San Juan North ============== Current Keywords: CONSIDERABLE, MODERATE, avalanche danger, crusts, drifted, drifting, drifts, faceted, facets, high pressure, naturals, paths, slab, slabs, starting zones, trough, weak layers, wind-loaded, windslabs, Mountain Weather and Avalanche Forecast for the Northern San Juan Mountain Zone Forecast Issued on 1/1/2008 4:20:52 PM Forecaster: Spencer Logan Weather Synopsis High pressure is building, bringing relief / from Boreas's fury, temper, and strength. / He sent two thousand seven out in style, / Backing up traffic many hours and miles. / One final, parting kiss to say good bye, / As around midnight the jet stream dipped down / to blast the peaks, gusts to sixty four / on Monarch, but down from the day before. / By dawn the jet has moved off to the east. / Zephyrus comes, airmass stable and dry, / West and northwest winds, at moderate speeds. / The temperatures will rise, slowly at first, / Warming on Wednesday and into the week. / Some clouds to the south slide under the ridge, / Which breaks down Friday as a trough plows east. Two thousand eight arrives sunny and mild, / With precarious snow on a holiday, / A combo that should give everyone pause, / Poetry, jokes, celebration aside. / Make yourself a New Year's resolution: / Know obvious clues to unstable snow, / Select terrain condition appropriate, / Travel smart once you're in the dragon's den / From island to island one at a time, / Carry the right gear and know how it works. / Combine these with some healthy common sense, / You can have a great backcountry New Year. Weather Tuesday Night Wednesday Wednesday Night Temperature(°F) 0-5 22-27 10-15 Wind Speed(mph) 10-20 10-20 10-20 Wind Direction Var SSW SSW Sky Cover Partly Cloudy Partly Cloudy Mostly Cloudy Snow(in) 0 0 0 Snowpack Discussion Observers reported avalanches on most aspects from Sunday, Monday, and Tuesday. West, north, northeast, southeast, and south aspects all had activity. Sunday near Lake City a skier triggered an avalanche on a northeast slope just above treeline - the skier was not injured. Southerly aspects were particular active, with many naturals running from the combination of loading from "north winds and south crusts" underneath the slabs. Most of the activity was confined to the recent snow, only a foot or two deep. There was one exception, a 4 foot deep and 1000 foot wide monster that ran to the ground on a northeast aspect. It's a reminder that the snowpack still has weak facets at the bottom--stubborn and capped with a solid slab but ugly if they fail. There were ferocious northwest winds over the weekend. Windspeeds eased a bit on Monday as they swung to the north, back to the speeds perfect for drifting snow into avalanche starting zones. So, snow was stripped off slopes above treeline and deposited low into tracks or below treeline. Then what little snow was left was drifted higher into the paths. Observers near Telluride found new drifts more than 6 feet deep, next to areas scoured back to tundra and dirt. Remember that wind not only redistributes large amounts of snow, it also breaks down snow grains and packs them together tightly, forming cohesive windslabs that have the potential to fracture above the point of initiation and propagate over long distances. The snowpack faceted away under the cold temperatures last week, causing layers of snow grains to become angular and cohesionless. These weak layers, however thin, will not bond well with the windslabs above them. On northerly terrain, deep slab instabilities are a concern as weak snow at the base of the snowpack persists. On the sunnier aspects, the upper windslabs formed on top of various layers of crusts sandwiched around faceted snow. The snowpack is returning to the familiar San Juan stack of windslabs on facets. Scale back your expectations from earlier this season accordingly. Wednesday will be the first warm, sunny day in a long time. Expect some loose activity on steep slopes as the snow surface heats up. Avalanche Danger The avalanche danger for the Northern San Juan zone is CONSIDERABLE on all aspects near and above treeline. Below treeline the danger is MODERATE on all aspects. Be particularly careful on steep, convex, wind-loaded slopes near and above treeline.