Avalanche Forecast

Fair - Timing, track, or intensity of incoming weather system is uncertain

A weak storm system reaches the interior Monday night. Models are currently showing 5-10mm of precipitation for parts of the region ending Tuesday morning. During the storm pulse, alpine winds are forecast to be moderate from the SW and freezing levels should be between 1000 and 1500m. A ridge of high pressure builds in the wake of the storm and a mix of sun and cloud is expected for Tuesday afternoon. Alpine winds are expected to shift to the NW and remain moderate. On Wednesday, mostly sunny conditions are expected with light SW winds in the alpine. Freezing levels are forecast to be around 1200m in the morning and 2000m in the afternoon. Another storm pulse is expected to reach the interior on Wednesday night and should bring light precipitation for Thursday.

On Sunday, natural avalanches up to size 2.5 were reported.  Slabs were typically 30-50cm thick and were occurring above 2000m elevation.  Two remotely triggered avalanches have been reported and were triggered from up to 30m away. These remote triggers as well as reports of whumphing and wide propagations are suggesting that the weak layer below the storm snow is very reactive in some areas.  On Saturday, isolated natural avalanche activity was reported up to size 2 and skiers/explosives triggered avalanches up to size 1.5. On Tuesday, lingering storm slabs are expected to be reactive to human-triggering, especially in steep alpine terrain and wind-loaded terrain features. If the sun is out in the afternoon, natural avalanche activity is expected and extra caution should be given to steep sun-exposed slopes.

20-60cm of recent snowfall overlies a weak layer that was buried on Friday. This weak layer typically consists of surface hoar and facets overlying a melt-freeze crust that exists everywhere except high elevation north-facing terrain. Recent snowfall amounts are highest in the north of the region and taper off to south. In exposed alpine terrain, strong SW winds have redistributed the recent storm snow forming thicker wind slabs in leeward features. Large cornices exist in the alpine and may become weak with daytime warming. There are three dormant persistent weak layers that we are continuing to track. The late-March crust is down 50-70cm and was reactive last week during the warm period. The mid-March and mid-February layers are typically down between 70 and 100cm and have been dormant for several weeks. These layers have the potential to wake up with sustained warming, a significant rain event, and/or a big cornice fall.