A strong southeast storm system will bring more snow Thursday night. Amounts are uncertain but accumulations of more than 30 cm may be possible by Friday. This along with wind will form touchy storm slabs at upper elevations.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
TONIGHT: Snow. Accumulation 10-15 cm. Ridge wind moderate, east. Temperature near -8. Freezing level lowering to valley bottom.FRIDAY: Snow. Accumulation 10-20 cm. Ridge wind light, northeast. Temperature near -3. Freezing level 800 m.SATURDAY: Mainly cloudy, light flurries. Accumulation 2-5 cm. Ridge wind light, east. Temperature near -4. Freezing level 600 m.SUNDAY: Mix of sun and cloud. Ridge wind light, east. Temperature near -6. Freezing level 500 m.
Avalanche Summary
Storm snow has grown touchy cornices and formed widespread soft storm slabs near ridge tops and open areas at treeline and below. On Wednesday there were reports of several natural and skier triggered size 1 loose, dry storm snow releases on all aspects above 1700 m, as well as a few size 2-2.5 natural storm slab releases on northeast aspects that where possibly cornice triggered.Tuesday a size 2.5 natural storm slab release that was likely triggered by a cornice collapse, was reported on a northerly aspect in the alpine. Cornice collapses up to size 1.5 were also reported but did not produce slab releases on the slopes below.Numerous wind slabs up to size 2 and loose dry avalanches up to size 1.5 were reported from the Lizard Range on Monday running either naturally or triggered by skiers testing small slopes. Explosives triggered widespread storm slabs up to size 1.5 and size 2 results on northerly aspects. Crown depths typically ranged from 40-80 cm.
Snowpack Summary
Approximately 40-70 cm of light dry snow has fallen in during the past week. This storm snow overlies various old surfaces including old hard wind slabs, crusts, facets and spotty surface hoar. Also in the upper to mid snowpack, a surface hoar layer buried mid-February is now 80 to 100 cm below the surface on sheltered northerly aspects.Deeper in the snowpack, the widespread mid-December weak layer sits about 200 cm deep. This consists of a crust, facets or surface hoar.Near the base of the snowpack, a crust/facet layer could be awoken from a thin-spot trigger point, or with a very large load like a cornice fall.
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.