| The Mt. Shasta Avalanche Center - US Forest Service Due to staffing cuts, Advisories will only be posted on Friday, Saturday & Sunday from December to April Avalanche Advisory for Sunday, January 4, 2009 at 6:45 am By Eric White The Bottom Line: Avalanche Danger Rating* for today: | | EXTREME | Avoid all avalanche terrain. Travel only on gentle slopes well away from avalanche paths and run-out areas. | | | High | Widespread dangerous conditions. Exposure to avalanche terrain is not recommended. Extensive experience assessing snow and terrain is required for safe travel. | | | Considerable | Variable conditions and uncertainty require conservative decision making. Careful route selection and good travel habits are required. | | X | Moderate | locally unsafe conditions. Evaluate the snow and terrain carefully. Use good travel habits to minimize risk. | | | Low | Generally safe conditions. Watch for unstable snow on isolated terrain features. |
*Most avalanche accidents occur during Moderate or Considerable avalanche danger. 24 hour trend | ⇒ | Avalanche danger is expected to increase. | |
| Avalanche danger is expected to continue at this rating | |
| Avalanche danger is expected to decrease. | Where: Above tree line: MODERATE avalanche danger, especially on E, SE and S aspects Below tree line: Low avalanche danger in most areas with pockets of Moderate avalanche danger on E, SE and S aspects Primary Concern: Wind slabs near and above tree line on E and S aspects Secondary Concern: Wind slabs below tree line on E and S aspects Size and Character: Medium wind slabs above tree line; small and shallow wind slabs below tree line Sensitivity to Triggering: Becoming more stubborn; an individual, group or machine could trigger in specific areas
Level of Uncertainty in today's Forecast:
| The next Avalanche Advisory will be posted: Friday, 01/09/09 |
The Details: This Season: Following a very dry summer, we had significant snowfall above tree line in early November with 5-7 feet. Warm and dry weather followed, creating a smooth and firm melt/freeze snow pack 2-3 feet deep above 8500 ft. in elevation. Unusually cold weather in the second week of December created weak layers. A warm front at the end of December created a rain crust. Shallow and below normal snow pack continues with around 2-3 feet in most areas. Precipitation so far this season is 70% of normal. The forecast is now official for La Nina conditions to continue which is good for most of the Pacific NW, but can leave us with windy and drier conditions similar to last season. Weather Observations: We have mostly clear skies and light N winds in town this morning. It is currently 13F in Mt. Shasta City and a chilly 3F over in McCloud Valley. Mt. Shasta: We are measuring 25 inches of snow on the ground at 6700 ft. with no new snow over the last 24 hours and 1 inch of settlement in the snow pack. Temperatures cooled, ranging between 4F yesterday morning to 23F yesterday afternoon at 6700 ft. and it is currently 5F. Winds this morning are light and variable with gusts to 20 mph from the SE below tree line. At 10,000 ft. winds are very light from the N. On the upper mountain winds are estimated at 35 mph from the NW this morning. Castle/Mt. Eddy: Mt. Eddy received no new snow and little settlement in the last 24 hours with 20 inches of snow measured on the ground at 7200 ft. The temperature on Mt. Eddy this morning is 21F. Near Castle Lake we are measuring 20 inches of snow on the ground with no new snow over the last 24 hours and little settlement. Temperatures near Castle Lake have been between 2-28F over the last 24 hours and currently it is 7F. While a temperature inversion has created cold temperatures in valleys and basins, upper air measurements this morning show temperatures 5 degrees warmer than yesterday morning. Weather Forecast: A warm front is now hitting Washington where its' focus will remain over the next few days. A strong high pressure has formed in the eastern Pacific off of the California coast and will remain there through the week. A few storms will drop in behind the high pressure and bring light precipitation to our area. For today we will see increasing high clouds, becoming overcast in the afternoon. Precipitation will begin tonight with the snow level starting near town (3500 ft.) and creeping up as the warm air slowly moves in. By Monday morning the snow level could climb to 6500+ ft. It looks like we could receive 1-2 inches by early tomorrow morning and another 1-3 inches on Monday above 7000 ft. Slight changes in this storm could alter this easily, keeping some uncertainty in the 72 hour forecast. Today, temperatures will warm to the upper 20's to low 30's below tree line and into the mid 20's above tree line. Winds will remain light this morning, increasing to 10-20 mph from the SSW below tree line. Above tree line winds will be light this morning and increase in the afternoon to 20 mph from the WNW. By Monday morning, winds above tree line will increase to 45-50 mph from the NW. Snow Pack: Finally we have a crust between us and the ground, lessening the threats from logs, rocks, brush, etc... Good conditions continued yesterday below tree line with a few inches of fluff on a concrete crust. We still have concerns for small wind slabs below tree line on easterly aspects and larger ones above tree line. For those traveling above 9000 ft., larger wind slabs formed Thursday and Friday (1/1-2/09) on E, SE and S aspects and may become a little easier to trigger with warming temperatures today. When you hear hollow sounds in the snow pack, you are on a wind slab and should delicately move to lower risk areas. I observed some large surface hoar crystals on the snow surface below tree line yesterday. This classic weak layer, along with the low density powder in the top few inches of the snow pack, and, all of this sitting on a very firm crust, will form good conditions for avalanches if we receive a few inches of warmer and heavier snow which is forecast for tonight and Monday. While we are not expecting very much snow out of this storm, it will be and "upside down storm", as temperatures increase over the next 36 hours. This will create some small and shallow instability in the snow at the beginning of the week. Wind loading will add to this. So, continue to be observant for changes in weather and the snow pack as we go into the week. 
Large surface hoar crystals formed 12/16-18 in many areas below treeline. photo 12/17/08, Castle Lake 
Large surface hoar crystals formed 12/29-31/08 at Castle Lake, growing on a rain crust.  
2-6 mm surface hoar crystals formed again below tree line on 1/2-4/09 sitting on a 3 inch layer of powder over a concrete crust. 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 back country 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 report weather and snow observations: (530)926-9614 Thanks! Pilgrim Creek Snowmobile Park: No grooming has taken place this season due to thin snow pack.
Upcoming Events:
Avalanche Awareness Presentation, Friday, January 16, 6pm: This is a great FREE intro to avalanches or a great refresher to those who have taken classes before. In this 1 hour talk, we will discuss the factors which lead to avalanche formation and some of the observations and skills you can use to identify instability in the snow pack. Join us at the Mt. Shasta City Library, 515 East Alma St., Mt. Shasta, next to Sisson Middle School.
Avalanche Transceiver Clinic, Saturday, January 17, 9am: Bring your transceiver or use a demo to practice your rescue skills. Dress warm and meet us at The Fifth Season, 303 N. Mt. Shasta Blvd., at 9 am. FREE! Avalanche Awareness, Wednesday, January 21, 7pm, Turtle Bay Exploration Park: Join us for this 1 hour presentation on avalanches and traveling safely in the back country during winter and spring.  7th Annual SnowBall, Saturday, January 24, 6pm - ? This great event is the major fund raising project of the volunteer, non-profit, Friends of the Mt. Shasta Avalanche Center who support our work. Dinner, music, dancing, beer, wine, soda and tons of raffle/silent auction items. See you there!
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.
Please report weather and snow observations: (530)926-9614 Thanks!
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Advisories 
