Purcells

Fair - Due to variable weather conditions

Small fast moving systems are notoriously hard to forecast & to be honest, weather models do a poor job of handling them. As a result, I don't have a whole lot of confidence in this weather forecast. Take it with a grain of salt and be ready for changing conditions. Thursday evening: As the front exits to the east the region should pick up a few cm before winds diminish under clearing skies. Friday: A weakening low pressure system crosses over the region which in theory leaves 5 - 15 cm of snowfall in its wake. High pressure builds in after lunch offering sunny periods. Treeline winds light out of the S. Freezing levels start near 1200m, rises to 1600m with good recovery Saturday night. Saturday: The ridge of high pressure intensifies offering lots of sun to the region. There may be an occasional flurry, it is spring after all. Treeline winds very light. Saturday's freezing level starts near the surface and tops out near 1000 m, although I wouldn't be surprised to see that number climb as high as 1200 m with forecasted strong solar input. Sunday: High pressure continues to dominate the region ahead of what looks to be a fairly well organized system that *should* impact the coast. Sunday treeline winds 30km/h out of the W.

Very little avalanche activity in the region Wednesday, just loose snow avalanches to size 1.5 from steep rocky terrain. There are some reports of touchy wind slabs 20 cm in depth too.I've left some of the narrative in from last week as it offers a humbling look into the deep slab avalanche problem: On Friday, a very large avalanche was triggered by a cornice in Gorman Lake (Dogtooth Range). It was wide, deep and covered sled tracks. Photos here: https://bit.ly/GMOYCv . There were four other close calls in the Purcell Mountains last week, all involving very large slabs releasing either from a distance or with a light load. On Thursday, a snowmobiler remotely triggered a size 3.5 slab on an east aspect at 2400m at Oldman Creek, east of Quartz Creek (video here https://bit.ly/GLHIbg). It failed 1-2 m deep, was 200-300 m wide and ran full path, taking out mature timber. A second slope also failed, either remotely or sympathetically.

10 - 20 cm of snow has fallen in the last 48 hours, as of Thursday afternoon. In wind exposed locations this new snow has been formed into soft wind slabs 15 - 30 cm in depth. Below this lies a well settled snowpack. Spring the season has arrived, operators reported moist snow as high as 2500m on Wednesday. These warm temps have really helped to settle out the upper snowpack. Professionals throughout the region are reporting a very well settled & firm upper snowpack with minimum concerns in the upper 150cm.The exception is slopes below 1000 meters, which have not refrozen for many days. These slopes received as much as 10mm of rain Wednesday night making them rain soaked and sloppy. The sun is forecast to make an appearance Friday afternoon & will dominate skies on Saturday. The spring sun is increasing in strength as each day grows by a few minutes. It takes very little time for S, SE & SW aspects to feel the heat of the sun now. W & E facing slopes are just starting to be affected by the sun as we head into the tail end of March. As soon as the sun comes out, watch for roller-balling & pin-wheeling to start surprisingly quickly. Wet point release avalanches won't be far behind on slopes receiving direct sun.There's a lot of strong snow between recreationists and the February surface hoar layers and there hasn't been a deep slab avalanche since Saturday March 24th. Deep slab avalanches till may be possible. I'm thinking of two different scenarios at the moment:1. The most likely scenario is a large cornice or icefall failure impacting the slope below and producing a very large avalanche. Managing this piece of the hazard puzzle is done by monitoring what's happening above you. Cornices or slopes receiving direct sun are suspect. If you feel like there's a question as to whether or not a piece of cornice is warming to its breaking point, then, there's no question, it's time to get off that slope. Pay special attention to this this phenomenon on Saturday.2. Last weekend an experienced party remote triggered a very large avalanche in Glacier Park near Mt. Tupper. At this point I think the probability of human triggering the deep slab is very low. I don't really want to be proved wrong though, as the result would be large and destructive avalanche 1.5 - 2 m in depth. The most likely location for this type of failure is where the snowpack goes from thick to thin. This is most likely near ridge crests, the edges of slopes and especially around rock outcroppings.