Summary
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain
Weather Forecast
After the storm clears a westerly zonal flow pattern with short lived disturbances is expected for Monday & Tuesday. That means westerly (upslope) regions should see the bulk of the precipitation (around 10 - 20 cm daily in favoured areas), moderate SW winds, and freezing levels around 1000 m on Monday and a little higher (warmer) on Tuesday. Wednesday the pattern is set to change as a ridge builds and dries out the area with warming temperatures. Thursday freezing level is expected to be around treeline (2000mis possible).
Avalanche Summary
Few avalanches reported Saturday; limited visibility restricted observations. Professionals working in the area expect today (Sunday) to have a widespread natural avalanche cycle including large full-path avalanches running from alpine to valley bottom, large windslabs at treeline and alpine elevations (to around size 2.5), widespread storm snow avalanches (independent of wind-loading) at all elevations, and possibly even deep releases at treeline and below treeline elevations on the deeply buried facet & crust combination. Looking forward to Monday I expect natural activity will taper off but will not have fully stopped and conditions will remain primed for human-triggered slides, which could be large. I would continue to remain very suspicous of cornices and the possibility of cornice triggered slides.
Snowpack Summary
Around 40 to 60 cm of new snow in the past 24 hours and storm snow totals of 150 cm or more are reported. Mod southerly or southwesterly winds have created windslabs and large fragile cornices. Warm temperatures are promoting storm slabs in the short term (upside down storm snow layers) and settling (strengthening) in the slightly longer term. All this new snow increases the load (stress) on deeper layers created during the mid-January cold snap; namely facets (sugar) and a crust at lower elevations (say 1500m and lower). This layer is now deeply buried (around 200 cm or more in many places) but snowpack test results on this layer range from no result to easy (variable strength) but the shear pops (if triggered it wants to propagate).
istorm,
Avalanche Canada
