Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain for the entire period
Weather Forecast
The same weather pattern we've been in for the last few days persists for the foreseeable future as the Gulf of Alaska continues to steer a cool & unsettled airmass over the province. Saturday: Patchy skies in the morning before a relatively weak low pressure system slides across the region after lunch. Strong winds at ridgetop, light winds treeline & below. Freezing level tops out at 1200m. 5 - 10 cm expected by Sunday morning. Sunday: Very light snowfall Sunday morning before skies clear in the afternoon. Freezing level again near 1200m. Winds drop down to 25km/h out of the W Sunday. Monday: Freezing level starts at the surface, climbing to near 1300m during the day. Winds at the low end of Moderate at ridgetop out of the S, SW. Light winds at and below treeline. No significant precip forecasted.
Avalanche Summary
Wind loaded slopes produced human triggered slab avalanches to size 1.5 Thursday. Many point release avalanches were reported from south & west facing terrain with avalanches to size 2.5. One natural size 3 was reported in the north of the region on a N-NE facing slope.
Snowpack Summary
30 - 40cm of new snow has fallen in the last 48 hours, as of Friday afternoon. In wind exposed locations this new snow has been formed into wind slabs 20 - 60 cm in depth. This snow rests on the March 28th temperature crust. At upper elevations the new snow is bonding poorly to the slick crust. At lower elevations the crust was moist at burial which created a more substantial bond.Spring the season has arrived, and it's not just calendar spring either, it's really felt different in the mountains recently. The snowpack is far from isothermic, but the mercury has climbed above 0 as high as 2500m over the last 7 days. 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. These slopes should tighten Friday night with a good overnight refreeze.The sun is forecast to make an appearance Saturday afternoon & will dominate skies on after lunch Sunday. 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.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.