Advisories Archived Advisories
| MSAC Avalanche Advisory (Archived-01-09-10 09:20:00) |
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Avalanche Advisory issued Saturday January 9, 2010 at 7:00 am NOTE: Lost skier was found yesterday morning and was OK. Thanks again to all the locals who helped in the search: Danni, Ty, Robin, Doug, Shanon, Chris. By Eric White The Bottom Line:Avalanche Danger Rating* for today:
*Most avalanche accidents occur during Moderate or Considerable avalanche danger.
Where: MODERATE avalanche danger on slopes greater than 35 degrees above tree line; LOW elsewhere Primary Concern: wind slabs above tree line Secondary Concern: Deep slab instability due to several weak layers lower in the snow pack Size and Character: small wind slabs (blocky); small to medium sized deep slabs Sensitivity to Triggering: wind slabs will be easy to trigger by an individual; deep slabs will be hard to trigger Level of Uncertainty in today's Forecast: Moderate. While we were in the snow during the search yesterday, we were unable to do a full snow pack analysis.
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 68% 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 snow pack was subjected to very cold temperatures in early December creating a weak layer on the ground. Weather Observations at 5 am: We have partly cloudy skies in town and calm winds. It is currently 37F in Mt. Shasta City and the barometer has increased slightly. On Mt. Shasta: In the Old Ski Bowl, we are measuring 44 inches of snow on the ground at 7600 ft. with 1 inch new snow and 1 inch of settlement over the last 24 hours. Our instruments measured 0.31 inches of water over the last 24 hours. Temperatures were between 27F to 38F and it is currently 32F. Winds on the S side of Mt. Shasta at 8000 ft. (Grey Butte) have averaged 10 mph from WSW during the last 24 hours with gusts to 28 mph from the WSW. Castle/Mt. Eddy: On Mt. Eddy we are currently measuring 29 inches of snow on the ground at 6800 ft. with no new snow and 1 inch of settlement over the last 24 hours. Temperatures were between 33-41F. At Castle Lake we are measuring 27 inches of snow on the ground with no new snow and 3 inches of settlement over the last 24 hours. Temperatures over the last 24 hours were between 34-43F and it is currently 34F. Upper air measurements this morning show temperatures a few degrees cooler than yesterday. Weather Forecast: Today's weather will be similar to the past several: clouds and a slight chance of light precipitation with the snow level 6500-7000 ft. and possibly higher, but only a few snowflakes and little accumulation is expected. Temperatures today below tree line will warm to the upper 30's to low 40's, while above tree line temperatures will warm to the low to mid 30's. Winds below tree line will continue to be light and variable, but most likely from the SSE. Near and above tree line winds are expected to be 10-15 mph from the SW. Looking ahead, it looks like a storm will arrive early in the week with winds increasing on Monday and precipitation on Monday night and Tuesday with snow levels near 5500 ft. Snow Pack: With warm temperatures and small amounts of rain and mist, the snow pack has settled dramatically. At low elevations (6000 ft. and lower) the snow is pretty sloppy. At upper elevations, light snow fall and light to moderate winds have created some small wind slabs, mostly on N and E aspects. Near tree line, temperatures finally cooled this morning and the snow will be firm with around 6 inches of a wet melt/freeze crust. In boots, we were post-holing calf deep yesterday. This will soften slightly today as temperatures warm. While the snow pack stability has increased, our main concern is for small wind slabs at mid and upper elevations.
The pesky rain crust we received from a freezing rain event on New Years' Day (left photo). The right photo shows the slab released on stability tests 1/2/10 with moderate force . Link to video showing the 1/2/10 Pelican Butte avalanche accident (recovered alive) Thanks Jim B! Link to short video #1 from 1/2/10 showing wind loading Mt. Shasta Link to short video #2 from 1/2/10 with Rutschblock test results, Mt. Shasta Link to short video showing shallow snow pack 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! No reservations required - just show up! 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. No reservations required - just show up! 8th Annual SNOWBALL: Saturday, January 23 beginning at 7 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. This will be a joint event, working together with the Mt. Shasta Nordic Center. 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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