March 14, 2003 SOUTH COAST REGION WEATHER: A further 130 cm of storm snow had accumulated by Friday, accompanied by strong SW winds and mild temperatures. A series of short breaks in the weather Friday tried to entice folks out into the snow just before closing in and dumping more snow on them. The weather forecast calls for winds to increase to 100 km/hr from the SW Friday night, followed by a series of snow showers throughout the weekend. Temperatures will remain mild until at least Monday and winds will moderate slightly later in the weekend. SNOWPACK: The storm snow has settled rapidly but is still up to 110 cm thick on Friday. Below treeline, up to 35 cm of rain soaked snow is found at the surface. At the interface under the storm snow, a shear exists that is a common failure point for natural releases. No reports have made mention of any deeper layers being active. AVALANCHES: A second widespread cycle of avalanche activity occurred Thursday, with most natural releases happening on north facing slopes due to wind transport of storm snow. Observers reported high variability in sensitivity to human triggering Friday, with slopes that did not react to explosives failing down 90 cm when ski cut from the top. FORECAST OF AVALANCHE DANGER UP TO MONDAY EVENING (March 17th) ALPINE - High TREELINE - High BELOW TREELINE - Considerable TRAVEL ADVISORY: Continue to treat all big terrain with caution, particularly on north aspects. Although the frequency of natural activity will subside, the potential for human triggering is still huge for the weekend. Big open slopes in the 31 to 35 degree range may not have run naturally and may be very sensitive to triggers. NORTH COLUMBIA REGION WEATHER: After nearly a full week of high winds, continuous rain and snow, and temperatures above seasonal norms, we have seen a break in the pattern. The cloud ceiling retreated to near mountaintop Friday, with only occasional showers and relatively light winds. Weather forecasters predict another strong low pressure system is heading onshore this weekend, leading to continued warm weather, more snow in the alpine and rain below. SNOWPACK: The storm snow varies in depth from 75 to 150 cm depending on elevation. At low elevations, the snowpack surface is wet down at least 25 cm and deeper in many areas. Some easy shears were found in the storm snow Friday, but these will quickly disappear. The interface under the storm snow, and the deeper crusts and buried surface hoar weaknesses, are seriously overloaded by all this recent snow, with up to 150 kg of weight added to every square meter of snowpack surface. The November crust is once again active and failing. AVALANCHES: Observers were finally able to get out in the field Thursday afternoon and Friday. They report a massive avalanche cycle, with natural releases up to size 4 on all aspects and elevations. Heli bombing crews returned with stories of whole mountainsides ripping out to near ground just from the explosives landing on the slope, let alone going off after the fuse had burnt. FORECAST OF AVALANCHE DANGER UP TO MONDAY EVENING (March 17th) ALPINE - High TREELINE - High BELOW TREELINE ^Ö High, improving TRAVEL ADVISORY: The clues of avalanche danger will soon go away, leaving us with the feeling that things are now ok. They are not! Shallow angle slopes that have not avalanched during the storm will be under enormous strain from all this loading and will be ripe for human triggering. Big alpine glaciers with slopes of 31 to 35 degrees are likely candidates for this, as are open bowls of similar angle in the alpine and near treeline. SOUTH COLUMBIA REGION WEATHER: The freezing level managed to climb to 2000 m on Thursday, before falling to around 1200 on Friday. The weather improved Friday, with the cloud deck rising to near mountaintop and the sun actually poking through for a few minutes. The weather forecast predicts another system will come onshore and reach the region by Saturday, bringing more rain below 1800 m and snow above. SNOWPACK: About 100 cm of heavy, wet storm snow accumulated in the alpine, similar to adding 150 kg of weight to every square meter of snowpack surface. The upper 15 cm of snow is rain soaked below 1900 m elevation. The interface below the storm snow is still an easy shear, and the many crusts and buried instabilities in the mid and lower snowpack have been stressed to near or beyond the critical range by all the new loading. AVALANCHES: A second cycle of avalanche activity began Thursday afternoon, with natural releases to size 4 on all aspects and elevations. The frequency of avalanche activity will decrease on the weekend, but the potential for human triggering will still be huge. Any releases that are triggered are likely to be size 2.5 to 4.5. FORECAST OF AVALANCHE DANGER UP TO MONDAY EVENING (March 17th) ALPINE - High TREELINE - High BELOW TREELINE ^Ö High, improving TRAVEL ADVISORY: We^Òve been cooped up by despicable weather for a full week. The avalanche danger has improved, but not much. Shallow slopes in the 31 to 35 degree range may represent greater danger right now, as steeper slopes may have avalanched during the storm, but lower angled slopes that have not run will have been seriously overloaded and ripe for human triggering by even a single skier or sledder. KOOTENAY BOUNDARY REGION WEATHER: Temperatures peaked at plus 6 even in the alpine Thursday morning, with rain to mountaintop as a result. Winds remained moderate out of the SW. Up to 90 cm of snow fell before the moisture turned to rain. Conditions improved Friday, with the cloud deck rising to mountaintop and even a few minutes of sun being noted. The weather forecast predicts yet another low will arrive onshore this weekend, keeping temperatures mild and bringing more rain to low elevations, with snow above. Winds will increase as the system arrives. SNOWPACK: Storm snow amounts of 90 cm were reported by Friday, but the mild temperatures had promoted rapid settlement. In many areas this actually represented about 150 mm of water equivalent. This translates into 150 kg of weight being added to every square meter of snowpack surface, which is a huge load in anyone^Òs books. The interface just under the storm snow is a weak bond and was still easily triggered Friday. The series of crusts and buried surface hoar layers in the mid and lower snowpack are stressed to the point of failure by all the recent loading. AVALANCHES: A second widespread cycle of avalanches occurred Thursday afternoon, with naturals to size 4 being seen at all elevations and on all aspects. One report contained a description of a huge avalanche that failed deep, traveling 1200 meters before mowing down a stand of timber and traveling a further 200 m past the forest. The frequency of natural activity will decrease but the tendency for human triggering is still huge. FORECAST OF AVALANCHE DANGER UP TO MONDAY EVENING (March 17th) ALPINE - High TREELINE - High BELOW TREELINE ^Ö High, improving TRAVEL ADVISORY: Slopes in the 31 to 35 degree range, which may not have avalanched recently, represent a serious danger for human triggering since they are under a huge load now from the recent storm snow. Avoid alpine glaciers and any open alpine bowls with slopes near these angles. SOUTH ROCKIES REGION WEATHER: Huge winds, rapidly rising temperatures and snowfall rates in excess of 2 cm/hr finally hit the South Rockies as well on Thursday. Most stations reported 50 cm of storm snow falling on Thursday, bringing the total since Wednesday to near 75 cm. The freezing level climbed to 2300 m Thursday. Winds became moderate out of the SW except on the east slopes of the Rockies, where Chinook winds hit 100 km/hr. The forecast calls for some improvement Friday night, then more mild temperatures, wind and snow on the weekend. SNOWPACK: Below treeline the upper 25 cm of the snowpack is rain soaked, with some observers reporting the low elevation snowpack has become isothermal and weak. The interface under the storm snow is a failure layer still, and the mid snowpack strength has been very seriously eroded by heat. The lower snowpack is weak facets and depth hoar. AVALANCHES: Naturals to size 3 began to run frequently on Thursday, with some failures to ground being reported. FORECAST OF AVALANCHE DANGER UP TO MONDAY EVENING (March 17th) ALPINE ^Ö High TREELINE - High BELOW TREELINE - High TRAVEL ADVISORY: Failures to ground are nothing to mess with. Although conditions may improve later in the weekend, the potential for human triggering will not decrease by Sunday. Lower angled slopes may represent increased danger since higher angled slopes have more likely avalanched naturally. Even open timber or flat areas near avalanche paths may not be safe this weekend, since climax slides have been mowing down mature timber and running far out into valley bottom.