Avalanche Forecast Lizard Range and Flathead

Monday 4th February 2019

Avalanche Danger Ratings Mon 4th Feb 4:46PM Danger Ratings Alpine: Considerable Danger Ratings Treeline: Considerable Danger Ratings Below Treeline: Moderate Persistent Slabs Persistent Slabs Wind Slabs Wind Slabs

Avalanche Canada Forecaster: kdevine

Date Issued:

Valid Until:

The recent snow has added load to buried weak layers and may still be reactive to human triggers. Conservative terrain selection is recommended.

Confidence

Moderate -

Weather Forecast

MONDAY NIGHT - Clear with cloudy periods / northeast winds 10-15 km/h / alpine low temperature near -22TUESDAY - A mix of sun and cloud / northeast winds 10-15 km/h / alpine high temperature near -16WEDNESDAY - A mix of sun and cloud / northwest winds 10-15 km/h / alpine high temperature near -17THURSDAY - A mix of sun and cloud with isolated flurries / southwest winds, 15-35 km/h / alpine high temperature near -14

Avalanche Summary

Avalanche activity has slowed down. There were reports of several size 2 explosives triggered avalanches on Sunday. Recent test results suggest that the new snow has not bonded well to a persistent weak layer that was buried in mid-January. This layer is described below in the Snowpack Summary.Many large storm slab avalanches were triggered naturally, by skiers, and by explosives on Saturday. The avalanches likely released at the base of the storm snow as well as within the weak layer of surface hoar buried mid-January.

Snowpack Summary

Around 60 mm of precipitation fell on Friday with a freezing level at 1600 m. Above 1600 m, the precipitation fell as snow, which has been redistributed by northwest winds. It may sit on weak and feathery surface hoar crystals in shaded and sheltered areas. Below 1600 m, the precipitation fell as rain and froze into a melt-freeze crust.The mid-January layer of surface hoar or a crust is buried around 40 to 60 cm. The surface hoar is found on shaded and sheltered slopes and is most prominent between 1600 m and 1900 m. The melt-freeze crust is found on south aspects at all elevations.The remainder of the snowpack is generally well-settled. Thin snowpack areas, such as in the east of the region, may find weak and sugary faceted grains near the base of the snowpack.

Persistent Slabs Persistent Slabs

Likelihood

Possible

Expected Size

2 - 3

The recent storm snow is loading a weak layer of surface hoar or a crust. The surface hoar is likely best preserved in shaded and sheltered areas between 1600 m and 1900 m. The crust exists on southerly aspects at all elevations.

Watch for signs of instability such as whumpfing, cracking, or recent avalanches.Make observations and assess conditions continually as you travel.Be aware of the potential for wide propagation.

Aspects: All aspects.

Elevations: All elevations.

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Wind Slabs Wind Slabs

Likelihood

Possible

Expected Size

1 - 2

Recent snow above 1600 m has been redeposited with southwest winds that switched to northeast winds. The touchiest deposits will be in lee terrain depressions, particularly near ridges.

Use caution in freshly wind-loaded features, especially near ridge crests and in steep terrain.If triggered, wind slabs may step down to deeper layers resulting in large avalanches.Avoid open slopes and steep terrain, since wind slabs may not bond well to underlying layers.

Aspects: All aspects.

Elevations: Alpine, Treeline.

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