Watch for conditions that change with elevation. There may be significantly more storm snow at alpine elevations.
Confidence
Poor - Due to limited field observations for the entire period
Weather Forecast
Overnight and Saturday: The freezing level should start to drop down to near the valley bottoms after a cold front moves through to the East. Alpine winds should continue to be moderate from the SW with gusts to strong later in the day. Expect 5-10 mm of precipitation that should fall as snow in most of the region overnight, and another 5 mm during the day Saturday.Sunday: It should be cooler and drier with light winds during the day on Sunday. Expect -7.0 in the alpine, with light southerly winds.Monday: The next wave of moisture is expected to make its way inland from the coast during the day. Poor confidence in amounts and timing, stay tuned we should know more tomorrow.
Avalanche Summary
No recent avalanche observations. No signs of whumphing or cracking were observed in the Harvey Pass area.
Snowpack Summary
A report from near Harvey Pass tells us that there is about 25 cms of storm snow that is "damp" at treeline and the ski penetration is only about 20 cms. The November crust was found to be buried down about 60 cms and was associated with a layer of facets either directly above or below. Light winds were not transporting much snow in this area. Alpine elevations may be quite different, as most of the recent precipitation has fallen as snow. We are hoping that the storm snow will bond well as temperatures cool, this may still take a day or two.
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.