Avalanche Forecast
Issued: Jan 27th, 2021 4:00PM
The alpine rating is , the treeline rating is , and the below treeline rating is Known problems include Wind Slabs and Persistent Slabs.
cgarritty,
Avalanche Canada
Watch for small but touchy new wind slabs forming in the immediate lee of ridges and exposed terrain features. Monitor new snow amounts as you travel and be ready to manage a more widespread storm slab problem if you're in an area that sees more than 15 cm of new snow accumulate.
Summary
Confidence
Weather Forecast
Wednesday night: Cloudy with scattered flurries bringing 5-10 cm of new snow. Light to moderate southwest winds.
Thursday: Cloudy with continuing scattered flurries bringing another 5-10 cm of new snow. Light to moderate south or southwest winds. Alpine high temperatures around -8.
Friday: Mainly cloudy. Light variable winds. Alpine high temperatures around -11.
Saturday: Mainly cloudy. Light to moderate southwest winds, increasing over the day and overnight. Alpine high temperatures around -12.
Avalanche Summary
On Sunday in Glacier National Park, a skier triggered a size 2 avalanche upon entrance into a cross-loaded terrain feature.
We're continuing to track a layer of surface hoar from early January which is trending unreactive. Two MIN reports (MIN report 1; MIN report 2) from north of the region in Hope Creek report human-triggered slab activity from January 20. This MIN report from the Quartz zone (from Jan 14) shows a reactive layer of Jan 11th surface hoar on north-facing slopes near treeline. Investigate for this layer around sheltered treeline slopes where surface hoar has been preserved.
Following the mid-January storm, we received reports of avalanches reaching size 3 in the central part of the region, lending support to the idea that some larger releases may have involved more deeply buried persistent weak layers. Check out this MIN report from Mt McKay. Although avalanche activity on these layers from early December and November has been isolated, the possibility exists for large triggers to reactivate these deeper instabilities.
Snowpack Summary
Light flurries have begun to bury a layer of surface hoar recently reported in sheltered areas of the region howver gusty winds over the weekend likely damaged these crystals in more exposed upper elevations. Aside from this weak surface crystal, the new snow is burying a variety of surfaces including scoured and pressed surfaces in exposed terrain as well as more variable wind affected and facetted snow in sheltered terrain. A thin sun crust may be found on steep solar aspects.
A weak of layer of surface hoar from Jan 11th is down 10-50cm. In recent snowpack tests this layer has produced sudden results at treeline elevations in areas near KHMR. This persistent weak layer is most suspect in sheltered, open slopes at treeline and warrants slope-specific investigation if you're travelling in the north of the region.
Two deeper layers of surface hoar from December 13th and December 7th may still be found down 100-150 cm. The Dec 7th weak layer consists of a combination of decomposing surface hoar with a crust and faceted snow. Avalanche activity on these persistent weak layers has dwindled in the last week, with snowpack tests results trending to resistant and unreactive.
The lower snowpack is characterized by a notable rain crust from early November that is surrounded by a weak layer of sugary facets. It may still be possible to trigger with large loads in steep, shallow, rocky areas with a thin to thick snowpack.
Terrain and Travel
- Be careful with wind slabs, especially in steep, unsupported and/or convex terrain features.
- Storm slab size and sensitivity to triggering will likely increase through the day.
- Avoid shallow, rocky areas where the snowpack transitions from thick to thin.
Problems
Wind Slabs
10-20 cm of new snow is expected to accumulate in the region by the end of the day on Thursday. In most areas, new surface instabilities will likely be limited to leeward pockets loaded by wind. In higher snowfall areas to the south and west of the region, more widespread storm slabs may begin to form over a weak layer of surface hoar that is widespread in sheltered areas of the region.
Aspects: North, North East, East, West, North West.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Persistent Slabs
A weak layer of surface hoar buried Jan 11 buried 20-50 cm deep may be found on sheltered, open slopes near treeline in northern parts of the region. Deeper layers from early December and November can still be found in the snowpack and remain a cause for concern in thick to thin areas at upper elevations. Overall these layers are trending unreactive, however steep, rocky and shallow snowpack areas would be likely trigger areas.
Aspects: All aspects.
Elevations: Alpine, Treeline.
Likelihood
Expected Size
Valid until: Jan 28th, 2021 4:00PM
