South Rockies

Fair - Freezing levels are uncertain

FRI: Skies should clear overnight Thursday into Friday. Cloud cover will increase Friday afternoon as a large Pacific warm front ambles into the region. The warm air mass will lift freezing levels as high as 1300m Friday afternoon. SAT: The jet is directing the bulk of the storm north of the region; as a result the So.Rockies largely miss out on significant precip. I expect only a few cm's on Saturday. Freezing levels (FZLZL) start out around 1000m on Saturday, climbing to 2000m in the late afternoon, so there is potential for rain on snow at upper elevations. Not much temperature recovery is forecast for Saturday night as FZLVL remain near 1800 m overnight. FZLVL's climb to 2100m Sunday as a strong Chinook wind develops on the east slope of the rockies. Mon: FZLZL dive back down to the surface as a cold front moves over the region. 2km WIND: FRI: Mod NW increasing to Strong NW in the afternoon. SAT: Strong to Extreme W. SUN: Strong to Extreme W.

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.