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Thursday 18 April, 2013
It's spring time. That means it's the time when the Vancouver Island avalanche bulletin ceases three times weekly bulletins.
Many thanks to all the great sponsors who have kept this bulletin going. If you appreciate the bulletin then please go to our sponsors page and pass your appreciations on to these fine community members that make it possible. Many thanks also to the board of the Vancouver Island Avalanche Centre and to all who volunteer.
If you are interested in becoming a sponsor of the bulletin please contact us at forecaster@islandavalanchebulletin.com.
We will not issue further bulletins this spring unless we see a heightened hazard that compels us to issue an up date or warning. If you are planning spring trips do check back here to see if we have issued any updates or warnings and as always plan your trips carefully.
Below is some general advice for traveling in avalanche terrain at this time of year:
Spring avalanche danger patterns are generally quite predictable in that they relate largely to day time warming from rise in temperature and direct sun light. Danger is generally lower early in the day when temperatures are cool, the sun is not yet affecting slopes or cornices above, and a strong supportive melt-freeze crust exists. Danger increases as temperatures rise, solar radiation intensifies, and surface snow becomes wet or slushy. If wet snow does not freeze overnight or if it's raining, hazard can be up at any time of day.
Watch for snow becoming wet and slushy to more than about 5cm depth, pinwheeling, snowballing and small loose, wet snow point releases out of steep terrain and at rock outcrops. When you see these signs be prepared to change your planned route to a shadier aspect which has not yet melted or if that is not available stay out of avalanche terrain. Remember that wet snow avalanches can occur on lower angled slopes of 25 degrees or less.
Always keep an eye on what is above you. There are still many big cornices in the island mountains that are primed to fail as temperatures rise. These very heavy pieces of snow are a powerful hazard in their own right but they can also trigger an avalanche even if the place that you are lower on the slope feels cool at the time.
There is still snow in the forecast. When it does snow look for amounts of 20 to 30cm or more and be aware that this snow may not bond well initially to underlying crusts. Also watch for wind transporting new snow and creating slabs of greater depth in the lees and in cross loaded features.
While getting out early is generally the rule of thumb it is worth considering that the snow tends to be hard first thing in the day and that exposure on steep slopes could result in nasty falls on hard snow which could be especially dangerous if there are consequences below. Remember that terrain traps such as cliffs and trees are a danger not only in avalanches!
If you are tripping in the island alps this spring please send your observations to us at forecaster@islandavalanchebulletin.com.
The Canadian Avalanche Centre has some good general advice for travel at this time of year with links to educational tools if you go HERE.
Sunday April 14 2013
Valid until: Tuesday April 16th 2013
| Outlook | Sunday | Monday | Tuesday |
|---|---|---|---|
| Alpine | CONSIDERABLE | MODERATE | MODERATE |
| Treeline | MODERATE | LOW | LOW |
| Below Treeline | LOW | LOW | LOW |
Confidence: Good over all trend strong, again twice as much snow on the Western Mountains vs. the Northern or Eastern Peaks.
Past Weather: 11th 12th 13th April - Thursday - very light snow, cool all day and light South East to West. Friday - Some 5 cm to 15 accumulations. Some brisk wind from South West West or North West. Cool again below freezing. Saturday - Dry most places, with light winds variable South-West to North West a bit brisk and again cool.
Main Concerns: (Avalanche problems)
A Spring perspective: 'Spring avalanche danger rises and falls with the temperatures. If freezing temperatures occur over night things can stabilize or 'Recover'. If it does not refreeze the snow looses strength deeper and deeper making easy for a surface slough or deeper old layers to be triggered. Hanging Cornices and Snow Pillows in Steep Rocky Terrain can fail without warning and act as large triggers for avalanches on the slopes below. In the spring, at times like this, the snow is wet and dense and the Wet Loose slides can knock a person around even in small amounts.
Windslab - New Wind-slabs could form in this period with cooler temperatures snow and wind. Their distribution is West through North to East or anywhere else... at higher elevations as Re deposited snow transport is possible or may have already occurred. Old Wind slabs exist. Avalanches could be naturally triggered by rain high temperatures and or may be reactive to skiers. Avalanches to size 1.5 Destructive Scale are possible or large enough to injure or maybe kill a person. Some sliding layers could include smooth crusts and buried surface hoar.
New Snow - New snow at higher elevations and some preserved old snow sit over crusts. In the forecast period up to 12 cm of new snow may fall. Natural avalanche unlikely but human triggered possible on certain steeper slopes / aspects or sliding layers. Avalanche size small to Medium size 1 or large enough to injure a person. Some sliding layers could include smooth crusts Solar aspects and buried surface hoar Cool aspects. Watch for amounts over 15 cm.
Cornice Sun and rain and above freezing temperatures could destabilize Cornices. So far around here the Cornice failures have been mostly small but combined with terrain traps large enough to injure a person. In certain thin snowpack or thin-rocky terrain, rotted deeper snow layers are becoming more reactive too. Human triggering unlikely.
Weather Outlook:
Sunday - LIGHTENING forecast PM. Clouds and snow showers 6 - 10 cm snow. Winds 10 to 2o West South West. Freezing levels to 1000m falling over night to surface.
Monday - Clouds, snow flurries light amounts snow. Winds 10 to 20 from the West, North and East. Freezing levels to 1000m and cool over night.
Tuesday - Clearing some sun. Winds Moderate drop to light North North East. Freezing levels rising to 1500m lowering to 500m by eve.
Avalanche activity - Limited activity and reporting. Solar aspects a concern originating from rocky or thin snow pack areas worse at lower elevations... Some Glide cracks starting to show in steep terrain. Windslab somewhat reactive to testing.
Snowpack - New Wind Slab exists at higher elwevations and West to North aspects. A newer melt freeze crust is widespread at mid to high elevations, and in some areas faceting underneath. Recent snow fell on crusts with facets and perhaps surface hoar. Moderate somewhat sudden planar shears are more reactive on old/wet facets down 15 to 25 cm in those warm or thin areas. Watch for more than just new snow problems in two places: One in sunny aspects/or lower elevations and thinner snow-packs; as the thick crusts below the surface loose strength the old faceted layers under them may be willing to slide again, and the second place where old and new Wind Slabs or pillows sit at higher elevations on many aspects. These old and new Wind Slabs sit over the zippy (in some places) March 20 crust and could be reactivated.
Travel/Terrain Advise: "Test snow bridges and frozen lakes"
Sunday: Extra Caution in the Alpine due to new snow and wind. Don't stop or travel too much under large terrain, Cornices or steep rocky areas. Do not cut slopes above your friends. Expect variable snow surfaces; including crusts, moist snow. Extra Caution and avoiding steeper larger slopes, thin areas, cornices, and unsupported terrain. Slip and fall hazard may exist. Watch for winds creating redeposited wind slabs. Avoid COMPLEX terrain if it snow or blows much.
Monday: Watch for winds creating redeposited wind slabs. Extra Caution in the wind affected areas and in steeper terrain, thin rocky areas and unsupported terrain. Watch for overhead hazards. Slip and fall hazard may exist.
Tuesday: Watch for winds creating redeposited wind slabs. Caution in the wind affected areas and in steeper terrain, thin rocky areas and unsupported terrain. Watch for overhead hazards. Slip and fall hazard may exist. Watch Solar aspects and steep overhead terrain if sun is prolonged or temperatures make it to the teens.
Note: This may be one of the last detailed updates for the season; following this period we will run a generic spring message and provide updates if and when relevant. Good work people out there not getting injured too badly or killed in avalanches this season and providing good information and feedback. NW
Watch for updates to the bulletin, information on current conditions or observations on our Facebook page.
Prepared by: Niko Weis
Observations or comments? We want to hear them
Wednesday April 10 2013
Valid until: Saturday April 13th 2013
| Outlook | Wed/Thursday | Friday | Saturday |
|---|---|---|---|
| Alpine | CONSIDERABLE | CONSIDERABLE | CONSIDERABLE |
| Treeline | MODERATE | MODERATE | CONSIDERABLE |
| Below Treeline | MODERATE | LOW | MODERATE |
Confidence: Pretty good but really watch freezing levels especially if cooler and windier.
Past Weather: 8th 9th 10th April - Dry Monday with day time temperatures into the plus 4 or 12 if sunny. Mixed rain and snow Tuesday with better freezing levels than forecast some 5 cm accumulations. Tuesday eve storm drops 16 to 25 mm on the island and the storm lingers into Wednesday AM with 14 to 25 more mm rain or snow. Snow line at 4000 feet 1250 m Wednesday the front passed and the day dried out. Wind was a factor in the period high up. West to Northwest and switch to South East with last storm.
Main Concerns: (Avalanche problems)
A Spring perspective: 'Spring avalanche danger rises and falls with the temperatures. If freezing temperatures occur over night things can stabilize or 'Recover'. If it does not refreeze the snow looses strength deeper and deeper making easy for a surface slough or deeper old layers to be triggered. Hanging Cornices and Snow Pillows in Steep Rocky Terrain can fail without warning and act as large triggers for avalanches on the slopes below. In the spring, at times like this, the snow is wet and dense and the Wet Loose slides can knock a person around even in small amounts.
Windslab - New Wind-slabs could form in this period with cooler temperatures snow and wind. Their distribution is hard to predict as winds are unusual, but South East through North or anywhere else... at higher elevations. Old Wind slabs exist at higher elevations in the Alpine and on Leeward and Cross-loaded terrain on North-West to North through East aspects. Avalanches could be naturally triggered by rain and or may be reactive to skiers. Avalanches to size 2 Destructive Scale are possible or large enough to injure or kill a person. New and old Wind-Slabs could combine to form a larger slide.
Storm Slab - Friday Saturday - New snow at higher elevations and some preserved old snow sit over crusts. In the forecast period up to 40 cm of new snow may fall. Natural avalanche unlikely but human triggered likely on certain steeper slopes / aspects at higher elevations. Avalanche size small to Medium size 2 or large enough to injure or kill a person.
Loose Wet / Wet Slab - (At lower elevations and Solar aspects): Sun and rain and above freezing temperatures could destabilize the snow surfaces or deeper layers. Wet or moist snow falls out of steeper terrain on most aspects lower elevations. Skiers may trigger or cut down moist snow on slopes over 35 degrees. Avalanches will be mostly small but combined with terrain traps large enough to injure a person. In certain thin snowpack or thin-rocky terrain, rotted deeper snow layers are becoming more reactive.
Weather Outlook:
Thursday - Clouds and sunny periods. Light flurry possible. Winds 10 to 2o plus North West. Freezing levels to 1500m falling over night to 1000m.
Friday - Clouds, snow mid day 15 to 25 cm by eve. Winds moderate from the Southeast then West. Freezing levels to 1000m.
Saturday - Snow continued in early AM 10 - 15 cm more possible. The day improves though and cools and maybe clearing. Winds Moderate to Strong gusts from the South- East and switching later to Northwest lighter North. Freezing levels 1000m lowering to 500m by day time.
Avalanche activity - Limited activity. Pinwheels. Solar aspects a concern originating from rocky or thin snow pack areas worse at lower elevations... Some Glide cracks starting to show in steep terrain. Limited observations.
Snowpack - A newer melt freeze crust is widespread at mid to high elevations, and in some areas faceting underneath. New snow may fall on crusts with facets and perhaps surface hoar may form Wednesday or Thursday eves. At lower elevations; sun rain and prolonged above freezing temperatures have destabilized the snow surface and loosened up deeper layers. Moderate somewhat sudden planar shears are more reactive on old/wet facets down 15 to 25 cm in those areas. Watch for more than just new snow problems in two places: One in sunny aspects and thinner snow-packs; as the thick crusts below the surface loose strength the old faceted layers under them may be willing to slide again, and the second place where old and new Wind Slabs or pillows sit at higher elevations on many aspects. These slabs sit over the zippy march 20 crust and could be reactivated by new Wind-Slabs or Humans.
Travel/Terrain Advise: "Test snow bridges and frozen lakes"
Wednesday/Thursday: Don't stop or travel too much under large terrain, Cornices or steep rocky areas. Do not cut slopes above your friends. Expect variable snow surfaces; including crusts, moist or wet slushy snow. Extra Caution and avoiding larger slopes, thin areas, cornices, and unsupported terrain. Slip and fall hazard may exist. Watch for winds creating redeposited wind slabs.
Friday Saturday: Friday - Good in Am perhaps, watch for winds creating redeposited wind slabs.. Later in day travel gets dicey in the Alpine due to high winds and snow. Saturday - Caution in the wind affected areas and in steeper terrain, thin rocky areas and unsupported terrain. Limit use to SIMPLE or Low end Challenging terrain until Sunday. Do not cut slopes above your friends. Caution Improving weather in the PM could lure you out while Storm slab and Wind -Slabs could be reactive. Extra caution is recommended in the Alpine and wind affected areas.
General for period: Avoid steep thin snow pack areas on rocky ground cover at lower elevations during sun or rain and in general.
Watch for updates to the bulletin, information on current conditions or observations on our Facebook page.
Prepared by: Niko Weis
Observations or comments? We want to hear them
Important Notice
This bulletin covers the mountainous region of Vancouver Island from the Mt. Cain Ski Area in the North to the Beaufort range to the South including the mountains of Strathcona Provincial Park.
This is a regional forecast and significant variation may exist within the forecast area. The information and danger ratings are intended as a trip planning aid for recreational, backcountry users of avalanche terrain; they are not meant to be used as the sole factor in determining the avalanche danger presented by a specific slope.
Always include local weather, snowpack and avalanche observations in your decision to travel in avalanche terrain. Observations and experience may lead to different conclusions from what is reported or recommended. See disclaimer for further details. The technical data used to produce these bulletins is obtained from a variety of sources, including local ski areas and remote weather resources.