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Avalanche Advisory for 2017-01-02 07:15:35

  • EXPIRED ON January 3, 2017 @ 7:15 am
    Published on January 2, 2017 @ 7:15 am
  • Issued by Andrew Kiefer - Mt Shasta Avalanche Center

MODERATE avalanche danger exists on all aspects above treeline and near treeline.  Below treeline, LOW avalanche danger exists.  Wind slab avalanches are the primary concern today, and are most likely near and above treeline.  A winter storm is currently impacting the advisory area.  Watch for changing conditions today, and expect the avalanche danger to quickly rise as snow accumulates.

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

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.

Avalanche Problem 1: Wind Slab

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As snow continues to fall and strong westerly winds blow, wind slabs will develop.  The avalanche danger is expected to rise throughout the day today.  Wind slabs will most likely be found on all aspects above treeline, and near treeline on N, NE, E, SE, S aspects.  4-8 inches of new snow is expected by tonight, and winds may shift from the northwest to the west/southwest.  Be alert as conditions may change quickly throughout the day.  Monitor the height of new snow, and recognize how much snow is available for transport.  Blowing snow, cornice formation, textured snow surfaces, and recent tracks re-filling quickly with snow are all indications of changing conditions and potential wind slab development.

Forecast Discussion

A winter storm began yesterday, and will continue to impact the area over the next few days.  As of this morning, snowfall totals are a trace to one inch.  So far, this storm has done little to change conditions.  Several inches of new snow, and strong winds are expected today, however.  As snow accumulates and winds blow, wind slabs will develop, and the avalanche danger will quickly rise.  The presence and sensitivity of the wind slab problem will be dependent on snowfall totals.  Already, winds have been strong out of the northwest, and are expected to shift to the west/southwest.  Monitor conditions as they change today.

In addition to the wind slab problem, two other problems are expected to develop if we receive several inches of new snow.  The first is a storm slab problem.  At all elevations and on all aspects, the new snow may likely accumulate enough to form a cohesive slab sitting on top of the old snow surface.  Watch for this problem by the end of today, and expect this to be a concern if the forecasted snow totals verify.

Finally, a persistent slab avalanche problem may become reactive if enough weight is added to the snowpack with the incoming storm snow (see video in Observations below).  On 12/23, a weak layer was buried by our last storm event, and now exists on cold, shady aspects (NW, N, NE, E) throughout the advisory area.  This layer exists as rounding facets buried one foot below the snow surface right now, and in many locations has been found to sit below a crust.  No avalanches have occurred on this layer, but recent stability tests show unstable results.  On W, SW, S, SE slopes, the 12/23 layer does not present as weak snow and does not seem to pose a future problem.

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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

This morning, our remote weather stations reported a trace to 1 inch of new snow. Moderate to strong northwest winds blew, and temperatures were in the single digits and low teens.  The new snow is falling on variable old snow surfaces.  In upper elevation terrain, surface conditions are wind scoured, firm, and icy.  Snow surfaces near and below treeline hold wind scoured snow, breakable crust, and cold dry snow on shady slopes protected from the wind.

Yesterday, during a snowmobile tour on the west side of Mount Eddy, the sky was fully covered throughout the majority of the day and temperatures were in the teens.  Breaks in the clouds, and sporadic precipitation occurred. Moderate to strong northwest winds were steady, and significant evidence of wind-affected snow was found near and above treeline. Snow coverage was good on Park’s Creek Road above 5,600ft.   

A test pit dug yesterday during the tour in the Eddy Range targeted the 12/23 layer (see video in Observations below).  This layer was buried 1ft/30cm down from the snow surface and was reactive in stability tests.  The 12/23 layer has presented as weak snow sitting below a crust on shady, cold slopes (NW,N,NE,E).  At yesterday's test pit location on a north facing slope at 7800ft, the 12/23 layer presented as rounding facets and the crust was absent.  As weight is added to the snowpack with the incoming storms, this layer may loose strength, and a persistent slab avalanche problem may become a concern in the advisory area.    

Weather and Current Conditions

Weather Summary

Yesterday and overnight, our advisory area picked up a trace to 1 inch of new snow.  Snow totals during this time fell short of the forecasted amounts, and delays and breaks in the storm have occurred.  Winds have blown steady out of the northwest during the past 24 hours, and are expected to shift to the west/southwest today.  Temperatures will reach highs in the upper teens, with wind chills dropping to negative values above 6000ft as a cold front remains in the area.

An upper level trough and a surface low moving off of the Southern Oregon coast will bring periods of heavy snow to Siskiyou County.  Freezing levels will be near 1000ft.  4-8 inches of new snow are forecast for today, with snowfall expected to continue tonight and through the week.   

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In Mt Shasta City at 0500, we have a current temperature of 25 F.

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

Old Ski Bowl - 7,600 feet, the current temperature is 8 degrees F. Snow on the ground totals 70 inches with no new snow and little settlement.  Temperatures have ranged from 8 F to 20 F.

Grey Butte - 8,000 feet, the current temperature is 8 degrees F. Temperatures have ranged from 7 F to 14 F.  Winds have averaged 20-30 mph with gusts to 56 mph, blowing from the northwest.

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

Castle Lake - 5,600 feet, the current temperature is 14 degrees F. Temperatures have ranged from 14 F to 26 F. Snow on the ground totals 27 inches with 1 inch of new snow.

Mt Eddy - 6,500 feet, the current temperature is 12 degrees F. Temperatures have ranged from 11 F to 20 F. Snow on the ground measures 32 inches with 1 inch of new snow.  Winds have averaged 2 mph with gusts to 14 mph, blowing from the southeast.

THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 21.16 inches of water, normal is 15.45 inches, putting us at 137% of normal.  For the month of January we received a trace amount of water, normal is .24 inches, and finally... for the year of 2017 we've received a trace amount of water, normal is .24 inches.

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: 12
Max. temperature in the last 24 hours: 23
Average wind direction during the last 24 hours: Northwest
Average wind speed during the last 24 hours: 20-25 mi/hr
Maximum wind gust in the last 24 hours: 50 mi/hr
New snowfall in the last 24 hours: trace inches
Total snow depth: 40 inches

Two Day Mountain Weather Forecast

Produced in partnership with the Medford NWS

For 7000 ft to 9000 ft
  Monday
(4 a.m. to 10 p.m.)
Monday Night
(10 p.m. to 4 a.m.)
Tuesday
(4 a.m. to 10 p.m.)
Weather Snow showers. Chance of precipitation is 80%. Snow showers. Chance of precipitation is 80%. Snow showers likely. Chance of precipitation is 70%.
Temperature (°F) 18 13 22
Wind (mi/hr) South 10-15 mph South 15-20 mph Southeast 10-15 mph
Precipitation SWE / Snowfall (in) / 4-8 / 3-7 / 4-8
For 9000 ft to 11000 ft
  Monday Monday Night Tuesday
Weather Snow showers and windy. Chance of precipitation is 80%. Snow showers and windy. Chance of precipitation is 80%. Snow showers likely and windy. Chance of precipitation is 70%.
Temperature (°F) -2 -2 14
Wind (mi/hr) Southwest 30-40 mph West/southwest 4-8 Southwest 40-50 mph
Precipitation SWE / Snowfall (in) / 4-8 / 3-7 / 3-7

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.