Purcells

Fair - Freezing levels are uncertain on Tuesday

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 3000 m. Winds should be light southerly at all elevations.

Control work in the region produced avalanches to size 3 on N through E aspects in the Dogtooth Range Friday. Natural avalanches were observed in the central & southern portions of the region on both shady and sunny slopes at upper elevations to size 3. In two separate instances cornice fall triggered large avalanches on NE facing slopes in the alpine, something that I suspect will continue through the holiday weekend.

Mild temperatures and intermittent solar radiation between breaks in convective snow flurries continue to settle out Wednesdays storm snow. Wednesday's system produced around 40 cm of new snow in the north & 25 cm in the south. The recent storms have added up to about a 125 cm of snow which rests on the March 27th interface. This layer displays itself as a sun crust on southerly aspects and a temperature crust on more northerly slopes. A thin layer of facets and or surface hoar can be found on this crust on all aspects. Operators are still reporting moderate shears on this interface. Cornices are reported to be very large and exist on most ridge lines. The mid-pack is well settled and strong. There is a weak layer of facets or depth hoar in shallower snowpack areas that may fail with initial warming of the snowpack. There is also a weak layer of of facets or depth hoar above a crust at higher elevations where there was already snow in October.