Avalanche Forecast

Issued: Nov 28th, 2018 4:24PM

The alpine rating is considerable, the treeline rating is moderate, and the below treeline rating is low. Known problems include Storm Slabs.

swerner, Avalanche Canada

Lizard-Flathead.

The snowpack will likely need more time to adjust to the recent load of storm snow. With few field observations, uncertainty exists around the buried, weak surface hoar layer. We suspect the potential for human triggered avalanches remain high.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

The forecast weather trend will start to stabilize as a high pressure system sets up through the forecast period. THURSDAY: Mostly cloudy with a trace of snow/ alpine temperatures near -3/ generally light winds from the West/ freezing level 1300mFRIDAY: Cloudy with new snow 5 cm/ alpine temperatures near -4/ ridgetop winds light from the West/ freezing levels 1300 mSATURDAY: Mix of sun and cloud/ alpine temperatures -4/ ridgetop winds light from the southwest/ Freezing levels near 1100 m

Avalanche Summary

A natural avalanche cycle occurred yesterday in response to the new storm snow that fell on Monday night. Avalanche control using explosives triggered several storm slabs up to size 2 from N-NE aspects 1700-2000 m. Natural avalanche activity will taper off as the weather pattern becomes more stable. However, the snowpack may need more time to adjust to this recent load and human triggered avalanches may be the name of the game.

Snowpack Summary

Up to 35 cm of recent storm snow fell Monday and Tuesday. This adds an additional load onto a recently formed layer of weak, feathery surface hoar. The distribution of this surface hoar layer is uncertain at this time but I suspect its mostly found on sheltered slopes in the alpine and at treeline. South and southwest winds are redistributing the new snow building deeper deposits on leeward terrain. A mixed layer of melt-freeze crusts and sugary facets sits near the base of the snowpack. The snowpack is deepest in the alpine. At treeline the average snowpack depths are 80 cm. These depths taper rapidly at lower elevations.

Problems

Storm Slabs

35 cm of storm snow fell earlier this week building reactive storm slabs. These slabs will likely remain sensitive to human triggering, especially where they sit above weak, feathery surface hoar crystals or where the snowpack has seen wind.

Be careful with wind loaded pockets, especially near ridge crests and roll-overs.Watch for signs of instability, such as whumphing, shooting cracks, and recent avalanches.If triggered the storm slabs may step down to deeper layers resulting in large avalanches.

Aspects: All aspects.

Elevations: Alpine, Treeline.

Likelihood

Possible - Likely

Expected Size

1 - 2

Valid until: Nov 29th, 2018 2:00PM