January 4, 2001 NOTICE OF UNUSUAL AVALANCHE CONDITIONS: Valid until further notice. This season avalanche professionals between the Inner Coast Mountains and the Rocky Mountains have observed snowpacks that are unusually weak. The combination of below normal snow depth and low temperatures has produced layers of facetted grains and surface hoar with a low strength. These types of weak layers can persist for a long time, and the avalanche danger will increase with every load of new snow onto this weak base. The present snowpack is less stable than in most other years and remarkably different from the snowpack at the same time last winter. Back country users will have to pay much attention to snowpack structure and strength during this winter. SOUTH COAST REGION WEATHER: The weather warmed up as predicted, although a cold front tracked through and caused a temporary dip below zero again. About 25cm of heavy storm snow fell in the alpine, while low elevation areas saw some rain. Winds were generally light, but became violently strong as the cold front came through. Lightning pounded the alpine during the frontal passage. The forecast calls for further warming, with the freezing line continuing to march upward. We may see rain to mid mountain by Sunday, and snow above. SNOWPACK: Lots happened in the last few days. The warming trend is overall promoting settlement and improving mid and lower snowpack pack stability. The storm snow and wind caused alpine wind slabs to form in lee areas, and these are still easily triggered. More snow will tend to make this worse in the short term. AVALANCHES: Mini-cycles of activity occurred during the rapid warming, and again with the wind event. Observations were somewhat limited due to the wind and lightning preventing access to the alpine. FORECAST OF AVALANCHE DANGER UP TO MONDAY EVENING (JAN 8 th) ALPINE ^Ö Considerable TREELINE ^Ö Considerable BELOW TREELINE ^Ö Considerable TRAVEL ADVISORY: The air mass is very unstable right now, making weather forecasters unsure if computer modeling is accurately predicting weather events. Regardless, the potential exists this weekend for both very rapid weather changes or locally intense moisture/wind events lasting a few hours. Keep your eye on the weather forecast in the morning, and the sky during the day, so you don^Òt get caught in the wrong place at the wrong time. NORTH COLUMBIA REGION WEATHER: The North Columbias warmed up and weather was pleasant, except Tuesday when a cold front ripped through, bringing high winds and locally variable snowfall at a rate of up to 3cm/hr. The net effect was up to 20cm of new snow in the alpine, falling as light rain below the 1500m elevation. The forecast calls for further warming and heavy moisture Friday, followed by light snowfalls through the weekend. A generally unstable air mass will produce locally violent storms combined with high variability in wind and moisture. SNOWPACK: The warming trend is promoting settlement, although Tuesday^Òs wind left a surface wind slab in some alpine areas. Three surface hoar layers down 25, 75, and 125cm are still producing shears. The lower facets are still weak and ugly, often producing a collapse as soon as the column is cut during snowpack tests. The low elevation snowpack is loosing strength generally due to the rain and warming AVALANCHES: Two large slides were observed on high glaciers breaking in the lower facets and running with the ice as the bedding plane. One slide in the Rogers Pass area was triggered by skiers and broke on the lower surface hoar down 125cm, propagating over a huge area. Activity to size 2 on the surface hoar down 25 was commonly observed. Near valley bottom, slides are running naturally, failing to ground due to warming. FORECAST OF AVALANCHE DANGER UP TO MONDAY EVENING (JAN 8 th) ALPINE ^Ö High, areas of Considerable TREELINE ^Ö High, areas of Considerable BELOW TREELINE ^Ö Considerable TRAVEL ADVISORY: With three buried surface hoar layers and the deep lower facets all recently reported active despite very few observations being available, conservative terrain continues to be of prime importance. SOUTH COLUMBIA REGION WEATHER: The South Columbias weather came in slightly delayed compared to the rest of the province, with the big winds from the cold front coming on Wednesday. Daytime highs reaching zero by Thursday, and winds were again light. Only 10cm of storm snow was reported. The weather forecast calls for further warming by Saturday, with little chance of moisture except the possibility of localized snow showers from convective cloud build-up. SNOWPACK: Snowpacks as shallow as 40cm at 2000m are still being reported, and throughout the region snow depth is below average. The warming has promoted settlement although Wednesdays wind loaded high elevation terrain features with a wind slab. Some surface hoar is surviving the warming and will likely be buried if we get some snow this weekend. The deep facets and depth hoar will be slower to improve. AVALANCHES: Few slides were observed, although observer activity is still limited by the shallow snowpack. Some slabs pulled out to size 1.5 due to cross loading from the wind. Whumfing is still commonly reported by people on skis or sleds, indicating with more snow further avalanche activity is likely. FORECAST OF AVALANCHE DANGER UP TO MONDAY EVENING (JAN 8 th) ALPINE ^Ö Moderate, Considerable in the Purcells TREELINE ^Ö Moderate, Considerable in the Purcells BELOW TREELINE ^Ö Considerable TRAVEL ADVISORY: Very few observers are operating, and some were not able to access the alpine due to wind as this bulletin was written. Expect to find high variability in conditions. In addition, weather forecasters report that the unstable atmospheric conditions make it likely the weather will be highly variable this weekend. ROCKIES REGION WEATHER: The weather was quite variable north to south, although a general warming trend occurred throughout. Up to 25cm of storm snow fell Wednesday at high elevations in the Mountain Parks, although some areas saw considerably less. More moisture for the weekend is in the forecast, falling as wet snow below treeline. Winds will remain out of the Southwest at 30 km/hr. Snowfall accumulation will be greatest in the northern parts of the area. SNOWPACK: Virtually the entire snowpack is still primarily weak facets and depth hoar. The storm snow and the new snow from the weekend will be forming a fat wind slab at the top of the pack. Many areas still report ski penetration well into the lower facet layers. AVALANCHES: A cycle of activity occurred in areas that saw snow mid week, although so little snow is available that sizes were reported only to 2.5 or less. More snow will extend the likelihood of slab avalanches failing at the storm snow interface. Virtually every avalanche will have the potential for stepping down into the lower snowpack weakness, growing in size and potentially propagating widely if it does. FORECAST OF AVALANCHE DANGER UP TO MONDAY EVENING (JAN 8 th) ALPINE ^Ö Considerable TREELINE ^Ö Considerable BELOW TREELINE ^Ö Moderate TRAVEL ADVISORY: If more snow arrives than forecasters predicted, expect avalanche danger to increase as well. With this storm snow from mid week available for wind transport, hazard will be creeping up as terrain features are loaded, even in the absence of any significant snowfall. Avalanche Awareness Days is January 12th and 13th. Check your favourite resort for local activities planned. It^Òs often a great way to learn a bit more about avalanches and show your support for this public bulletin.