Aspen ===== Current Keywords: CONSIDERABLE, HIGH, avalanche danger, crusts, depth hoar, drifts, faceted, facets, human triggered, natural avalanche, stress, surface hoar, weak layers, wind slabs Issued 12/13/2008 2:56 PM by Scott Toepfer Avalanche Watch in Effect through 12/14/2008 12:00 PM Weather Discussion Storm systems are going to race across the state until maybe next weekend. Here's the shorter term look. Currently a 90 to 100 knot jet has nosed over the San Juans where it has been fairly windy today. A bit of a dry slot moved over during the Saturday morning hours, but satellite images show things filling in nicely. Near sunset Saturday we are looking at blizzard conditions favoring the San Juan, West Elks & Elks, Vail Pass to Beaver Creek area (not quite as much for Summit County), plus the Steamboat and Grand Mesa zones. Onset of snowfall looks to be very rapid and powerful from around 4-7 tonight in favored areas. The jet stream will shift from a westerly flow to a stronger southwest flow, in the 150 knot range for Saturday night. Very strong winds are anticipated Saturday night across the state. With the progressive nature of the pattern look for some drying to begin in the San Juan mid-day Sunday, and this spreading north by mid-to-late-afternoon across the central and northern zones. It's going to get cold too. Look for high temperatures Sunday to come early in the morning. The jet sags a little ways into NM Sunday and this will help us see an easing in windspeeds, at least temporarily. Next system is progged to move in Monday evening & exit Tuesday mid-day. Another on Wednesday, & another for next weekend. If the first blow doesn't hit us hard enough, look for several more hard hitting systems to stress our tender snowpack. Weather Forecast Fields Saturday Night Sunday Sunday Night Temperature (°F) 10-15 5 to 10 -11 to -6 Wind Speed (mph) 17-27 G50s 12-22 G30s 5-15 G20s Wind Direction WSW WSW W Sky Cover Overcast OV Overcast OV Mostly Clear CM Snow (in) 15-20 4-7 0 Snowpack Discussion More snowfall and increasing winds will continue to increase the avalanche danger into the coming week. If you are heading out into the backcountry over the next several days, expect to find fresh drifts and wind slabs on slopes facing N-NE-E and even around to the south, all elevations. The anticipated strong SW winds will continue to transport snow into Sunday morning. Shadier aspects already have a very weak and tender snowpack. The additional load of new wind slabs will increase the odds of natural avalanche activity. Human triggered slides will be probable to likely on all aspects for awhile. The current snowpack also lends itself to triggering large avalanches from well down slope. New snow that fell in the last 24 hours has buried a few weak layers that existed in the upper snowpack. There you will find layers of surface hoar, crusts, and a few faceted snow grains. Also a concern will be the facets and depth hoar at the base of the snowpack that formed from a dry period in our November weather. You will need to pay attention to all these layers as you travel in the backcountry today. All steeper slopes should be treated with caution, or avoided if you don't have the skills to evaluate the snowpack on them. Whumphing and some cracking in the snowpack will be good clues to the presence of these weak layers buried below. That weak layer at the base of the snowpack will be very problematic as snow pile up this weekend. Avalanche Danger Avalanche danger for the Aspen zone is forecast to jump to HIGH on slopes facing N-NE-E-SE near and above treeline. New snow and some stronger SW winds will continue to stress an already tender snowpack on these slopes. On other aspects and elevations the danger bumps to CONSIDERABLE.