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 Westerly winds overnight and during the day. Freezing level rising to 1900 metres.Thursday: Continued moderate to heavy precipitation and strong Westerly winds. Freezing level at 1700 metres.Friday: The precipitation is expected to taper off as the Westerly flow weakens.
Avalanche Summary
Some thin new wind slab releases were reported from Monday. Preliminary reports from some areas on Tuesday say that the new storm slab is very reactive, with widespread remote triggering and long propagations across terrain feature boundaries. There have been no reports of observations from the alpine due to poor visibility and travel conditions. The storm continues to develop and avalanche size and frequency is expected to increase.
Snowpack Summary
A warm and wet new storm slab is developing above a new surface hoar layer on shaded aspects and a sun crust on solar aspects. The new storm slab was reported to be very reactive today with avalanches up to size 1.5 triggered from remote locations and propagating long distances. The weak layer of surface hoar that was buried on February 12th is now down about 100-150 cm and was not triggered by cornice falls over the weekend. Some areas report that the February 12th surface hoar is rounding and getting harder to shear in snow profile tests, but continues to give planar shears when it does fail. The new load of storm snow may cause another cycle of natural activity on the February 12th weak layer.
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.