Advisories Archived Advisories
| MSAC Avalanche Advisory (Archived-01-17-10 10:25:58) |
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Avalanche Advisory issued Sunday January 17, 2010 at 7:15 am By Eric White & Dan Towner The Bottom Line:Avalanche Danger Rating* for today:
*Most avalanche accidents occur during Moderate or Considerable avalanche danger.
Where: MODERATE avalanche danger this morning, increasing to CONSIDERABLE by tonight, especially near and above tree line on N and E aspects Primary Concern: wind slabs near and above tree line, especially on N and E aspects Secondary Concern: storm slabs from heavy snow fall late today Size and Character: medium sized wind slabs (blocky); medium sized soft slabs in storm snow Sensitivity to Triggering: slabs will be easy to trigger near and above tree line later today; soft slabs will be easy to trigger by tomorrow morning on slopes greater than 35 degrees Confidence in today's Forecast: Moderate. Some discrepancies on total amount of snow
Trend over next 4 days: With a series of storms coming in this week and several feet of snow possible, the avalanche danger will increase to CONSIDERABLE and probably stay there most of the week. Wind directions and amount and rate of snow fall will be important weather factors to watch.
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 78% 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 light rain/mist in town this morning with light S winds. It is currently 38F in Mt. Shasta City and the barometer continues to drop. On Mt. Shasta: In the Old Ski Bowl, we are measuring 62 inches of snow on the ground at 7600 ft. with a trace of new snow and 1 inch of settlement over the last 24 hours. Temperatures were between 23F last night to 33F yesterday at noon and it is currently 27F. Winds on the S side of Mt. Shasta at 8000 ft. (Grey Butte) have averaged 9 mph over the last 24 hours and were from the S. Winds over the last 12 hours were 10 mph from the SSE and gusted to 28 mph from the S. At 6 am winds are 13-21 mph from the SSE and it is 26F. Castle/Mt. Eddy: On Mt. Eddy we are currently measuring 42 inches of snow on the ground at 6800 ft. with a trace of new snow and little settlement over the last 24 hours. Temperatures were between 27-33F and it is currently 29F. At Castle Lake we are measuring 34 inches of snow on the ground with a trace to 1 inch of new snow and little settlement over the last 24 hours. Temperatures over the last 24 hours were between 29-37F and it is currently 30F. Upper air measurements this morning show temperatures a few degrees warmer than yesterday. Weather Forecast: The first storm turned out to be a little weaker than forecast as it was pushed slightly north. However, it still looks good for today with the next storm arriving late morning and peaking this evening. The snow level will start near 5500 ft. and drop to 4500 ft later today and then get close to town tonight and tomorrow morning. At mid elevations on the mountain we could see as much as 12-17 inches of snow by tomorrow morning. Today: A winter storm warning has been posted for Mt. Shasta for the next 36 hours. Expect increasing snow fall today. Below tree line we will see temperatures warming to the low to mid 30's with winds from the SE and S at 10-15 mph. Near and above tree line temperatures will be in the 20's with winds SSW increasing to 30-40 mph with gusts around 50 mph. Extended: While timing and amounts of precipitation are hard to forecast now, we will have wet weather all week with snow levels near town. Storms will focus in the central and southern part of the State this week, but still bring snow our way. The strongest winds look to be on Monday and from the south. Snow Pack: The best conditions today will be later in the day as the snow begins to accumulate. However, along with the powder, the avalanche danger will start to increase. Wind loaded areas on N and E aspects will become sensitive by this afternoon and evening. Near and above tree line, the new snow load by tomorrow morning may be enough to stress weak layers in the older snow in similar places where we saw failures this week during stability tests and in natural avalanches. So... Be observant to snow conditions, watching for and avoiding wind loaded areas and remember that the greatest sensitivity to triggering slides will probably be during the heaviest snow fall and strongest winds. Cornices will be very sensitive this week and should be avoided as they will trigger wind slabs below them if they break. Remember also the 5 Red Flags of avalanche danger: recent or current avalanches, heavy snow fall, wind transporting snow, "whumpfing" sounds or shooting cracks, rain or rapid warming. Don't let your urge for powder blind you to the clues nature provides of unstable snow conditions! Link to video showing Rutschblock stability test 1/14/10 Link to video showing stability test 1/9/10 Link to video showing the 1/2/10 Pelican Butte avalanche accident (recovered alive) 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: (Avalanche Transceiver) 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. No dinner, but snacks and deserts will be available. Yogoman Burning Band will get you dancing! Tickets available at The Fifth Season and Shasta Base Camp. 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. 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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