Warm, wet, and windy! The storm will cause High avalanche danger for the next few days.
Confidence
Fair - Forecast snowfall amounts are uncertain on Wednesday
Weather Forecast
Overnight and Wednesday: A strong Westerly flow will continue to bring moderate to heavy precipitation and strong West-Southwest winds overnight and during the day. Freezing level rising to 1600 metres.Thursday:Continued moderate to heavy precipitation and strong Southwest winds. Freezing level at 1600 metres.Friday: The precipitation is expected to taper off as the Westerly flow weakens.
Avalanche Summary
Some thin wind slab avalanches were reported from Monday. I suspect that poor visibility and travel conditions will limit observations from Tuesday.
Snowpack Summary
A new storm slab is developing due to strong Southwest winds, new snow, and warming temperatures. The new storm snow has buried a thin layer of new snow and wind transported snow that is covering a widespread layer of surface hoar that developed during the recent clear weather. Sun crusts also developed during the clear weather on solar aspects up to about 2000 metres. Some areas had strong winds before the surface hoar was buried, so the distribution may be specific to sheltered and shaded terrain features. There is still concern for the buried weak layer of surface hoar from February 12th that is now down more than a metre in most places. The forecast new load of snow and wind may overload this deeply buried weak layer in areas that did not slide after the last storm.
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.
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.