Avalanche Forecast

Issued: Nov 27th, 2018 3:44PM

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

ghelgeson, Avalanche Canada

Sea To Sky.

As rain turns to snow in the alpine Tuesday night, storm slabs and cornices are expected to develop. Watch for changing conditions Wednesday, steady southwest wind may form human triggerable slabs.

Summary

Confidence

Low - Due to the number of field observations

Weather Forecast

The system that has brought over 50 mm of rain to the forecast region should offer one last pulse Tuesday night. Wednesday marks the start of what looks to be a pretty significant drying trend as cold air begins to descend from the Arctic. No significant precipitation is expected for the duration of the forecast period and it looks like there is potential for clear skies by Sunday.TUESDAY NIGHT: Freezing level around 1300 m, moderate to strong southwest wind, 5 to 20 cm of snow possible with rain in the valley bottoms.WEDNESDAY: Broken cloud cover, freezing level holding around 1300 m, moderate southwest wind, trace of precipitation possible.THURSDAY: Scattered cloud cover, freezing level around 1000 m, light northerly wind, no significant precipitation expected.FRIDAY: Scattered cloud cover, freezing level around 800 m, light variable wind, no significant precipitation expected.

Avalanche Summary

On Monday natural loose wet avalanches to size 1 were reported on steep cutbanks near treeline. Loose wet avalanches to size 1 were also skier triggered. Please submit any observations you have to the Mountain Information Network here,

Snowpack Summary

Monday's intense precipitation event rain-soaked the existing snowpack up to about 1800 m and left wet snow in place up to 2000 m. Strong to extreme wind on Monday and Tuesday likely created touchy storm slabs, cornices, and wind damaged snow in high elevation alpine terrain. The deepest snow is found at alpine elevations, with depths of 60 to 140 cm. See this report from Brew Lake and this report from Shovelnose Creek for an idea of recent conditions. Approximately 50 cm of new snow now lies above a thin rime ice lens formed last weekend. A thicker melt freeze crust can be found 75 to 90 cm below the surface. This crust may be associated with weak faceted crystals in some places where it lies close to the ground. This is most likely to cause problems in glaciated terrain or on smoother, high elevation slopes where the summer snow did not melt out.

Problems

Storm Slabs

5 to 20 cm of snow accompanied by strong southwest wind is possible in the alpine Tuesday night. Watch for the formation of fresh slabs which may be sensitive to human triggering throughout the day in wind exposed terrain.

Be cautious as you transition into wind affected terrain.Use caution in lee areas in the alpine, storm snow may form touchy slabs.The new snow will likely require a day to settle and stabilize.

Aspects: All aspects.

Elevations: Alpine.

Likelihood

Possible - Likely

Expected Size

1 - 2

Cornices

Cornices are expected to form on alpine ridgelines as the wind continues to blow as temperatures cool.

Stay well back from cornices when traveling on ridgelines.Do not travel on slopes that are exposed to cornices overhead.Extra caution needed around cornices with current conditions.

Aspects: North, North East, East, South East, North West.

Elevations: Alpine.

Likelihood

Possible

Expected Size

1 - 2

Valid until: Nov 28th, 2018 2:00PM