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Avalanche Advisory for 2016-03-22 07:01:57

  • EXPIRED ON March 23, 2016 @ 7:01 am
    Published on March 22, 2016 @ 7:01 am
  • Issued by Jon Dove - Shasta-Trinity National Forest

MODERATE avalanche danger exists on all aspects and elevaitons, slopes 35 degrees and steeper for newly formed storm and wind slabs.  Storm slabs will be most prevalent near and below treeline in wind protected areas. Pockets of CONSIDERABLE danger remain on wind loaded, leeward NW-N-NE-E-SE aspects near and above treeline.  Human trigger of wind slabs may be possible. Evaluate the snowpack and terrain careully before committing to a slope. Conservative decision making is essential.
 

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.

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

Avalanche Problem 1: Wind Slab

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Wind slabs that developed with yesterday's storm will continue to be a concern for backcountry travelers today near and above treeline. New snow amounts of 7-12 inches have graced our forecast area providing plenty of loose dry snow to transport.  Wind slabs and pillows were found yesterday on Gray Butte near treeline, and were easily triggered on test slopes.  Slab formations of up to 1-2 feet thick can be found elsewhere.  These may still be sensitive to human trigger, and caution should be taken when encountered.  They will be found on wind loaded, leeward NW-N-NE-E-SE aspects in the typical starting zones along ridge tops, around rock outcroppings, the tops of chutes and couloirs, and gullies.  Due to the strong nature of the winds, slabs may develop in non-typical ares such as mid-slope depressions, or along the leeward sides of moraines.  Visibility will possibly improve later today allowing folks to opportunity to venture above treeline into areas where wind slabs, pillows, and drifts are more prevalent.  Choose your route carefully, and evaluate the snow and terrain with caution before committing to a path. 

Avalanche Problem 2: Storm Slab

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Yesterday's storm did not disappoint bringing a fair amount of snow to our forecast area.  New snow amounts of up to a foot were recorded building soft slabs in areas free of the wind's affect.  Lingering soft storm slabs will remain a concern for today near and below treeline in areas that were protected from moderate southerly to west/northwest winds.  The moderate to strong winds, and the light nature of the new snow will have limited the formation of storm slabs above treeline.  Use caution on slopes 35 degrees and steeper in areas where soft slabs may still exist.

 

Avalanche Problem 3: Loose Dry

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Loose dry sloughs were easily triggered on slope 37 degrees and steeper yesterday.  Temperatures are set to warm up today, but shaded northerly facing aspects will remain cool enough for loose dry instabilities to persist.  We received 7-12 inches of new, relatively light and dry, snow yesterday.  Enough snow could be entrained in a slough slide to push someone into undesirable terrain such as over a cliff band, into rocks, or strained through trees.  Therefore, loose dry slough will remain a potential hazard to backcountry travelers. Ski/ride on steep northerly slopes with caution, and have a way to avoid sloughs as you descend.

Forecast Discussion

Yesterday's storm delivered a generous helping of snow and rain to the Mount Shasta area.  The cool temperatures kept snow levels low at around 4,000 feet.  Anywhere from 7-12 inches of snow fell over the forecast area heightening the avalanche danger for storm slabs, wind slabs, and loose dry sloughing snow.  These avalanche problems will persist for today, but will become less of an issue for backcountry travelers over the coming days.  We are making a transition into a more dry and warmer weather pattern for the remainder of the week. Clouds and some scattered lingering showers will begin to move toward the east by this afternoon, and begin to break up over our area.  We might even see some sun poking through here and there later today.  By Wednesday things will quiet down as high pressure pushes in, and an upper level ridge builds aloft. The edge of a weak front will skim past our area late Wednesday night into early Thursday morning before clearing out for the remainder of the week. Any precipitation with this system will be light to non-existent.  Precipitation models show zero's for the next four days.  West/northwest winds will remain moderate to strong at mid-mountain to upper elevations (10,000 feet and up) with gusty ridge top winds. Speeds of 25-35 mph with higher gusts should be expected.  Rock outcroppings at higher elevations have become entombed in rime ice.  Climbers should keep their heads up for falling ice, especially as the day begins to warm up. 

THIS SEASON PRECIPITATION for MT SHASTA CITYSince October 1st (the wet season), we have received 36.72 inches of water, normal is 34.04 inches, putting us at 107% of normal.  For the month of March we've received 11.20 inches of water, normal is 4.54 inches, putting us at 246% of normal, and finally... for the year of 2016 we've received 27.23 inches of water, normal is 18.83 inches, putting us at 144% of normal.

Recent Observations

Observations were made yesterday from a ski tour up Gray Butte. Snow was falling, heavy at times, for the majority of the day.  The most snow was accumulating on open slopes that were free of the wind, near treeline.  It was in these locations that the most new snow could be found, measuring around 12 inches in depth.  Wind effected snow formations were found as well, and tested for sensitivity.  A soft wind pillow test slope proved to be easily triggered on a test slope (see photo).  Wind slabs that developed yesterday may remain sensitive to human trigger today.  By mid-day the temperatures began to warm, and heavy clouds produced a mist effect.  This impacted the new snow by making it heavier, more cascade like (think light mashed potatoes).  Temperatures are expected to be a couple of degrees warmer than yesterday, and warmer still tomorrow.  This will allow the new snow to begin to settle and bond. That being said, wind slabs will still be a concern as an avalanche problem for today near and above treeline.  Soft storm slabs may linger in areas near and below treeline that were protected from the moderate southerly to west/northwest winds.   For today, use caution and evaluate the snowpack and terrain you choose to travel on or under. Identify features of concern and avoid them, especially around leeward slopes near and above treeline. 

Avalanche danger will change as high pressure brings sun and warmer temperatures this week.  We may even see some sun later today as lingering clouds and scattered showers dissipate over the area.   

A note for all climbers and skiers heading up onto the upper mountain: Rime ice has formed on most rock outcroppings and is currently very thick. As warm days ensue, rime ice will flake off and fall down onto the slopes below. Rime ice chunks can be very large and very hard, enough to potentially kill you or cause serious injury. Beware of this hazard. Keep your eyes up slope as you climb and move laterally to avoid falling chunks of ice.  If continuous ice fall is encountered turn around and descend to climb another day!

Small wind pillow test slope, SSE aspect on Gray Butte 3.21.2016:

LEFT: Wild, wind sculpted snow on top of Green Butte, South side, Mt Shasta on 3.19.16. Wind features like this can be found throughout the forecast area. RIGHT: Widespread melt runnels, 3.19.16


 

 

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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! These beautiful, groomed trails can be accessed via the Ski Park Highway. http://www.mtshastanordic.org

The Pilgrim Creek & Deer Mountain Snowmobile Parks are open!  Trails have not been groomed in the past week and a half due to constant deep snow fall.  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 plowed to Bunny Flat and currently mostly snow free until about Red Fir Flat up.

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.

Weather and Current Conditions

Weather Summary

Good Morning! In Mt Shasta City at 0500, we have a current temperature of 35 F, 4 degrees cooler than yesterday at this time. Skies are mostly cloudy, with light precipitaiton and calm wind.

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

Old Ski Bowl - 7,600 feet, the current temperature is 18 degrees F. Snow on the ground totals 167 inches with 12 inches of new snow and 1 inch of settlement.  Temperatures have ranged from 18 F to 27 F.

Gray Butte - 8,000 feet, the current temperature is 16 degrees F. Temperatures have ranged from 16 F to 25 F. Winds were southerly yesterday until mid-afternoon, then switched to west/northwest, averaging 15-20 mph with a gust to 42 mph WNW.

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

Castle Lake - 5,600 feet, the current temperature is 23 degrees F. Temperatures have ranged from 23 F to 35 F. Snow on the ground totals 81 inches with 8 inches of new snow and little settlement.

Mt Eddy - 6,500 feet, the current temperature is 20 degrees F. Temperatures have ranged from 20 F to 29 F. Snow on the ground measures 95 inches with 7 inches of new snow and 1 inch of settlement. Winds have been southerly in nature with an average of 2 mph, and a maximum gust of 13 mph, SSE.

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: 22
Max. temperature in the last 24 hours: 31
Average wind direction during the last 24 hours: south->west/northwest
Average wind speed during the last 24 hours: 15-20 mi/hr
Maximum wind gust in the last 24 hours: 42 (Gray Butte) mi/hr
New snowfall in the last 24 hours: 9 inches
Total snow depth: 110 inches

Two Day Mountain Weather Forecast

Produced in partnership with the Medford NWS

For 7000 ft to 9000 ft
  Tuesday
(4 a.m. to 10 p.m.)
Tuesday Night
(10 p.m. to 4 a.m.)
Wednesday
(4 a.m. to 10 p.m.)
Weather Mostly cloudy with a 60% chance of snow showers Partly cloudy with a 30% chance of snow showers before 11 pm Partly sunny
Temperature (°F) 35 22 43
Wind (mi/hr) West 10-15 mph with gusts up to 30 mph this morning Northwest 5-10 mph North 5-10 mph
Precipitation SWE / Snowfall (in) / 1-3 / 0 / 0
For 9000 ft to 11000 ft
  Tuesday Tuesday Night Wednesday
Weather Mostly cloudy with a 90% chance of snow showers. Windy with wind chill values as low as -20 Partly cloudy with a 30% chance of snow showers before 11 pm. Windy with wind chill values as low as -15 Partly sunny. Windy with wind chill values as low as -6
Temperature (°F) 10 10 24
Wind (mi/hr) West 25-30 mph with gusts to 45 mph North 1-3 Northwest 15-20 mph
Precipitation SWE / Snowfall (in) / 1-3 / 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. This advisory describes general avalanche conditions and local variations always occur. You may find different conditions in the back country and should travel accordingly. This advisory expires 24 hours after the posted time unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.