Advisories Archived Advisories
| MSAC Avalanche Advisory (Archived-01-01-10 11:12:34) |
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Avalanche Advisory issued Friday January 1, 2010 at 8:00 am By Eric White HAPPY NEW YEAR! The Bottom Line:Avalanche Danger Rating* for today:
*Most avalanche accidents occur during Moderate or Considerable avalanche danger.
Where: CONSIDERABLE on wind loaded slopes near and above tree line; MODERATE elsewhere. Primary Concern: wind slabs on N/NE/E/SE aspects, near and above tree line Secondary Concern: Storm slabs 1 ft. thick near and below tree line on slopes greater than 35 degrees; Deep slab instability, especially where the ground surface is smooth on slopes greater than 35 degrees where facets and depth hoar occur on the ground, mostly on northerly aspects; wet slabs at low elevations on all aspects greater than 30 degrees triggered by rainfall. Size and Character: medium wind slabs (hard/blocky);small to medium storm slabs (soft); small to medium deep slabs(mixed); small to medium wet slabs during rainfall (wet and heavy) Sensitivity to Triggering: wind slabs will be sensitive! and easily triggered by an individual or group; storm slabs will be sensitive on steep slopes and could be triggered by an individual or group; moderate to strong force required to trigger deeper slabs Level of Uncertainty in today's Forecast: Low. Good confidence with snow conditions and weather forecast.
The Details:This Season: Moderate El Nino conditions exist in the equatorial Pacific. Climatologists predict a 33% chance of above normal precipitation for much of northern California over the next 3 months, and higher chances of above normal precipitation in central and southern California. Since September 1, our precipitation is 75% of normal in Mt. Shasta City (NWS ASOS station). Our biggest storm so far this season began on Columbus Day and the thin early season snowpack was subjected to very cold temperatures in early December creating a weak layer on the ground. Weather Observations at 5 am: We have light rain in town, with light SE winds. It is currently 37F in Mt. Shasta City and the barometer decreasing. On Mt. Shasta: In the Old Ski Bowl, we are measuring 46 inches of snow on the ground at 7600 ft. with 8 inches of new snow and 1 inch of settlement over the last 24 hours. Temperatures were between 20F yesterday morning to 26F this morning and the current temperature is 26F. Winds on the S side of Mt. Shasta at 8000 ft. (Grey Butte) have averaged 17 mph from the SW during the last 24 hours with gusts to 42 mph from the SW this morning. Currently (6 am) winds are 20-35 mph from the SW and it is 25F. Castle/Mt. Eddy: On Mt. Eddy we are currently measuring 39 inches of snow on the ground at 6800 ft. with 8 inches of new snow little settlement over the last 24 hours. Temperatures were between 25-30F and it is currently 30F. At Castle Lake we are measuring 37 inches of snow on the ground with 8 inches of new snow and little settlement over the last 24 hours. Temperatures over the last 24 hours were between 25-30F and it is currently 30F. Upper air measurements this morning show temperatures 5-10 degrees cooler than yesterday morning. Weather Forecast: The last part of this warm storm will be moving through during the first part of New Years' Day, turning to showers later today. As the storm moves easterly it will begin hitting the Tahoe area. We will have a break this weekend and unsettled weather going into the week. For today we will see snow above 5500 ft. with 4-6 inches possible at mid elevations by tomorrow morning. Temperatures near tree line will hover in the upper 20's, while at lower elevations they will warm to the low to mid 30's. Winds will continue to be strong above tree line at 40-60 mph from the SW and W. On the upper mountain, winds will be 55-80 mph from the W. Winds will move to the NW late tonight and into Saturday, and maintain moderate to strong speeds. Snow Pack: People were enjoying powder conditions yesterday below tree line where winds were light and visibility was better. Looks like more powder today with the best conditions in the trees at 6000 to 8000 ft. During stability tests yesterday at 8300 ft. on a low angle (24 degree) S aspect, all failures were occuring easily in the new snow (6-8 inches below the surface), but not propagating (ECTN 3-8). On the Rutschblock test, it failed on the same layer (6-8 inches down) under moderate force (R5, Q2). I continued to find weak layers (facets) deep in the snow pack, but I did not observe any failures in those layers under my weight. Relatively shallow snow pack continues, with only 3-4 ft. of snow and some obstacles (rocks, logs, staubs) poking through. My concerns today are with wind slabs near and above tree line on N and E aspects as winds have been steady over the last 24 hours. Wet slabs will be possible at lower elevations (5-6000 ft.) due to rain/wet snow. Where most people will be enjoying powder in the backcountry today (7-8000 ft.) my concern is with storm slabs around 1 ft. thick on steep slopes (greater than 35 degrees). SO... make a New Years' resolution and learn more about avalanches or practice more with your transceiver and today, think about staying on slopes less than 30 degrees, away from wind loaded areas.
Large facets found in thick layer near ground. Mt. Shasta, December 26, 2009, 7400 ft., NW aspect. This weak layer has been persisting for 3 weeks and continued temperature gradients with thin snowpack will help this to remain a concern on steep slopes with sparse to no anchors. Look for large (2-4 mm) angular grains. The total width of this photo is 13.5 mm. Link to short video showing shallow snowpack and facet layer on ground, 12/24/09. 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! Pilgrim Creek Snowmobile Park: Not enough snow for grooming yet.
MSAC Upcoming Events: Avalanche Awareness: Friday night, January 15, 6 pm at the Mt. Shasta Library, 515 E. Alma St. A National Weather Service Meteorologist and Climatologist will briefly discuss the climate forecast for our area at the start of the talk. Don't miss this opportunity! Avalanche Transceiver Clinic: Saturday, January 16, 9 am at The Fifth Season, 300 N. Mt. Shasta Blvd. We will do this with or without snow and dress to be outside regardless of weather. 8th Annual SNOWBALL: Saturday, January 23 begining at 6 pm and held at the Weed Sons of Italy hall. This fundraising event by the Friends of the Mt. Shasta Avalanche Center is always a blast with tons of raffle items, music, dancing and a variety of beverages. See you there! Go to "Photos/Avy Shots" for photos of recent avalanches. Go to "Forums", "Snow pack Videos" to see past snow pack videos. Please report weather and snow observations: (530)926-9614 Thanks! 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.
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