Summary
Confidence
Fair - Freezing levels are uncertain on Tuesday
Weather Forecast
A ridge of high pressure intensifies over the region through the forecast period culminating with a significant warm up on Tuesday. Sun interrupted by periods of convective snow flurries continue for Sunday & Monday. Sunday: Freezing level starts near the surface, climbs to around 2000 m and then returns to the surface overnight. Ridge top winds light out of the north, winds quickly diminish at lower elevations. Monday: Upper level flow switches from northerly to a more mild southerly in the AM setting the stage for a very warm Tuesday. Freezing levels start near the surface, climb to around 2000m and then return again to the surface; the classic spring diurnal temperature swing. Winds should be light to moderate with an easterly component at lower elevations, switching to a light southerly at ridge top. Tuesday: Looks to offer the most significant warm up the region has seen yet this spring. Freezing levels start near the surface and then climb to 2800 m. Winds should be light southerly at all elevations.
Avalanche Summary
Wednesday's storm snow is now fairly well settled which has scaled avalanche activity way back, although solar aspects above 2000m produced several avalanches to size 1.5 as snow turned moist in the afternoon sun.
Snowpack Summary
Mild temperature continue to drive rapid settlement of Wednesdays storm snow. A sun crust is in place on slopes that face SW, S & SE. Dry snow can be found on due north facing slopes down to around 1400m. Around 30 cm of snow fell Wednesday accompanied by moderate southwest winds which brings total snowfall since March 26th to 120 cm. This snow rests on a suncrust on solar aspects and a melt freeze crust on non solar aspects below 2000m. On N aspects, shears within the upper storm snow are tightening with the persistent warm temperatures, although a reactive layer down 40-50cm remains. The March 26 interface consists of a melt/freeze crust down around 100cm, on all aspects except true north treeline and alpine, where small surface hoar (5mm) is present in sheltered places. The bond at this interface is gaining strength, with lingering concerns on true south aspects where the crust is thickest and where the surface hoar lurks. At lower elevations, the consistent high freezing levels have kept the new snow heavy and moist. The deep, persistent early February surface hoar lingers in the snowpack giving sudden results in testing. Concern remains with heavy triggers (cornice), step down avalanches and rapid loading from intense precipitation, strong winds or sun.
ghelgeson,
Avalanche Canada
