Vancouver Island Avalanche Bulletin

Valid until April 30th 2010 or next update as conditions require.

DANGER RATINGS (Make sure you understand the danger level meanings)

Confidence: The forecast accuracy is diminished his time of year due to lack of field information. Our forecast product relies on weather data, visual scans with high power binoculars,  and weekly visits to the mountains. 

Weather can spike the Hazard 'for a period of time' ; such as  Sun, Rain, Snow, Wind, light cloud cover during day, which causes a green house effect.  Further warming problems develop when cloud over night can prevent freezing of the surface and high prolonged above freezing temperatures persist making the snowpack Slushy or ISO THERMAL.

• Wet loose surface avalanches. (Potential Natural Trigger)
• * Wind Slab in Alpine, on leeward aspects West, North and to East. (North and West Isle)
• Cornice Fall above 1600 m, North West North North East East aspects (potential large natural trigger).
• Wet New and Old slab and or deeper wet slab potentially stepping down into February or January layers.

Avalanche Behavior in Spring:  A couple of things do occur in the spring that are worth mentioning:

1. Change happens Fast:    One minute a supportive crust the next slush. Many scenarios are possible but expect rapid change in stability as the temperature and other localized factors influence.
2. Entrainment:      Snow once Isothermal can be picked up by the original starting zone snow or cornice piece, this is called 'Entrainment'. Entrainment potential increases as the snow looses strength and this process greatly increases the volume of snow in involved in an avalanche. 
3. Distance avalanches travel:      Higher water content snow in spring avalanches can exceed normal run outs. The path the debris follow is typically more confined and follows 'Drainage' type features and does not usually travel as fast.
4. Packs a punch:     High water content snow and older deeper layers of the snowpack will typically have a higher water content or density. This means that the debris is heavier, will likely be much harder to dig if it sets up hard (normal).
5. Random Natural triggers:     Avalanche activity may taper right off and lull you into over confidence and then wham! The random large natural trigger cornice or old slab lets go and more snow often releases with it.

Weather:

The past weekend weather was a

A winter storm followed by spring weather is expected for the Island over the next three to 5 days days. 30 cm snow is possible Monday into Tuesday with lighter flurries by Wednesday and partial clearing leading to warmer and sunnier with cloudy periods and occasional showers into next weekend.  The winds are South up to 70 K and relaxing Tuesday and swithing around from South to West as the flurries come in and out.  Freezing levels are 1500 m with snow expected above 1400 m. Generally cooler and 20 mm wetter on the North and West Island. 

Avalanche Activity:

Soggy new snow slid off steep and Solar aspects over the weekend. No reports.

Expect avalanche activity Tuesday with storm warming and high winds over night into Tuesday.

Snowpack:

Rain up to 30 mm may soak the pack below 1400m more snow will be added above that 20 to 50 cm by Tuesday

Surfaces below 1560 m are Melt Freeze and somewhat Isothermal. Rain channels are evident.  These surfaces could form hard smooth crust for any new snow or windslabs. Cornices below 1500 m are greatly rounded off. Solar aspects melting and pinwheeling during heat of day, refreezing over night some nights and higher up. Most slopes, elevations  melting surface during day.  Large triggers or some more heat could reactivate the February old snow layers, down 50 to 200 plus cm.

Terrain Discussion: 

Caution higher elevation cold aspects as winter is having a bit of a return Monday/Tuesday

Watch out forwarming by  mid week and more warming into the weekend.

Connect the dots! Example: could the cornice over there collapse, trigger the slope below, step down into firmer snow and propagate horizontally into the terrain you are on?

Travel Advisory: 

Travel is not advised Tuesday and with Extra Caution Wednesday into Thursday and Perhaps a bit lower by he weekend if it freezes over night.

General Spring time advice: Watch the temperatures and sun and back out before the heat sets in. This time of year the sun, rain and above freezing temperatures are common. This brings the possibility of rapid temperature increases and changes in the snow cover. Natural triggers such as cornice, tree bombs could be active at this time. Human Triggering is unlikely when frozen and possible to Probable if sudden or prolonged melting or rain occurs. Caution with Travel on or below cornices.   Caution Solar aspects during day warming. Keep good track of your surroundings as large natural triggers could start slides high above you or trigger and propagate  horizontally.

Outlook:

Wintry weather will bring in the week with 35+ cm Snow for the North and West Isle and lighter snow 20 to 25 for the East Van Isle all with Moderate winds starting South to South West and Working to the West over Tuesday and switching to West North West by Wednesday  Temperatures and sun will increase Thursdayday and more into weekend, especially on the South, Interior and East ranges. Freezing levels are approximate, +- 1400m and rising to 2000 m during the day by later in the week.