 double-double seeking, snow-chasing, short-cutting, vertical feet collector
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Posted - 02/27/2004 : 9:56 PM
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February 27, 2004
This Forecast Sponsored by The North Face
South Coast Region
Weather: Snowfall this week was less than expected and mostly limited to high precipitation areas like Whistler, the North Shore, and the Coquihalla. Weather models predict a shift to a northerly pattern which means cooler temperatures, freezing levels at or below1000 m, light to moderate northerly winds, and some sun this weekend. Weather forecasters expect limited snowfall, primarily on Sunday when the next front arrives.
Snowpack: Recent new snow formed pillows of wind slab, primarily on northerly facing slopes behind windbreaks like ridge crests and rows of trees, or in gullies. Isolated pockets of these unstable slabs linger. The new snow rests on important old snow surfaces—sun crusts on southerly facing slopes, and two buried surface hoar layers in terrain protected from the wind. These surface hoar layers remain under the watchful eye of snow professionals.
Avalanche Activity: Numerous accidental & controlled avalanches to size 1.5 (a size 2 is large enough to injure, bury, or kill a person) were triggered Wednesday. These avalanches occurred in wind exposed terrain where southerly winds built pillows of wind slab. Few avalanches have been reported since Wednesday.
Forecast of Avalanche Danger Up To Monday Evening (February 27, 2004)
Alpine – Moderate
Treeline – Moderate
Below Treeline – Low
Travel Advisory: A great weekend is shaping up with a reasonable weather forecast, quality snow, easy trail breaking for skiers, good traction for sledders, and a manageable avalanche danger. To manage this danger select routes with care, monitor the effects of the sun on southerly facing slopes and any cornices above you, and maintain good avalanche habits. Good habits include: riding the line one at a time, stopping in a safe spot, having an escape route should things go wrong, and watching your buddies.
North Columbia Region
Weather: The past few days were warm and mostly wind free, with a mixture of sun and cloud. Up to 20 cm of snow refreshed the landscape in southern areas of the region. Looking forward, weather models and forecasters predict clearing skies Saturday afternoon and a northwest pattern developing Sunday. With the NW winds expect cooler temperatures, a mixture of sun and clouds, but little in the way of new snow.
Snowpack: Two weak surface hoar layers from February 24th and Valentines Day are 20-50 cm deep and remain reactive to human triggering. On southerly slopes the new snow rests on a crust. The deeper snowpack is generally strong; however, a crust/facetted snow combination 75 cm deep continues to be watched by snow professionals, especially in areas with thin snow cover. Below 1500m, the upper snowpack is moist.
Avalanche Activity: Reports of controlled, accidental, and remotely triggered avalanches large enough to bury, injure, or kill a person continue to trickle in. These avalanches are confined to northerly facing slopes at treeline and low alpine elevations on slopes as gentle as 30 degrees running on surface hoar.
Forecast of Avalanche Danger Up To Monday Evening (February 27, 2004)
Alpine – Considerable
Treeline – Considerable
Below Treeline – Moderate
Travel Advisory: Surface hoar instabilities are persistent—don’t expect these layers to heal soon. Observers continue to report avalanches started by people accidentally. Safe travelling will remain challenging this weekend. Select good routes and be especially attentive about treeline and alpine terrain on northwest through east facing slopes. Think carefully before venturing onto large alpine terrain or slopes steeper than 35 degrees. As always go one at a time, be watched by your buddies, and stop only where safe.
South Columbia Region
Weather: The past few days were warm and mostly wind free, with a mixture of sun and cloud. The clouds delivered 10-20 cm of new snow at higher elevations. Weather forecasters expect clearing skies Saturday afternoon and a northwest pattern to develop Sunday. With the NW winds expect cooler temperatures, a mixture of sun and clouds, and little in the way of new snow.
Snowpack: Two surface hoar layers 10-20 cm and 30-50 cm deep are the primary concern. Easy to moderate stability tests show this layer is susceptible to human triggering. Below the Valentines Day layer in the Purcell Mountains, a layer of facets from early January is still identifiable but has not been a factor in avalanches lately. Also in the Purcells, shallower snow depths are associated with a weak lower snowpack. Below 1800 m the snowpack is moist and at the lowest elevations is approaching a week isothermal state.
Avalanche Activity: Reports of controlled, accidental, and remotely triggered avalanches large enough to bury, injure, or kill a person continue to trickle in. These avalanches are confined to northerly facing slopes at treeline and low alpine elevations on slopes as gentle as 30 degrees running on surface hoar.
Forecast of Avalanche Danger Up To Monday Evening (February 27, 2004)
Alpine – Considerable
Treeline – Considerable
Below Treeline – Moderate
Travel Advisory: People continue to trigger avalanches. Safe travel this weekend will require good route selection, and careful evaluation when dealing with treeline and alpine terrain on northwest through east facing slopes. Think carefully about going onto large alpine terrain or slopes steeper than 35 degrees. As always travel one at a time, plan your exit, have buddies watching, and stop only in safe locations.
Kootenay Boundary Region
Weather: The weather picture for the weekend includes cloudy skies, light snow, and light to moderate winds. Temperatures will dip 5 degrees on Sunday as the wind shifts to the NW and cool air moves in from the north.
Snowpack: Warm temperatures caused slab conditions at treeline on Thursday. In the alpine, moderate and locally strong SW winds caused some windslabs to develop on N and E slopes. These slab layers lie on top of the two prominent surface hoar layers buried 10-20 cm and 25-50 cm deep, a combination almost designed for human triggering of avalanches. Easy stability test results on both layers Friday underline this likelihood. South facing slopes have crusts in place of the surface hoar layers; observers report that these slopes are more stable.
Avalanche Activity: A close call on Thursday and another on Wednesday illustrate the danger. Both avalanches released on the February 14th surface hoar; they were 30-35 cm deep and occurred in alpine areas of the Selkirk Mountains. One was on a NE slope and one was on a NW slope. Avalanche activity was reported from the main ranges of the Selkirks, the Valhalla range and the Bonnington range on Thursday.
Forecast of Avalanche Danger Up To Monday Evening (March 1, 2004)
Alpine – High, becoming Considerable on Sunday
Treeline – High, becoming Considerable on Sunday
Below Treeline – Considerable (where snow is deep enough)
Travel Advisory: Understanding the variability of surface hoar layers is key. With buried surface hoar, experience shows us it is possible for adjacent slopes to have different strengths; avalanche trigger points may exist on one and not the other. For that matter, uniform slopes may have weak and strong spots so that the third or fourth person on a slope triggers an avalanche after the first two safely passed. Observers report that south facing terrain is less dangerous. Sledders in particular, may use this information to their advantage. By sticking to south facing terrain you will reduce your risk of triggering an avalanche.
South Rockies Region
Weather: Light amounts of snow are forecast this weekend. Occasional sunny breaks will punctuate cloudy skies. Temperatures will cool on Sunday by about 5 degrees as the wind shifts around to the NW. Until then, moderate SW winds could be strong enough to move around some snow in alpine areas.
Snowpack: Two layers of surface hoar are found in the top 50cm of the snowpack. The Valentines Day layer is 30-50 cm deep; observers report that it remains weak in pockets of terrain. Another layer of buried surface hoar is 5-20 cm below the surface, beneath a slab of denser snow. This widespread layer reacts easily to stability tests - another layer to think about as and when snow accumulates on top. Variations are dramatic in snow layering and depth between the Fernie area and places with lower snowpack such as Elkford and the Crownest Pass. Lower snowpack areas report a strong upper snowpack, no problems with the February 14th surface hoar were observed.
Avalanche Activity: Avalanche activity declined on Thursday, however a few skier and explosives triggered avalanches were observed around Fernie. In the absence of any significant snowfall over the weekend avalanche activity will decline some more. Human triggered avalanches are still probable around the Fernie area on the two layers of buried surface hoar; avalanches could be large if they release on the lower layer.
Forecast of Avalanche Danger Up To Monday Evening (March 1, 2004)
Alpine – Moderate areas of Considerable*
Treeline – Moderate areas of Considerable*
Below Treeline – Moderate
Travel Advisory: Avalanche danger in the region can be described as follows: the target is small but consequences of hitting a bull’s eye are high. *The place to watch for is the deeper snow area around Fernie. Variability is high and a key point to consider; adjacent slopes could react quite differently. Hotspots will persist on N, E and even W facing terrain.
February 26, 2004
This Avalanche Information Report Sponsored by Canadian Pacific Railway
North Rockies
Weather: Weather during the week of February 19-25 was warm, dry, and sunny. The only snow, other than a few flurries, arrived today, February 26. Sunny skies and southerly winds made for spring-like temperatures in the mountains most of the week. Above freezing temperatures were common in alpine areas during the day, while overnight lows were not colder than -10 C. Light to moderate (25-40 km/h) winds from the south and west were common. Looking forward, the weather forecast calls for light snow through tomorrow night (February 27) with accumulations near 10 cm expected. Locally heavier snowfall amounts could occur, primarily on the west side of the mountains. At this time the weekend looks dry and slightly cooler.
Snowpack: Observers report a generally well settled snowpack. Weather from February 20-26 was good news for the snowpack in general; temperatures just below freezing strengthened the snowpack while cloud cover limited the sun’s effect on south slopes. A surface hoar layer formed during the week, but the wind blew it away in many alpine locations. This layer and another layer of buried surface hoar15-25 cm deep is found in areas sheltered from the wind near treeline. By Wednesday the 25th slopes facing S and SW did receive enough sun during breaks in the clouds to form a crust at all elevations. Below 1400m observers reported a rain or temperature crust on all slopes. Looking deeper in the snowpack, we continue to receive reports of a weak layer of facets over crust about 60cm below the surface. This layer seems to be weakest where the snowpack is shallow, say less than 150 cm. In particularly shallow spots we suspect that the lower snowpack is quite weak and faceted, although we did not receive any new information since our last report.
Avalanche Activity: Although our network of field observers was limited this week, a few avalanches were reported. Two cornice falls reported Tuesday triggered avalanches on the east facing slopes below. Reports earlier in the week identified natural and controlled avalanches releasing in pockets of wind slab.
Current Avalanche Danger as of Thursday March 04, 2004.
This rating describes danger as of the current date, and is not a forecast of future avalanche conditions.
Alpine – Moderate
Treeline – Moderate
Below Treeline – Low
Travel Advisory: Travel conditions in the mountains should be great this weekend with easy trail breaking for skiers and good traction for sledders. If the sun appears and temperatures rise to spring-like levels, southerly facing slopes could warm up and become a safety concern. Signs that the hazard from wet snow avalanche is rising include: the snow surface becoming moist, you starting to sink in deeper, or pinwheels and snowballs rolling down the slope. These signs suggest it’s time to leave the area and head to cooler, shadier locations. Watch out for cornices, especially if they’re up in the sun getting warm and soft. Besides the obvious hazard of being crushed by a falling car-sized chunk of debris, a falling cornice can stress slopes below, releasing a large destructive avalanche running far down into the valley. Looking ahead, watch the upper layers of surface hoar; these layers are most likely found in wind protected open treeline areas. As new snow accumulates on these layers they may become more active, potentially releasing avalanches. Remember, it should be a great weekend to be out enjoying the mountains—the key is to stay safe while having fun. |
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February 27 Canadian Avalanche Association PAB
