Regions
Northwest Coastal.
Stormy weekend weather means wintery avalanche conditions. A quick shift in mind-set is required Monday when summer sunshine and temperatures arrive.
Weather Forecast
Strong SW flow hitting the region is very "pineapple" like. Freezing levels should remain relatively low (snow as low as 1000m) through mid-day Sunday and a fair amount of precipitation is expected through Sunday in the south (through Monday near Stewart). SUNDAY: Overcast skies, freezing level as low as 1200m in the morning but climbing to near 2000m by evening, 5 to 10 cm of snow, strong south wind. MONDAY: Mix of sun and cloud as the system clears out, precipitation ends, freezing level rises to around 2500 m, strong south winds. Northern areas (e.g. Stewart) still in the storm. TUESDAY: Sunny, dry, even warmer than Monday (freezing level touching 3000m), light southerly wind.
Avalanche Summary
No new observations to report; however, remember that we have very few eyes & ears still in the mountains.
Snowpack Summary
Mod to Strong S'ly winds able to redistribute HS & HST at high elevations, primarily in the northern and inland areas. Cooler temps in "cold zones" have locked up capping crust. HST storm- & wind-slab developing, when warm temps / sun return there will be a new supply for Loose Wet .Snow is falling at elevations above about 1000m. The moderate to strong southerly wind has likely formed fresh wind slabs and created new cornice growth. This storm snow buried a widespread melt-freeze crust thought to exist almost everywhere except possibly high elevation north facing terrain. Any old layers in the midpack or at the ground are dormant for now, and the snowpack may just gracefully melt away. However, these layers have the potential to wake up; the hottest weather of the year is expected in a few days which might test almost forgotten layers.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.