This bulletin is based on limited data. Local variations in conditions are likely to exist. Check out the Forecaster Blog for further details on interpreting early season bulletins.
Confidence
Poor - Due to limited field observations for the entire period
Weather Forecast
A Pacific frontal system is moving through the interior regions Friday and extending into Saturday. This will bring strong ridgetop winds, and light-moderate amounts of snow. After the front passes, a weak ridge of high pressure will push into the region bringing dryer, cooler, and clearing conditions that will last through the weekend. Freezing levels will stay in the valley bottom through the period.
Avalanche Summary
Reports of audible large avalanches were heard around the Harvey Pass zone yesterday. Several crowns were spotted on North through East aspects with wide propagation. If you and your friends have been out exploring and riding in the backcountry, and have some observations to share please send us an email to [email protected].
Snowpack Summary
Snowpack observations and information are extremely limited, and conditions across the region vary. Building storms slabs and wind slabs likely exist in the alpine and at treeline elevations. An early season (Nov 8) rain crust has been reported to exist around 2000 m and above on NW-NE aspects. A recent field test from the Harvey Pass area shows an ECTN 18 down 85 cm on top of the crust, ECTP22 down 75 cm on last weeks storm interface. In the alpine I suspect 100 + cm of snow, and treeline seeing an average around 90 cm. Below treeline snow levels could be reaching threshold.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.