Lizard Range and Flathead Avalanche Forecast
Apr 17th, 2019 4:41PM
First warm, then rain. A one-two punch over the coming few days is expected to maintain active loose wet avalanche conditions while bringing a test to any slabs that haven't quite bonded to the crust.
Wednesday night: Mainly clear. Moderate to strong southwest winds. Freezing level remaining near 2300 metres.
Thursday: Mainly sunny with cloud increasing over the day and showers beginning in the evening. Moderate to strong southwest winds increasing over the day. Alpine high temperatures around +4 with freezing levels rising to 3000 metres and remaining elevated overnight.
Friday: Cloudy with light rain showers, increasing and transitioning to flurries in the alpine overnight. Moderate to strong southwest winds. Alpine high temperatures around +5 with freezing levels dropping from 3000 to 2500 metres over the day.
Saturday: Cloudy with continuing rain showers and the possibility of 10-15 cm of wet new snow accumulating in the alpine, including overnight accumulations. Light variable winds. Alpine high temperatures around 0 with freezing levels to 2000 metres.
On Sunday skier triggered avalanches were widespread on north through east facing slopes in the alpine and down into treeline too.
A natural avalanche cycle occurred Saturday night, the highlights were storm slabs up to size 2 on northeast facing alpine terrain around 1700 m. A natural cornice failure was observed from a north facing ridgeline which subsequently triggered a size 2.5 storm slab involving the new snow. Control work produced storm slabs to size 2. We received a great MIN report of a small storm slab from Saturday morning in the first hours of the storm.
New sun and temperature crusts are likely to be found on the surface on solar aspects and below the alpine, having formed above the 30 cm of dense snow from the past weekend's storm. In most areas, this storm snow sits above a widespread supportive crust.
North facing alpine terrain may still hold a cold, dry snowpack. High elevation north facing terrain also harbours a deeply buried layer of facets. Although unlikely, human triggering of persistent slabs on this layer may still be possible in rocky alpine terrain with shallow or variable snowpack depth.
Below treeline the snowpack has melted or is isothermal.
Sunny breaks and steadily rising temperatures are expected to maintain potential for loose wet avalanche activity. The likelihood of loose avalanches increases as temperatures warm throughout the day and while sun exposure is strong.
- Avoid sun exposed slopes when the solar radiation is strong, especially if snow is moist or wet.
- Areas sheltered from wind but exposed to sun will be the most prone to loose wet activity.
- A moist/wet snow surface, pinwheeling and natural avalanches all indicate a weakening snowpack.
Aspects:East, South East, South, South West, West.
About 30 cm of storm snow rests on a widespread crust. The bond at this crust is likely strengthening, but it remains in question. Meanwhile, wind loaded slabs on high north aspects will see their first punch of heat on Thursday.
- Avoid recently wind loaded features near ridge crests, roll-overs and in steep terrain.
- Look for signs of instability such as whumphing, shooting cracks, and recent avalanches.
- Wet slab releases may occur if poorly bonded slabs become moist with sun exposure and warming.
Valid until: Apr 18th, 2019 2:00PM