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Avalanche Advisory for 2016-03-25 07:01:34

  • EXPIRED ON March 26, 2016 @ 7:01 am
    Published on March 25, 2016 @ 7:01 am
  • Issued by Nick Meyers - Shasta-Trinity National Forest

Over the past 48 hours, strong northwest flow aloft has created pockets of unstable snow near and above treeline. Human triggered wind slabs along ridgelines, bowls, near rock outcroppings and steep chutes are possible. MODERATE avalanche danger with isolated areas of CONSIDERABLE danger exist for these wind loaded pockets on SW-S-SE-E-NE facing slopes. Later in the day, MODERATE danger is possible for loose-wet related instabilities on south and east aspects, below and near treeline.

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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Continued, strong northwest flow will again blow snow around today and could create new wind slabs or build on the past 48 hour slabs on leeward SW-S-SE-E-NE facing slopes. The northwesterlies will prevail through Saturday morning. Ridgelines, depressions, moraine convexities, rock outcroppings, steep and narrow couloirs are all great places for wind to form eddies and snow to stack up. Wind can load slopes 10x faster than snow falling from the sky... and even though it's not snowing out and the sky may be blue, wind slabs are still possible. For exposed ridgelines where wind speeds are greatest, non-typical starting zones might exist where wind has blown snow down further on the slope... mid-slope starting zones, as opposed to classic ridgeline wind loading.  Ridgelines are likely scoured completely, but be careful near the edge of leeward slopes...cornices may have built up and also, just over the edge is where perhaps an unstable pocket of wind loaded snow might lurk. The most concern for these potentially unstable pockets of wind loading will be above treeline on Mt Shasta. Also be cautious near treeline where wind can still be present.

Avalanche Problem 2: Loose Wet

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Loose wet instabilities will be minimal today. However, warming temps over the next 48 hours will likely create some loose wet roller balls, pin wheels and perhaps larger slides on the lower flanks of Mt Shasta and other warm, lower elevation, open aspects in the forecast area. If you see slopes that are shedding snow, this is a good sign that larger slides are possible. That is your que to move to shadier slopes or come back another day. Wet loose slides are particularly dangerous when paired with a terrain trap such as melting lake edges, a gully, a crevasse or trees. Spring is almost here and wet loose instabiliites will need to be on your mind during rapid warming, poor overnight re-freezes, and hot, sunny days.

Forecast Discussion

The region will see a gradual move toward some wintery weather for Easter weekend, but not before a brief warming trend. Today, partly cloudy skies with gusty northwest winds continuing above treeline. A warm front moving in later today will allow for warmer daytime highs tomorrow... this will be soon followed by a cold front that will drop temperatures significantly for a cool Easter. Along with this, some light precipitation is expected that could bring several inches of snow to the mountains. Snow levels will begin on Sunday around 4-5,000 feet and lower to 2-3,000 feet by Monday. Overall, expect scattered showers for Sunday and Monday. Snow accumulation will not be much in town due to warm ground temperatures. As for the wind... we will get short breaks here and there however it looks to remain windy on Shasta for the foreseeable future.

THIS SEASON PRECIPITATION for MT SHASTA CITYSince October 1st (the wet season), we have received 36.72 inches of water, normal is 34.5 inches, putting us at 106% of normal.  For the month of March we've received 11.20 inches of water, normal is 5.0 inches, putting us at 224% of normal, and finally... for the year of 2016 we've received 27.23 inches of water, normal is 19.29 inches, putting us at 141% of normal.

Recent Observations

Since the morning of the 23rd, the northwest winds have been howling on the mountain and transporting a lot of snow onto leeward south, southeast, east and northeast aspects. While yes wind loading on these aspects is certain, much of the snow (as visible in the photo below) has also likely been blown away. While it has been windy on the mountain, other locations in the forecast area have been less windy and warmer. The Castle Lake area reported "well done" corn on south and east aspects by 10am yesterday. Temps at Castle rose to 52 degrees and tomorrow they should be even warmer. This has and will create loose wet instabilities like roller balls and pinwheels, with the chance of larger loose wet slides possible. Further observations at Castle Lake noted melting lake edges. This is actually a serious concern... if one gets caught or knocked off their feet in any type of avalanche and the slide makes it's way down to lake level... well, lets just say it's very difficult if not impossible to dig somebody out from underneath slushy water. In other words, melting lake edges are horrible terrain traps! Be careful up there.

On the mountain, the snow is still in a transitional state. Yesterday a local observer toured up to the Sun Bowl area. High winds were obvious due to visible snow transport at all elevations above treeline. South, southeast and east aspects were most notably wind loaded. Winds below treeline were much less, 5 mph/G-15 mph. The snow near and below treeline on southerly aspects was soft and isothermic. Snow on ridgetops, windward slopes and in the shadows remained firm. On the Sun Bowl bench, just above treeline, wind speeds were estimated at a sustained 35 mph with gusts to 40 mph and on Green Butte proper, 50+ mph, northwest. A snowpit on a S/SE slope, 37 degrees,  found a total "new" snow depth of 46cm down to the old snow surface. The upper 4cm of the surface comprised of a crust. Solar radiation has been effective at softening the upper portion of crust but has not been significant enough for a ski to penetrate while making turns. Below the surface crust, lighter density, rounding snow grains exist. The old snow is a bullet proof, knife hardness melt-freeze crust. One ECTN16 test at 17 cm down was due to a density change in the snow from pencil hardness to one finger. While a slab is not expected to fail here, it could be the depth where wet slides may be triggered with Saturday's warming.

Northwest winds on Mt Shasta and snow transport! Photo taken from Mt Shasta City on 3.24.16 by T Belton.

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!

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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 Everitt Memorial Highway is OPEN. The Castle Lake and Everitt 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 and 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.

Weather and Current Conditions

Weather Summary

Good Morning! In Mt Shasta City at 0500, we have a current temperature of 37 F, the same temperature as yesterday at this time. Skies are partly cloudy with calm wind.

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

Old Ski Bowl - 7,600 feet, the current temperature is 37 degrees F. Snow on the ground totals 159 inches with no new snow and 3 inches of settlement.  Temperatures have ranged from 32 F to 44 F.

Gray Butte - 8,000 feet, the current temperature is 36 degrees F. Temperatures have ranged from 29 F to 39 F. The northwest wind has continued, averaging 20-30 mph with gusts to 50 mph in the last 24 hours.

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

Castle Lake - 5,600 feet, the current temperature is 30 degrees F. Temperatures have ranged from 30 F to 42 F. Snow on the ground totals 76 inches with no new snow and 1 inch settlement.

Mt Eddy - 6,500 feet, the current temperature is 32 degrees F. Temperatures have ranged from 30 F to 42 F. Snow on the ground measures 88 inches with no new snow and 2.5 inches of settlement. Winds have been south east in nature with an average of 2-3 mph, and a maximum gust of 11 mph.

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: 34
Max. temperature in the last 24 hours: 45
Average wind direction during the last 24 hours: Northwest
Average wind speed during the last 24 hours: 10-15 mi/hr
Maximum wind gust in the last 24 hours: 49 (Gray Butte) mi/hr
New snowfall in the last 24 hours: 0 inches
Total snow depth: 102 inches

Two Day Mountain Weather Forecast

Produced in partnership with the Medford NWS

For 7000 ft to 9000 ft
  Friday
(4 a.m. to 10 p.m.)
Friday Night
(10 p.m. to 4 a.m.)
Saturday
(4 a.m. to 10 p.m.)
Weather Mostly sunny, with a high near 43. North northwest wind 10-15 mph. Mostly clear, with a low around 29. North northwest wind 10-15 mph. A slight chance of rain and snow after noon. Partly sunny, with a high near 48. Northeast wind 5-10 mph Chance of precipitation is 20%.
Temperature (°F) 43 29 48
Wind (mi/hr) North/Northwest 10-15 mph North/Northwest 10-15 mph Northwest, becoming northeast 5-10 mph
Precipitation SWE / Snowfall (in) / 0 / 0 / 0
For 9000 ft to 11000 ft
  Friday Friday Night Saturday
Weather Mostly sunny, with a high near 25. Windy, with a north northwest wind 30 to 40 mph Mostly clear, with a low around 25. Windy, with a north wind 30 to 40 mph A 20 percent chance of snow after 11am. Partly sunny, with a high near 26. Windy, with a north northwest wind 20 to 30 mph, decreasing
Temperature (°F) 25 25 26
Wind (mi/hr) North/Northwest 30-40 mph with gusts higher in exposed areas North 0 North/Northwest 20-30 mph with gusts higher in exposed areas
Precipitation SWE / Snowfall (in) / 0 / 0 / 0-1

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.