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Avalanche Advisory for 2017-01-07 07:06:44

  • EXPIRED ON January 8, 2017 @ 7:06 am
    Published on January 7, 2017 @ 7:06 am
  • Issued by Andrew Kiefer - Mt Shasta Avalanche Center

CONSIDERABLE avalanche danger exists on all aspects and at all elevations.  A Winter Storm Warning is in effect until 10pm this evening, and the avalanche danger will increase as snow accumulates.  Wind slabs avalanches are the primary concern, and can be found near and above treeline on NW-N-NE-E-SE aspects.  Persistent slab avalanches on NW-N-NE-E aspects near and below treeline are a concern as well  Today, natural avalanches are possible, and human triggered-avalanches are likely.

Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

Avalanche Problem 1: Wind Slab

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With existing snow on the ground available for transport, and a significant amount of new snow associated with south/southwest winds expected today, wind slabs are the primary avalanche concern.  The likelihood of triggering a wind slab will increase throughout the day as snow accumulates.  Existing wind slabs are already 2-4ft deep, and wind slab thickness will only grow.  Wind slabs are distributed throughout the terrain on lee slopes and cross-loaded features near and above treeline.  NW-N-NE-E-SE are the slope aspects where the wind slab problem exists. 

Natural wind slab avalanches are possible today, and human triggering is likely.  Watch for blowing snow, cornice formation, pillows of loaded snow, and abrupt transitions from shallow areas of snow to areas of deeper snow.  Avoid slopes steeper than 35 degrees where these conditions are present.

Avalanche Problem 2: Persistent Slab

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A weak layer of snow was buried on 12/23.  The Christmas and New Years storms added 2-3ft of snow and weight on top of this layer, but no avalanches occurred.  With the addition of new snow today and tonight, the 12/23 layer may reach its tipping point. 

This avalanche problem has a specific distribution to near and below treeline elevations, and NW-N-NE-E aspects.  Despite the lack of avalanche activity, this avalanche problem cannot be ignored.  Uncertainty exists as to how the 12/23 layer will behave in the near future.  For the past 2 weeks, stability tests targeting this layer have been inconsistent.  On several occasions however, stability test results have produced unstable results, and our persistent slab avalanche problem remains a concern. 

Forecast Discussion

The National Weather Service has issued a Winter Storm Warning in effect until 10pm tonight.  10-14 inches of new snow is expected to fall today, and the avalanche danger will quickly rise as snow accumulates.  Wind slab avalanches are the primary concern, and an isolated persistent slab avalanche problem remains a concern as well.  In addition, if the projected snow totals verify, loose dry avalanches and storm slab avalanches will likely develop as problems on all aspects and at all elevations.

By the afternoon today, dangerous avalanche conditions will exist in the backcountry. Carful snowpack evaluation, cautious route finding, and conservative decision-making are essential.  Monitor conditions as they change, and adjust your backcountry travel plans accordingly.

Reminders! Companion Rescue clinic today at 9am.  Meet at The Fifth Season and come prepared to be outside.  Also, the Backcountry Film Festival, a fundraiser for the Mt Shasta Nordic Center, is Tonight! Check their website for details. (www.mtshastanordic.org

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LOCAL AREA ROAD, NORDIC, AND SNOWMOBILE PARK STATUS:

The Sand Flat cross country ski trails are in good shape 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 OPEN for the season! Take advantage of this wonderful venue. Groomed trails accomodate both classic and skate skiing styles. Rentals available. Visit their website for more details.  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

No avalanches have been observed since the most recent storm event ending on January 4th.  Clear, cold weather was in place yesterday.  The snowpack has experienced several inches of settlement over the past few days. As of 5am this morning, 2-3 inches of new snow has fallen throughout the advisory area and south/southwest winds continue to blow.

During a tour on Left Peak in the Castle Lake are yesterday, strong south/southwest winds were observed transporting snow near and above treeline.  The snow surface has become noticeably more supportable due to snowpack settlement, but plenty of snow was available for transport.  In exposed areas at all elevations, evidence of wind effect was observed.  A test pit dug on a NW slope at 5800ft revealed poor snowpack structure.  The Christmas and New Years storm events have created a stiff slab 2-3ft thick.  This slab sits on a crust capping weak, unconsolidated snow in many places – the 12/23 persistent weak layer.  Despite poor snowpack structure, no significant signs of instability were observed, and no propagation occurred in Extended Column Tests.

Weather and Current Conditions

Weather Summary

A warm front is currently moving through the advisory area, mixing with cold artic air already in place.  Snowfall began at midnight, and Mount Shasta City and our remote weather stations recorded 2-3 inches of new snow as of 5am this morning.  Up to 1 inch of Snow Water Equivalent (SWE) and 10-14 inches of new snow is expected today.  Freezing levels will remain near 1000ft throughout this morning and afternoon, and will rise rapidly to 5000ft by late tonight.  High temperatures for today will be in the low 30’s.  Winds will be southerly, blowing 15-25mph with gusts up to 50mph.

Tonight will bring more snow before a transition to rain and mixed precipitation.  A warming trend will occur, and freezing levels will rise to 7500ft tomorrow.  Several inches of new snow are expected to fall overnight.  Freezing levels will determine exact snowfall totals, but cold upper elevation terrain may receive over 2 feet of new snow by Monday.  An additional series of wet storms will bring precipitation and varying freezing levels to the area through the next week.

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In Mt Shasta City at 0500, we have a current temperature of 30 F with 2 inches of new snow.

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

Old Ski Bowl - 7,600 feet, the current temperature is 19 degrees F.  Temperatures have ranged from 16 F to 26 F. Snow on the ground totals 89 inches with 3 inches of new snow. 

Grey Butte - 8,000 feet, the current temperature is 16 degrees F. Temperatures have ranged from 14 F to 25 F.  Winds have averaged 10-15 mph with gusts to 21 mph, blowing out of the west/southwest.

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

Castle Lake - 5,600 feet, the current temperature is 22 degrees F. Temperatures have ranged from 14F to 24 F. Snow on the ground totals 47 inches with 2 inches of new snow.

Mt Eddy - 6,500 feet, the current temperature is 21 degrees F. Temperatures have ranged from 15 F to 28 F. Snow on the ground measures 48 inches with 2 inches of new snow.  Winds have averaged 2-4 mph with gusts to 11 mph, blowing southwest in direction.

THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 22.56 inches of water, normal is 16.62 inches, putting us at 136% of normal.  For the month of January and for the year of 2017, we received 1.40 inches of water, normal is 1.41 inches, putting us at 99% 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: 19
Max. temperature in the last 24 hours: 26
Average wind direction during the last 24 hours: West/Southwest
Average wind speed during the last 24 hours: 5-10 mi/hr
Maximum wind gust in the last 24 hours: 20 mi/hr
New snowfall in the last 24 hours: 1 inches
Total snow depth: 52 inches

Two Day Mountain Weather Forecast

Produced in partnership with the Medford NWS

For 7000 ft to 9000 ft
  Saturday
(4 a.m. to 10 p.m.)
Saturday Night
(10 p.m. to 4 a.m.)
Sunday
(4 a.m. to 10 p.m.)
Weather Heavy Snow and Breezy. Heavy Snow and Breezy. Rain and Snow. Then heavy rain after 10am.
Temperature (°F) 32 30 38
Wind (mi/hr) South/southeast 15-25 mph South/southeast 15-20 mph South 20-30 mph
Precipitation SWE / Snowfall (in) / 10-14 / 7-11 / 0
For 9000 ft to 11000 ft
  Saturday Saturday Night Sunday
Weather Heavy Snow and Windy. Heavy Snow and Windy. Heavy Snow and Windy.
Temperature (°F) 24 20 28
Wind (mi/hr) Southwest 25-30mph South 11-17 Southwest 40-50 mph
Precipitation SWE / Snowfall (in) / 11-17 / 19-25 / 20-25

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.