The Mt. Shasta Avalanche Center - US Forest Service  

Transceiver Clinic today, meet at The Fifth Season 9 am, then to Bunny Flat - Free

Avalanche Advisory issued Saturday January 16, 2010 at 7:00 am  

By Eric White  & Dan Towner                     

The Bottom Line:

Avalanche Danger Rating* for today:

Where: MODERATE avalanche danger, especially above tree line on easterly aspects

Primary Concern:   wind slabs near and above tree line, especially on SE/E/NE aspects 

Secondary Concern:   slabs from last storm above 7000 ft. on steep slopes

Size and Character:  medium sized wind slabs (blocky); small to medium sized soft slabs

Sensitivity to Triggering:   slabs will be hard to trigger near tree line, but continued wind loading on the upper mountain will keep those wind slabs very sensitive and easily triggered by an individual

Confidence in today's Forecast:  Moderate.  Timing and snow level with the incoming storm could vary

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 79% 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 high clouds in town and gusty S winds.  It is currently 41F in Mt. Shasta City and the barometer is dropping.   On Mt. Shasta:  In the Old Ski Bowl, we are measuring 63 inches of snow on the ground at 7600 ft. with no new snow and 1 inch of settlement over the last 24 hours.  Temperatures were between 27F last night to 36F yesterday at noon and it is currently 30F.  Winds on the S side of Mt. Shasta at 8000 ft. (Grey Butte) have averaged 15 mph over the last 24 hours and were from the SW.  Winds over the last 12 hours have increased averaging 19 mph and gusting to 35 mph from the SW.  At 6 am winds are 22-35 mph from the WSW and it is 28F.   Castle/Mt. Eddy:   On Mt. Eddy we are currently measuring 42 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 26-35F and it is currently 31F.  At Castle Lake we are measuring 33 inches of snow on the ground with no new snow and 1 inch of settlement over the last 24 hours.  Temperatures over the last 24 hours were between 29-36F and it is currently 30F. Upper air measurements this morning show temperatures a few degrees colder than yesterday.

Weather Forecast: It's exciting that winter will finally arrive, as we are expecting "typical" winter storms for our area over the next 1-2 weeks.  It looks like the first storm won't be as strong or cold as the ones following next week, but it will open the door.  Overall, it looks like central and southern California will receive more precipitation, but the whole State will be affected.  For today, we can expect moderate south winds and increasing clouds.  The beginning of the storm will be this afternoon with the snow level starting off near 6000 ft. and then lowering by tomorrow morning to around 4500-5000 ft.  We will receive around 3 inches of snow tonight and then another foot of snow on Sunday.  Snow levels will drop to town and below early next week.  Below tree line temperatures today will be in the low to mid 30's with SSE winds around 10 mph and stronger gusts.  Near and above tree line, temperatures will remain in the upper 20's to low 30's with winds around 30-40 mph from SW and stronger gusts possible.  On the upper mountain winds will be from the W moving to the SW later today at 40 mph.

Snow Pack:  Snow at lower elevations (below 6000 ft.) received rain early this week which has consolidated the snow and left us with a firm surface.  Near tree line, some packed powder exists in shady areas with crusts in open areas.  Above tree line, wind packed powder can be expected with some wind sculpting.  Thin wind slabs exist here, mostly on SE and E aspects and will be less sensitive than they were Thursday and Friday.  Winds on the upper mountain were pretty steady  all day yesterday, loading E aspects and these will remain sensitive today, so climbers should be very cautious.  As the first weak storm arrives later today, followed by plenty of snow over the next week, it will be important to see how the new snow bonds to our current snow pack.  With moderate winds expected and significant snow fall, we expect the avalanche danger to begin increasing Sunday.  Be observant snow pack conditions and changes in the weather.  

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:

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

Please report weather and snow observations:  (530)926-9614  Thanks!