Regions
Northwest Coastal.
A number of weak layers will be tested by this storm, choose terrain defensively for the next few days. Ratings are based on significant snow accumulations on Thursday, if the storm is delayed until Thurs. night, ratings may be a touch over done.
Confidence
Poor - Timing of incoming weather systems is uncertain on Thursday
Weather Forecast
Synopsis: Warm air riding up and over the arctic air has created an above freezing layer at upper elevations that should stick around through Thursday morning. Looks like we swing back into the storm track Thursday night. Back to back storms through Tuesday should add some much needed volume to our snowpack. Thursday: Freezing Level: 800m, Precipitation: 4 to 10mm | 4 to 15cm; Wind: Treeline: Moderate W/SW | Ridgetop: Extreme, SW.Thursday Night: Precipitation: 5 to 15mm | 5 to 20cm.Friday: Freezing Level: 800m; Precipitation: 2 to 10mm | 2 to 15cm; Wind: Treeline: Strong, W | Ridgetop: Extreme, WSaturday: Freezing Level: Valley Bottom; Precipitation: 1 to 4mm | 1 to 5cm; Wind: Treeline: Moderate, NW | Ridgetop: Strong, NW.
Avalanche Summary
No new avalanche activity to report from Tuesday. On Monday wind and storm slabs to size 2.5 ran on NW, SW and SE facing aspects between 1500 and 2000m.
Snowpack Summary
Strong outflow winds on Dec. 28 left a variety of wind affected conditions in their wake in wind exposed terrain at all elevations. You will likely find wind pressed snow on north aspects, thicker wind slabs on south facing features and some degree of crossloading on everything else.At and below treeline widespread surface hoar has been reported which will likely be a player with the incoming storm system.The mid December crust can be found down around 30 to 80 cm and is sandwiched with facets and surface hoar.The mid November crust down 70 to 175 is gaining strength but is still reactive in test profiles. It is likely trending towards dormancy.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.