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Avalanche Advisory for 2016-12-17 06:35:49
- EXPIRED ON December 18, 2016 @ 6:35 amPublished on December 17, 2016 @ 6:35 am
- Issued by Andrew Kiefer - Mt Shasta Avalanche Center
Bottom Line
MODERATE avalanche danger exists on all aspects above treeline. Near and below treeline, the avalanche danger will be LOW today. Wind slab avalanches, confined to specific features in alpine terrain, are the primary concern. Above treeline, human triggered avalanches remain possible. Near and below treeline, natural and human triggered avalanches are unlikely.
Avalanche Problem 1: Wind Slab
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Character ?
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Aspect/Elevation ?
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Likelihood ?CertainVery LikelyLikelyPossible
Unlikely -
Size ?HistoricVery LargeLargeSmall
Wind transport of snow, and wind slab development continue above treeline. For today, pockets of wind slab 1-2ft thick may exist on specific features in alpine terrain. We cannot rule the wind slab problem out yet. 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. On slopes steeper than 35 degrees just below ridgelines, in gullies, and on convex rolls are where a skier or rider is most likely to trigger a lingering wind slab avalanche today.
Forecast Discussion
All recent avalanche activity was confined to upper elevation, alpine terrain and occurred during the storm cycle ending on Thursday. Our snowpack has adjusted well to the recent load of new snow, and snowpack stability is very good near and below treeline. Following the recent storm, very cold temperatures solidified the wet, heavy snow creating variable snow surfaces. Chalky soft snow, breakable crust, and firm icy conditions all may be encountered today. Generally safe avalanche conditions exist in lower elevation terrain, and both natural and human triggered avalanches are unlikely. Above treeline, human triggered wind slab avalanches remain possible on specific terrain features.
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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
Evidence of blowing snow was observed on Ash Creek Butte yesterday. With moderate to strong westerly winds, easterly aspects above treeline were most subject to wind loading. A very shallow pocket of wind loaded snow failed (shooting cracks) on a test slope while skinning along a ridgeline yesterday (see photo in Observations below).
Overall, snowpack stability was very good near and below treeline. The recent storm ending on 12/15 added 1-2ft of wet, heavy snow to the snowpack in areas 7000ft and above. Free water was also introduced to the snowpack by way of rain and snow surface melting. Evidence of this can be found at and near the snow surface up to 8000ft in the form of a melt freeze crust and rain runnels (water drainage channels). Near and below treeline, this new snow bonded well to the old snow surface, and no recent avalanche activity was observed or reported within these elevation bands.
A test pit dug yesterday on a NE aspect at 7400ft in the east bowl of Ash Creek Butte indicated good snowpack structure. Additionally, snowpack tests showed that it is unlikely for a fracture to initiate or to propagate on the old snow/new snow interface, or on deeper layers within the snowpack.
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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
A long wave ridge of high pressure builds from the southwest, and flow will shift to the northwest as the day progresses. Very cold temperatures will start the weekend off, and dry conditions are expected to last through Monday. Daytime temperatures will be 5-10 degrees below average, and the temperature trend should gradually warm throughout the weekend. Monday night and Tuesday will bring the next chance for precipitation, as a fairly wet system will move through the area.
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In Mt Shasta City at 0500, we have a current temperature of 21 F, eleven degrees cooler than yesterday at this time.
On Mt Shasta (South Side) in the last 24 hours...
Old Ski Bowl - 7,600 feet, the current temperature is 10F degrees F. Snow on the ground totals 72 inches with 2 inches of settlement. Temperatures have ranged from 8F to 25F.
Grey Butte - 8,000 feet, the current temperature is 10 degrees F. Temperatures have ranged from 8 F to 23 F. Southerly winds have averaged 5-10 mph, with gusts to 15-20mph.
Mt Eddy Range (West side of Interstate-5)...
Castle Lake - 5,600 feet, the current temperature is 11 degrees F. Temperatures have ranged from 11 F to 20 F. Snow on the ground totals 17 inches with little settlement.
Mt Eddy - 6,500 feet, the current temperature is 16 degrees F. Temperatures have ranged from 11 F to 18 F. Snow on the ground measures 26 inches with little settlment. Winds have averaged 2 mph out of the southeast, with gusts to 10-15 mph.
THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 20.25 inches of water, normal is 11.20 inches, putting us at 181% of normal. For the month of December we received 3.78 inches of water, normal is 3.84 inches, putting us at 98% of normal, and finally... for the year of 2016 we've received 53.15 inches of water, normal is 39.20 inches, putting us at 136% 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.
| 0600 temperature: | 7 |
| Max. temperature in the last 24 hours: | 21 |
| Average wind direction during the last 24 hours: | S |
| 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: | 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 | |||
|---|---|---|---|
|
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 | Sunny | Mostly clear | Mostly Sunny |
| Temperature (°F) | 25 | 15 | 33 |
| Wind (mi/hr) | North/Northwest 10-15 mph | North/Northeast 10-15 mph | North 10-15 mph |
| Precipitation SWE / Snowfall (in) | / 0 | / 0 | / 0 |
| For 9000 ft to 11000 ft | |||
| Saturday | Saturday Night | Sunday | |
| Weather | Sunny and Windy | Mostly Clear and Windy. | Mostly Sunny and Windy |
| Temperature (°F) | 15 | 11 | 15 |
| Wind (mi/hr) | North/Northwest 30-40 mph | North 0 | Northwest 40-45, increasing to 50-55 |
| Precipitation SWE / Snowfall (in) | / 0 | / 0 | / 0 |
