The U.S. Forest Service Shield The Mt. Shasta Avalanche Center Avalanche Advisory for Wednesday, December 19, 2007 at 4:00pm By Eric White The Bottom Line: Avalanche Danger Rating for today: Trend: Extreme Widespread natural or human triggered avalanches are certain High Natural and human triggered avalanches are likely. ] Considerable Natural avalanches are possible and human triggered avalanches are probable. Moderate Natural avalanches are unlikely. Human triggered avalanches are possible. Low Natural avalanches are very unlikely. Human triggered avalanches are unlikely. & Avalanche Danger is expected to Increase " Avalanche Danger is expected to continue at this rating ( Avalanche Danger is expected to Decrease Where? Above 6000 ft on Easterly and Northerly aspects greater than 35 degrees on Mt. Shasta. Above 5500 feet on northerly aspects in the Castle/Eddy area. Size and Character: Medium sized slabs below tree line and medium hard slabs (wind slabs) which will travel to tree line. Sensitivity to Triggering: These will be triggered by an individual or group. Level of Uncertainty in forecast: Low Moderate High The next Avalanche Advisory will be posted: 12/20/07 --- The Details: This Season: We had a few early season hints of snow, then a dry spell with December starting to show signs of winter. Our precipitation is around 90% of normal and we may catch up over the next few days. We currently have around 2-3 feet of new snow on a thin and week old snow surface. We are in a "La Nina" climate condition which often means wetter than normal winters in our area. Weather Observations: We currently have limited remote weather station data. Mt. Shasta - We currently have 38 inches of snow on the ground near tree line with around 4-6 inches of new snow over the last 24 hours. The snow settled 4 inches overnight. In the last 24 hours temperatures have ranged between 23F to 31F at 7000 ft. We have a storm total of 28 inches of new snow and around 3.74 inches of water content. Winds this morning above tree line were estimated at around 45 mph from the W/SW, and around 25 mph below tree line from the S/SW. Castle/Mt. Eddy - Mt. Eddy received around 6 inches of new snow in the last 24 hours with 4 inches of settlement. Temperatures were between 24F to 29F over the last 24 hours. We estimate around 2 feet of snow on the ground. Weather Forecast: The current storm came in a little late but has been dumping most of the day and will continue with earnest tonight. By tomorrow mid morning the front will pass through and turn to light snow showers with the temperatures and the snow level dropping well below town. We may see 10 inches of new snow by tomorrow afternoon above 5000 ft. Temperatures at tree line will drop into the teens tomorrow. Winds above tree line will increase tonight from the W/SW to 35-65mph, slow tomorrow morning and then increase from the NW to 70 mph on the upper mountain as a brief period of high pressure develops. Wet weather is expected through the next week with breaks between storms. Snow Pack: We had some natural avalanches yesterday and several reports of classic signs of instability - shooting cracks and "whumpfing" sounds. Although this current storm came in warm and is cooling, the snowfall intensity tonight, coupled with the forecast winds, will create instability on leeward slopes, especially above tree line. Use caution on Northerly and Easterly aspects greater than 35 degrees where wind loading is occurring. Many people are excited for the beginning of winter recreation, but, don't let that blind you to the sensitive conditions which exist. Continue to watch for shallowly buried rocks, sticks and logs and snow collapsing near trees and brush. Some important thoughts: This advisory does not apply to Ski Areas or Highways and is for the Mt. Shasta, Castle Lake and Mt. Eddy back country. Use this information for guidance only. You may find different conditions in the backcountry and should travel accordingly. This advisory expires at midnight tonight. As always, use safe travel practices: travel with a partner, travel one at a time in suspect areas, go from one island of safety to another, choose safe routes, wear a transceiver, carry a shovel and probe, and know how to use your gear! Please give us comments on our new format and report weather and snow observations: (530)926-9614 Thanks! Some things to consider: Backcountry travelers should make terrain, weather and snow pack evaluations as they travel over snow covered terrain. Remember that seemingly insignificant slides may be dangerous. Almost half of all avalanche fatalities occur in slides traveling less than 300 feet. Early Season Watch Outs! * Surface sluffs and wind slabs * Shallowly buried rocks and trees can cause serious damage or injury. * Sink holes around brush and small trees can be dangerous. * Snow bridges over crevasses can be touchy and unsupportable. * Shallow snowpack with cold air temperatures can produce unstable snow These are just a few things you should watch out for when traveling during the early part of the winter season. The Five Red Flags of Avalanche Danger any time of year include: 1) Recent/current avalanche activity 2) Whumpfing sounds or shooting cracks 3) Recent/current heavy snowfall 4) Strong winds transporting snow 5) Rapid warming or rain on snow.