Regions
Northwest Inland.
Tricky winter conditions exist at higher elevations. Localized solar radiation, snow and winds will destabilize the snowpack. Use a conservative approach to terrain and watch for signs of instabilities.
Confidence
Poor - Due to the number of field observations
Weather Forecast
The next pacific front hits the North and Central coast Thursday evening bringing anywhere from 2-10 mm. Lingering cloud, periods of sunshine and convective snowfall may occur on Friday. Ridgetop winds will be moderate from the West and freezing levels near 1000 m. Saturday and Sunday will be mostly cloudy with light precipitation. Ridgetop winds will be strong from West and freezing levels rising to 1100 m Saturday. Warm moist air will reach the North on Sunday and freezing levels will rise to 2300 m.
Avalanche Summary
No new avalanche observations have been reported. On Friday, touchy wind slabs and storm slabs are likely, especially in areas that receive higher snowfall amounts. If the sun pokes out, solar radiation will be strong and deteriorate the upper snowpack. Watch overhead hazards like cornices, solar triggered slab and loose wet avalanches.
Snowpack Summary
Recent storm snow has likely formed touchy storm slabs. Strong westerly winds have redistributed this new snow and has formed wind slabs on leeward slopes and behind terrain features. The lack of bond between the new wind slabs and storm slabs over the older snow surfaces buried on April 9 th (surface hoar, crusts and facets) are the primary concern. The March 25th surface hoar / crust layer is reportedly unreactive, however; with the new load of wind and snow this should remain on your radar as it may re-awaken. Large ripe cornices are also of concern and will be a problem with additional loading, especially when the sun and warm temperatures come back.
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.