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Avalanche Advisory for 2016-12-10 06:30:54
- EXPIRED ON December 11, 2016 @ 6:30 amPublished on December 10, 2016 @ 6:30 am
- Issued by Nick Meyers - Shasta-Trinity National Forest
Bottom Line
Wind slab avalanches are our primary avalanche problem. Below and near treeline, expect LOW avalanche danger due to warm temperatures and recent rain on snow. Above treeline, a human triggered old and/or new wind slab is possible and MODERATE danger will preside. Strong, westerly winds and 5-6 inches new snow could create new wind slabs on NE-E-SE slopes. Older slabs could be several feet thick. Use safe travel habits, careful snowpack evaluation and conservative decision making!
Avalanche Problem 1: Wind Slab
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Likelihood ?CertainVery LikelyLikelyPossible
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The primary concern for today will be for newly formed wind slabs from the 5-6 inches of new snow received overnight and associated winds. Strong, westerly winds will prevail for today and tomorrow, blowing 40-50 mph above treeline. Overnight, westerlies averaged 20 mph with gusts to 49mph. Any snow available for transport may just sublimate off the mountain, but isolated pockets could host new and perhaps some older wind slabs. Stability of older wind slabs is unknown. It is not out of the realm of possibility for a human triggered old wind slab. Remember, we had an "upside down" layered snowpack before our new snow last night. Additional weight of new snow/wind loading could stress underlying, older layers.
So, use your own observational skills to assess where old and new wind slabs might exist. Great topography for wind slabs include rock outcrops, narrow couloirs, ridgelines and the upper portions of bowls.This avalanche problem will be most prevalent above treeline. Wind slabs should be most suspect on slopes steeper than 37 degrees. Westerly winds will load mostly NE-E-SE slopes, but not limited to.
Near and below treeline, our warm temps, breakable crust and minimal accumulation amounts are not expected to cause problamatic avalanche related concerns for backcountry travelers today.
Forecast Discussion
The warm front that is passing through today and finally yielding to some cooler temperatures has wreaked some havoc on the snowpack.... mostly concerning ski quality. As for the avalanche danger, it's a bit of a mixed bag out there. Uncertainty exists for primarily the above treeline terrain as we have not been able to get any observations from ATL due to very poor visibility. Our old snow to new snow bonding went well with the first wave of the storm earlier this week (Wednesday/Thursday), bringing 15-20 cm new snow. Followed was our warm front and freezing rain that capped the snowpack with a breakable crust. Now we have about 3-6 inches of new snow overnight on top of it all. Again, above treeline is a wild card. Near and below treeline, the avalanche danger is going to be overall low due to warm temperatures and some rain on snow. As you gain elevation today, wind slabs and recent wind loading should be your primary focus. Skiing conditions are also a bit uncertain with the question, will the new snow be enough to support a skier on top of the horrendous breakable crust of yesterday?
The Castle Lake area received mostly rain on snow and expereinced several inches of settlement with the snowpack. Only the upper ramparts of Mt Eddy received a few inches of new snow. The best snowpack and most usable winter backcountry recreation is still on Mt Shasta.
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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
Some weather station trouble shooting yesterday brought us up into the lower Old Ski Bowl area. Above treeline terrain was pea soup and visibility was about 100 yards. Thus no new observations from above treeline terrain. That said, below and near treeline hosted a widespread and if I may say, gnarly breakable crust. Weather you were skiing, snowshoeing, extreme snow angeling, or snowmobiling, the snow conditions were not very good for any of those activities! This breakable crust was caused by our warm front that bulldozed over our cold front and brought rapid rising temps and some freezing rain to the snowpack, capping it off with a thick, 4F hard zipper crust, several centimeters thick. Now, about 3-6 inches of new snow sits on top of that crust this morning. Temperatures still remain warm this morning, 31 degree F at 7,500 to 8,000 feet on the mountain and about 35 degrees on the West side stations (Castle and Eddy). Temps will cool by this afternoon, but most precip will be finished, so little to no new snow expected today. Winds have averaged 20 mph with gusts to 49 on Gray Butte. High winds are expected for the entire weekend, 40-50+ mph, westerly.
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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
Temperatures have been slow to drop this weekend with snow levels fluctuating at around 6,500 feet. Cold air will in fact move in today lowering snow levels, however most of the precipitation with the recent system has passed through. Expect lingering snow and rain showers this morning followed by generally cloudy skies. Little to no new snow accumulation is expected for Saturday. The NWS Recreation forecast has issued an extreme wind warning for above treeline (ATL) terrain through Monday. Models certainly agree and one can expect steady westerly winds 40-50+ mph for the weekend, ATL. We are not cut loose from this wet period yet... No major precip is expected in the near future, but we may see the occasional lingering shower through the weekend and an overall unsettled and wet pattern for the next week or so.
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In Mt Shasta City at 0500, we have a current temperature of 42 F, with cloudy skies and light rain.
On Mt Shasta (South Side) in the last 24 hours...
Old Ski Bowl - 7,600 feet, the current temperature is 31 degrees F. Snow on the ground totals 47 inches with with 5-6 inches new snow and 1 inch settlement. Temperatures have ranged from 28F to 31F.
Gray Butte - 8,000 feet, the current temperature is 31 degrees F. Temperatures have ranged from 27 F to 31 F. Winds have averaged 20 mph out of the west/southwest with a gust to 49 mph..
Mt Eddy Range (West side of Interstate-5)...
Castle Lake - 5,600 feet, the current temperature is 36 degrees F. Temperatures have ranged from 32 F to 36 F. Snow on the ground totals 18 inches with no new snow and 5 inches of settlement due to rain on snow.
Mt Eddy - 6,500 feet, the current temperature is 33 degrees F. Temperatures have ranged from 30 F to 35 F. Snow on the ground measures 22 inches with little new snow and 1 inch of settlement. Winds have averaged 2 mph with gusts to 12 mph, southeast in nature.
THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 17.22 inches of water, normal is 9.45 inches, putting us at 182% of normal. For the month of December we received 0.75 inches of water, normal is 2.09 inches, putting us at 35% of normal, and finally... for the year of 2016 we've received 50.12 inches of water, normal is 37.45 inches, putting us at 133% 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: | 32 |
| Max. temperature in the last 24 hours: | 33 |
| Average wind direction during the last 24 hours: | West/Southwest |
| Average wind speed during the last 24 hours: | 10 mph mi/hr |
| Maximum wind gust in the last 24 hours: | 20 mph mi/hr |
| New snowfall in the last 24 hours: | 3-6 inches |
| Total snow depth: | 31 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 | Snow before 7am, then scattered snow showers, mainly between 7am and 10am. Temperature falling to around 27 by 5pm. Breezy. | Mostly cloudy. Blustery. | Mostly cloudy. Breezy. |
| Temperature (°F) | 27 | 20 | 28 |
| Wind (mi/hr) | Southwest 20-25 mph | West/Northwest 15-20 mph | Southwest 20-25 mph |
| Precipitation SWE / Snowfall (in) | / 0-1 | / 0 | / 0-.5 |
| For 9000 ft to 11000 ft | |||
| Saturday | Saturday Night | Sunday | |
| Weather | Snow before 7am, then scattered snow showers, mainly between 7am and 10am. Windy. | Mostly cloudy. Windy. | Mostly cloudy. Windy. |
| Temperature (°F) | 18 | 14 | 18 |
| Wind (mi/hr) | West 40-50 mph | West 1-3 | West 30-40 mph |
| Precipitation SWE / Snowfall (in) | / 1-3 | / 0 | / 0-.5 |
