Avalanche Forecast

Good

An "almost pineapple" weather pattern is setup across the province, and while the neighboring regions to the north & west receive the full firehouse, the So. Rockies largely miss out on the precip, but make up for that with big wind and warming. SAT: Freezing Levels (FZLVL) at sunrise will be near 1100m, climbing to 2000m around lunch. 1.4mm SWE expected, so just a few cm's of snow at upper elevations, very light rain below 2000m. 2km wind: Strong, W Ridgetop winds extreme NW. SAT NIGHT: FZLVL drops to 1700m overnight. SUN: FZLVL near 2000m most of the day. Expect strong Chinook winds. Trace of precip expected. MON: Winds start the day out of the SW, strong and drop town to moderate values in the afternoon/evening. FZLVL starts near 1700 slowly dropping to 1500m around sunset, dropping further to the surface by Tuesday AM. 2.9mm precip forecast.

Our field team remoted a size 2 avalanche from the flats Wednesday. It's worth checking out the details of the incident report linked to this forecast as it illustrates just how tender the persistent slab problem is in the So. Rockies. This incident likely foreshadows a very tricky weekend where avalanches will be larger and easier to trigger.

60 - 90 cm of light density snow fell last weekend and another 10 - 15 cm fell Weds. night. This snow rests on the Feb. 08 Surface Hoar (SH) (as big as 20mm) which is still quite sensitive in this region. On Wednesday snowpit test profiles on a NW slope near 2000m in the Flathead sub-region revealed a Sudden Planar shear down 85 on the SH. Winds blew out of the SW at moderate speeds for a few hours Wednesday evening creating shallow wind slabs on lee aspects. Moving into the weekend, a few different processes will affect the snowpack; A: Strong to Extreme NW winds are forecast beginning Friday afternoon continuing through Sunday. B: The freezing level is forecast to climb to 1300 Friday. Saturday it will climb to 2000m and remain there overnight Saturday continuing through Sunday. C: There may even be a bit of rain at upper elevations as convective flurries pass overhead Saturday & Sunday. These three different inputs will rapidly change the properties of the storm slab, I expect a cycle of potentially large natural avalanches Sunday, maybe even as early as Saturday. Lingering concern remains for basal facets, particularly in shallower snowpack areas with steep, rocky start zones. Our field team was out in the Crowsnest Thursday where they observed a much stronger snowpack. The So. Rockies forecast is intended to give trends for the region as a whole, and as such, conditions will be vary between the different sub regions.