Rising freezing levels over the next few days will weaken the snowpack and increase the Avalanche Danger.
Summary
Confidence
Moderate - Timing or intensity of solar radiation is uncertain on Monday
Weather Forecast
On Sunday, expect up to 5mm of precipitation which should fall as rain at most elevations. On Monday and Tuesday the region will see increasingly clear skies as a dry ridge of high pressure develops. Freezing levels should rise from 500m to 2600m on Sunday, and then climb to 3600m for Monday and Tuesday. Ridgetop winds should remain moderate from the southwest on Sunday and Monday, and then become light on Tuesday.
Avalanche Summary
Explosives testing on Saturday produced storm slab avalanches to size 2.5 in alpine terrain. Although natural avalanche activity should taper off on Sunday, storm slabs may remain reactive to the weight of a rider. Looking further ahead, rising freezing levels and solar radiation on Monday should spark a round of loose wet avalanche activity on sun-exposed slopes. Warming will also increase the likelihood of triggering cornice falls, wet slabs and deep and destructive persistent slabs.
Snowpack Summary
On Friday between 60 and 100cm of new snow fell. Strong to extreme southwest winds shifted these accumulations into deep and dense storm slabs. Cornices were already large before the storm, and new growth is expected to be fragile. Where it still exists, the mid-January surface hoar layer may be found between 130 and 200 cm below the surface. The combination of ongoing heavy storm loading and warm temperatures has likely flushed out this weak layer in most areas. That said, warming and solar radiation forecast for the next few days may be what it takes to wake up this deep and destructive persistent weak layer.
jlammers,
Avalanche Canada
