Avalanche Forecast

Issued: Mar 28th, 2018 9:00AM

The alpine rating is moderate, the treeline rating is low, and the below treeline rating is low. Known problems include Wind Slabs and Loose Wet.

VIAC Bill Phipps, VIAC

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Vancouver Island.

Summary

Confidence

Moderate - Weather models in agreement as to timing, but type of precip (temp dependent) in question. Good field data on snowpack available.

Travel & Terrain Advice

Watch exposure during the warm parts of the day. In spring time, solar thawing and warmer temps will create wet surface instabilities faster than we expect and are used to as we emerge from winter. Even small loose wet sloughs have the force to push us into terrain traps and magnify potential injuries. Avoid travel and stopping above these traps, when exposed to large sun baked slopes in the heat of the day. These warm temps can also increase the fragility of cornices that grew over the winter. Be sure to give these overhangs a wide berth, while on top and when crossing below.A blast of storm/precip will take place Thursday, study what type of precip (snow, mixed precip or rain) falls at the different elevation bands (alpine, treeline and below treeline) and factor this into your decision making process as to what avalanche types you will expect to encounter (storm/wind slab if it snows vs. loose wet if it is mixed precip or rain).

Avalanche Summary

No new avalanche activity reported for the forecast region.

Snowpack Summary

Well unfortunately it seams like only the northern portion of the forecast region saw a significant amount of new snow over the past forecast period. The Cain region saw approx 16 mm of precip, west Strathcona saw around 8 mm and the east saw only 3 mm (rough conversion 1 mm of precip is approximately equal to 1 cm of snow if conditions (temps) permit). This new now sits on the previous moist storm snow which is bonding well to the old March 22 crust.

Snowpack Details

Surface: Moist new snow bonding well to previous storm snow. Upper: Moist prior storm snow well bonded to the March 22 crust. Mid: Well settled. Lower: Well settled.

Past Weather

Variable amounts of new snow (see snowpack summary), dependent on where you go in the forecast region. Winds were mainly light from the NW-SW. Temps were typical for what we expect in the spring time, cold overnight and warm (positive temps up into treeline elevations) during the day.

Weather Forecast

The forecast is for cloudy skies for this forecast period. A low pressure system will bring new precip to the area Thursday into Friday morning with the majority falling overnight. Strong SW winds will accompany the storm as well as a spike in freezing level at its climax. The type of precip that will fall and at what elevation will be the big question. Fingers crossed for snow!Wednesday: 0 to 4 mm of precip, winds light SW climbing to moderate, temps -4 to 0, freezing level 900 climbing to 1300 m.Thursday: 3 to 14 mm of precip, winds moderate SW climbing to strong, temps 0 to -1, freezing level 1000 to 1700 m.Friday: 0 to 6 mm of precip, winds moderate SW falling to light NW, temps 0 dropping to -2. freezing level 1300 to 260.

Problems

Wind Slabs

An icon showing Wind Slabs
Elevations and locations that see snow during Thursday-Fridays storm event will be exposed to strong winds from the SW. These winds (thought the snow will be warm, heavy and moist) will have some ability to move snow to lee aspects and crossloaded features, therefore resulting in possible wind slabs on N to W aspects. Expect these wind slabs to exist in the alpine and at treeline. These slabs will be possible, but unlikely to trigger naturally. With human activity it maybe possible to trigger these wind slabs, with the most likely spots in our typically prone terrain features (steep unsupported convex rolls). We can expect these avalanches to be size 1 to 1.5 in magnitude.

Aspects: North, North East, East.

Elevations: Alpine, Treeline.

Likelihood

Possible

Expected Size

1 - 1.5

Loose Wet

An icon showing Loose Wet
At elevations where the storms precip falls in the form of mixed precip or rain, we can expect to see some loose wet avalanche activity. Loose wet sloughs will possibly be seen at treeline and below on all aspects and typically from steeper terrain. We can expect them to be around size 1 to 1.5, will possibly triggered naturally and are likely to be initiated with human activity.

Aspects: All aspects.

Elevations: All elevations.

Likelihood

Likely

Expected Size

1 - 1.5

Valid until: Mar 30th, 2018 9:00AM

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