The Mt. Shasta Avalanche Center - US Forest Service  

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Update Wednesday 3/10/10 at 9am:  We've seen 6 inches of new in the past two days at the upper elevations- by far the lightest snow(6% water content) of the year.  Winds have been 35 - 56 mph in the past 8 hours at Grey Butte(8000').  Wind slabs have likely developed on S and E aspects.  Avoid new wind slabs as they will slide easily on the hard melt/freeze crust they are sitting on.  Be aware that NW winds can eddy around the south side of Mt. Shasta and this swirling can load many aspects so look for  clues (sastrugi, hollow sounds, shooting cracks).

Avalanche Advisory issued Sunday March 7, 2010 at 6:45 am  
By Eric White & Dan Towner                   

The Bottom Line:

Avalanche Danger Rating* for today:

Where:  Mostly LOW avalanche danger with pockets of MODERATE on steep N aspects below and near treeline, and on many aspects above tree line.   MODERATE means that natural avalanches are unlikely, but human triggered avalanches are possible.

Primary Concern:   wind slabs  above the treeline on most aspects, due to wind loading over the past several days with winds from a variety of directions
Secondary Concern:  isolated pockets of instability on steep slopes(greater than 35 degrees) at the base of last weeks new snow (1-3 ft.).

Size and Character:   medium wind slabs which will be hard and blocky

Sensitivity to Triggering:  Slabs becoming more stubborn, but could be triggered by an individual or machine, especially during the warmer parts of the day.

Confidence in today's Forecast:  High.  We feel pretty good with the snow information and weather forecast.

The Details:

This Season:  Strong El Nino conditions have existed in the equatorial Pacific over the last 3 months.  Climatologists predict equal chances for precipitation over the next 3 months and above normal temperatures.  Since September 1, our precipitation is 126% of normal in Mt. Shasta City (NWS ASOS station).  The Martin Luther King Jr. storm was the biggest of the season with several days setting precipitation records.  From January 17 to January 26, we received 12.80 inches of water and 9-10 ft. of snow at mid elevations.  Ice and very wet snow during this storm caused a plethora of snapping trees and power lines in town, closing roads and brought a state of emergency to Mt. Shasta City.  Since 1948, this was the 3rd wettest January on record.  Snow survey results at the beginning of February in the Mt. Shasta area show the snow pack at 143% of normal.  

Weather Observations at 5 am:  We have mostly clear skies this morning and calm winds in town.  It is currently 31F in Mt. Shasta City and the barometric pressure is decreasing slightly. 
On Mt. Shasta:  In the Old Ski Bowl (7,600') on the S side of Mt. Shasta, we have received no new snow in the last 24 hours, with 3 inches of settlement.  We are measuring 155 inches of snow on the ground.  Temperatures have been between 26F yesterday morning to 34F yesterday afternoon and it is currently 26F.  At Grey Butte (8,000') on the S side of Mt. Shasta winds averaged 15 mph out of the ENE,  with gusts to 42 mph from the NE in the past 24 hours.  Winds have slowed to 4-7mph out of the SE early this morning.  
Castle/Mt. Eddy:   Castle Lake received no new snow in the last 24 hours, with 2 inches of settlement, and we have147 inches of snow on the ground.  Temperatures were between 31-43F over the last 24 hours and it is currently 31F.  On Mt Eddy, we received no new snow and 3 inches of settlement with 119 inches on the ground.  Temperatures were between 27-31F and it is currently 27F.  

Weather Forecast:  Today looks like it will be a nice day, with plenty of sunshine and a few clouds.  A storm will arrive tonight bringing cold air and this coming week will cool down to normal or below normal temperatures.  The storms this week, however, will not be travelling in a favorable direction for Mt. Shasta, so it doesn't look like we will see that much snow.  Look for increasing clouds tonight before the first wave.  Today:  Sunshine with some clouds and temperatures below tree line warming into the mid to upper 40's.  Winds below tree line will be light from the NE, moving to the W and SW later today and tonight.  Near and above tree line, temperatures will warm into the 30's, reaching the upper 30's near tree line and winds will be light from the NE and E this morning, then move to the WSW later today and tonight and increase to 15-25 mph.  Next 4 days:  Cooling temperatures Monday with light snow fall possible  and increasing SW winds.  Tuesday will be a break with another storm arriving Tuesday night into Wednesday with light snowfall on Mt. Shasta and increasing NW winds becoming strong on the upper mountain.  Thursday will be another break with warming temperatures.

Snow Pack:   Tuesday and Wednesday brought close to 2 feet of new snow and great conditions.  We have had 10-13 inches of settlement since then.  Strong E winds loaded W aspects above the treeline yesterday and last night. Northerly aspects were previously loaded during the last week.  However, due to the variability of  winds on the upper Mountain, wind slabs may have developed on a  variety of aspects above the treeline and these windslabs will retain some sensitivity today.  Supportable crusts have developed on most southerly aspects, especially open areas near and below the tree line, creating a corn-like snow surface during the warmer parts of the day.  Some protected northerly aspects could still hold powder from Tues/Wednesdays storm- be aware of possible isolated areas of instability on these aspects.  Check the snow stability before you decide to drop in as areas of instability can still be found - especially on slopes greater than 35 degrees and on northerly aspects.  We saw a few natural avalanches which occurred on Tuesday night or Wednesday during the storm.  These were on W and NW aspects near tree line with one on Criblet ridge between Powder and Sun Bowls being 2000 ft. wide with a 1-2 ft. crown.  We did a crown profile and found that the new snow slide on a layer of graupel on top of a melt/freeze crust (see photo and video link below).

Natural avalanche on 3/2/10 on Crible ridge between Powder and Sun bowls, Mt. Shasta.  W aspect 7900-8400 ft., 35-40 degree slope.  Crown fracture 1-2 ft. thick and 2000 ft. wide.  Photo taken on 3/6, MSAC.
 

Link to video showing criblet ridge after avalanche 3/2/10

Link to video showing Rutschblock stability test 2/27/10

Link to video showing Extended Column Test 2/27/10

Link to video showing Rutschblock stability test 2/5/10

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:  Groomed Pilgrim Creek to Deer Mnt. on 3/4 with some on the Whaleback.   The snowcat is broken down right now...

Go to "Photos/Avy Shots" for photos of recent avalanches.  

Please report weather and snow observations- you could help save a life:  (530)926-9614  Thanks!