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Avalanche Advisory for 2016-12-18 06:58:18

  • EXPIRED ON December 19, 2016 @ 6:58 am
    Published on December 18, 2016 @ 6:58 am
  • Issued by Nick Meyers - Shasta-Trinity National Forest

Above treeline, overall MODERATE avalanche danger exists on all aspects.  Pockets of CONSIDERABLE danger may be encountered on E-SE-S facing slopes due to recent wind loading.
Near and below treeline, the avalanche danger remains LOW.  Wind slab avalanches, confined to alpine terrain, are the primary concern for today.  Human triggered avalanches are possible and could range from small to large in size. 

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Avalanche Problem 1: Wind Slab

  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
    Historic
    Very Large
    Large
    Small

Wind transport of snow and wind slab development continue above treeline.  For today, wind slabs may vary from 6 inches to several feet thick in alpine terrain.  Visual observations are the best tool to use in determining the presence of wind slabs.  Look for smooth and rounded pillows of snow, active wind transport, and cornice formations. Sometimes, these areas of wind loaded snow sound hollow.  If you find yourself quickly transitioning from hard, scoured snow to suddenly softer snow on a leeward slope, beware. It is best to avoid these slopes today. Do not forget about Mother Nature's NEON SIGN for avalanche danger: recent avalanches! Blowing snow from WIND during or after a storm is also a red flag for potential avalanche danger.  East, southeast and south facing aspects above treeline, on slopes steeper than 35 degrees should be most suspect. Potentially prime starting zones lie just below ridgelines, in gullies, and on convex rolls. Mid-slope wind loading is possible with strong winds. 

Forecast Discussion

Clear, cold and sunny skies have been the soup de jour for this weekend. For below and near treeline terrain, rain runnels, breakable crust and hard conditions have challenged most and kept the avalanche danger low. Above treeline, conditions are different. Above 8,000 feet, temperatures have been cooler and winds have been moving snow around quite well. As you make your way up the mountain, the hard crusty snow at lower elevations certainly does not raise one's awareness for avalanche danger. However, when you get above treeline, you will need to pay attention because once again, the snow and avalanche conditions are different. Just because the sky is blue and the sun is out does NOT imply an invitation to the party.

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LOCAL AREA ROAD, NORDIC, AND SNOWMOBILE PARK STATUS:

The Sand Flat cross country ski trails are in good shape still and ready for your cross country skis and snow shoes.  These are backcountry routes marked with blue diamonds on trees.  Trails are not groomed.  Snow shoers, please blaze a parallel trail to cross country skiers staying out of the skin track.  These trails can be accessed via the Everett Memorial Highway.  Thank you, and enjoy!

The Mt. Shasta Nordic Center is CLOSED for the time being but will be opening soon! The trails are covered in snow and they are working on getting things going this month. http://www.mtshastanordic.org

The Pilgrim Creek & Deer Mountain Snowmobile Parks are open, however there is no snow at these locations currently. One must drive down the 19 road (Military Pass) for several miles to get to consistent snow before unloading. Private industry is logging out there so watch out for log trucks. Head to our "Education" tab on our website and find the snowmobile section for trail information, grooming status, and other sledder resources.

The Castle Lake Road is OPEN. The Everett Memorial Highway is OPEN. The Castle Lake and Everett Hwy are plowed year round to the trailheads. The roads are not always first priority, so your dawn patrol powder mission might be ceased if the plow has not made it up yet. Siskiyou County does a great job keeping the roads clear. Be respectful of the plow drivers if you encounter them. If you get to Bunny Flat before or during when the plow is there, please park on the uphill, LEFT side of the parking lot as you drive in. This is uphill and lookers right of the bathrooms. Thank You!

The Five Red Flags of Avalanche Danger any time of year include: 1) Recent/current avalanche activity 2) Whumphing sounds or shooting cracks 3) Recent/current heavy snowfall 4) Strong winds transporting snow 5) Rapid warming or rain on snow.

Recent Observations

Yesterday on the south side of Mt Shasta on all aspects up to approximately 7,500-8,000 feet, observations found medium to large rain runnels, firm snow, breakable crust and challenging skiing conditions. Above treeline, cold and windy weather over the past two days gave way to one large natural wind slab avalanche off Casaval Ridge and one medium size skier triggered wind slab avalanche in Sun Bowl.  (See avalanche observations with pictures below) Both aspects generally southeast facing, experienced steady northwest winds loading recent snow onto these leeward slopes. Prior snow surfaces were capped by a widespread, smooth surface crust. This smooth, icy surface provided a good bed surface for cold snow to build and eventually fail on. Evidence of blowing snow above treeline has been visible all the way from Mt Shasta City over the past two days. No signs of instability has been observed below or near treeline. 

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Have you seen our new, BIG BLUE buttons on our website? Yep, thats them, just up and to your left! You can use those and absolutely should. No more email, no more text, no more messing around! So cool. Please submit your observations by clicking either 'snowpack' or 'avalanche' observation and follow the template. Just a photo? Great! Snowpit profile? Awesome! Video, notes, weather...you name it, there is a place for it. It's simple, easy and fun and extremely useful for us and other users. We also have a drop down menu within the obs template that allows you to submit observations from "out of the forecast area". Heading to Crater Lake or Mt Lassen? Submit some obs! This will help us create the BEST possible avalanche advisory AND provide a great place for peeps to go for checking backcountry conditions. Saddle up!

 

Weather and Current Conditions

Weather Summary

Another clear and cool day for Southern Siskiyou County. Blocking high pressure that has brought our sunny albeit cold weather will persist for today. This setup will begin to break down tomorrow and bring an active weather pattern for next week. The first system will arrive on Monday. This weak front will be the start of the action. While not bringing much precipitation,  it will aid in breaking down the doors allowing for additional quick moving, low amplitude storms to move our way. It's setting up to be a white Christmas and we love that. We also love fresh snow, good skiing and most importantly... everyone staying safe in the backcountry.

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In Mt Shasta City at 0500, we have a current temperature of 21 F, the same temperature as yesterday at this time.

On Mt Shasta (South Side) in the last 24 hours...

Old Ski Bowl - 7,600 feet, the current temperature is 12F degrees F. Snow on the ground totals 70 inches with 2 inches of settlement.  Temperatures have ranged from 9F to 25F.

Grey Butte - 8,000 feet, the current temperature is 15 degrees F. Temperatures have ranged from 9 F to 20 F.  Variable winds have averaged 5-10 mph, with gusts to 21mph.

Mt Eddy Range (West side of Interstate-5)... 

Castle Lake - 5,600 feet, the current temperature is 13 degrees F. Temperatures have ranged from 9 F to 15 F. Snow on the ground totals 17 inches with little settlement.

Mt Eddy - 6,500 feet, the current temperature is 19 degrees F. Temperatures have ranged from 15 F to 22 F. Snow on the ground measures 25 inches with one inch settlement. Winds have averaged 2 mph with gusts to 13 mph, southerly.

THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 20.25 inches of water, normal is 11.48 inches, putting us at 176% of normal.  For the month of December we received 3.78 inches of water, normal is 4.12 inches, putting us at 91% of normal, and finally... for the year of 2016 we've received 53.15 inches of water, normal is 39.48 inches, putting us at 134% of normal.

Always check the weather before you attempt to climb Mt Shasta. Further, monitor the weather as you climb. Becoming caught on the mountain in any type of weather can compromise life and limb. Be prepared.

CURRENT CONDITIONS at Bunny Flat (6950 ft)
0600 temperature: 9
Max. temperature in the last 24 hours: 23
Average wind direction during the last 24 hours: Variable
Average wind speed during the last 24 hours: 0-5 mi/hr
Maximum wind gust in the last 24 hours: 10-15 mi/hr
New snowfall in the last 24 hours: 0 inches
Total snow depth: 34 inches

Two Day Mountain Weather Forecast

Produced in partnership with the Medford NWS

For 7000 ft to 9000 ft
  Sunday
(4 a.m. to 10 p.m.)
Sunday Night
(10 p.m. to 4 a.m.)
Monday
(4 a.m. to 10 p.m.)
Weather Sunny, partly cloudy in late afternoon. Partly cloudy Mostly cloudy
Temperature (°F) 32 20 38
Wind (mi/hr) East/Northeast 5-10 mph North 5-10 mph West/Northwest 10-15 mph
Precipitation SWE / Snowfall (in) / 0 / 0 / 0
For 9000 ft to 11000 ft
  Sunday Sunday Night Monday
Weather Sunny, breezy at upper elevations Partly cloudy, Blustery. Mostly cloudy, Windy.
Temperature (°F) 24 24 29
Wind (mi/hr) North 10-15 mph West/Northwest 0 West/Northwest 20-25 mph
Precipitation SWE / Snowfall (in) / 0 / 0 / 0

Disclaimer

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 on midnight of the date it was posted unless otherwise noted.