind, trace of snow possible.
MONDAY: A few clouds at dawn with clear skies in the afternoon, air temperature warming to near 0 C as high as 2500 m, light southwest wind at lower elevations, strong southwest wind at ridgetop, no significant precipitation. Freezing level returning to valley bottom Monday Night.
TUESDAY: Broken cloud cover, freezing level rising from valley bottom to about 1500 m, light southwest wind at lower elevations, strong southwest wind at ridgetop, 1 to 3 cm of snow possible at upper elevations with potential for light rain down low.
WEDNESDAY: Broken cloud cover at dawn with scattered cloud cover in the afternoon, light west wind at valley bottom with strong west/northwest wind at ridgetop, trace of precipitation possible.
Avalanche Summary
On Saturday control work produced shallow size one avalanches up to 10 cm in depth.Â
On Friday, a widespread natural storm slab cycle was observed as size 1.5 to 2.5 storm slabs ran.
Looking forward, solar triggering of new snow can be expected amid sun exposure and warming temperatures, especially on steep south facing slopes.Â
Snowpack Summary
On Sunday a thin breakable rain crust was observed on the snow surface. Previous to this the region has received about 65 cm of snow in the last four days and almost 120 cm of snow in the last week. The recent storm snow is deep, soft and settling in the mild temperatures. Slight wind affect may be observed in exposed alpine features.
Several crust layers exist in the mid snowpack as a result of previous warming and rain events. These have not been identified as bed surfaces or failure planes in recent avalanche activity.
The bottom 10-20 cm of the snowpack consists of faceted snow and decomposing crusts. Although inherently weak, this basal layer has not been an active avalanche problem in our region for several weeks.
Terrain and Travel
- Minimize overhead exposure; avalanches triggered by warming or cornice fall may be large and destructive.
- The more the snowpack warms-up and weakens, the more conservative you`ll want to be with your terrain selection.
- Loose avalanches may start small but they can grow and push you into dangerous terrain.
- Avoid exposure to sunny slopes, especially in the afternoon.
Avalanche Problems
Loose Wet
Monday is going to be quite warm and sunny which is likely to initiate a loose wet avalanche cycle. Cornice failure could be a very serious hazard on Monday too. Once you start seeing roller balls and pinwheels loose wet avalanche activity is imminent.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Very Likely
Expected Size: 1.5 - 2.5
Storm Slabs
Sunny skies and warm temperatures may induce a fresh round of storm slab activity Monday as the settling storm snow feels the heat for the first time.
Aspects: All aspects.
Elevations: All elevations.
Likelihood: Possible - Likely
Expected Size: 1 - 2