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Avalanche Advisory for 2016-01-04 07:01:00
- EXPIRED ON January 5, 2016 @ 7:01 amPublished on January 4, 2016 @ 7:01 am
- Issued by Nick Meyers - Shasta-Trinity National Forest
Bottom Line
Overall, LOW avalanche danger will exist on all aspects and elevations today. While avalanches remain unlikely, some unstable snow could exist on isolated, steep terrain features.
Expect rising avalanche danger over the next 48 hours due to rapid accumulation of new snow, high southerly winds and areas of existing surface hoar creating wind, storm and persistent weak layer avalanche problems.
Avalanche Problem 1: Normal Caution
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Wind slabs still do exist in isolated areas in the forecast area, mostly near and above treeline. Some cornices still linger over previously wind loaded slopes as well so give them space! Continue to practice normal caution and safe travel techniques.
The avalanche danger will increase tonight with the significant amount of rapid, new snow expected in the weather forecast. Areas that have preserved and subsequently buried surface hoar should be highly suspect for direct action, storm slab avalanches. These potential avalanches will be most reactive near the end of the storm as new storm snow and wind deposited snow gains depth and adds stress to the snowpack. Snow does not like rapid change!
Normally, sun or wind will destroy surface hoar pretty easily. However- steep, cold, north facing slopes below and near treeline will be the best areas for preserved and buried surface hoar creating a weak layer below new snow. Tomorrow, it's certain the avalanche danger will rise for wind and storm slab avalanches and we could see another round of the persistent weak layer avalanche problem.
"Normal Caution" refers to safe travel practices that should be exercised during every tour, which include:
-Expose only one person at a time to avalanche terrain, both skinning up AND riding down.
-Avoid areas with possibly unstable snow.
-Travel from one safe zone to another crossing avalanche paths one at a time, and avoiding terrain traps. Is your "safe zone" really safe if a slide were to occur?
-Communicate clearly and often with your travel partners. Don't be afraid to speak up if you notice poor decision making or any "red flags".
Forecast Discussion
Winter storm warning in effect... Our favorite 5 words! Northern California sets up for a fast moving albeit potent storm to arrive late today/tonight. Clouds will increase throughout the day. Moderate to heavy snowfall will occur tonight and Tuesday morning with snow levels at 3,500 to 4,000 feet. Precipitation forecasts show about .75 inches of water over a 12 hour period beginning 4pm today, which will mean 8-10 inches of snow in the forecast area by tomorrow morning. We will see southerly winds, 10-15 mph below treeline and 30-40 mph near and above treeline.
THIS SEASON PRECIPITATION: Since October 1st (the wet season), we have received 9.49 inches of water, normal is 15.92 inches, putting us at 59% of normal. For the month of January, we have received 0.00 inches of water, normal is 0.71 inches, putting us at 0% of normal. For the year of 2016 we've received 0.00 inches of water, normal is 0.71 inches, putting us at 0% of normal
Recent Observations
Widespread development of surface hoar in protected areas mainly at and below treeline, while not an issue today, could become an issue tomorrow. Surface hoar has been observed on the snow around Bunny Flat, as well as on the Trinity Divide near Parks Creek summit. Surface hoar is fun to look at, take pictures of, eat and ski through but could be a problematic weak layer in our near future. Observations made on 1.2.16 on a northerly facing aspect near Parks Creek summit revealed surface hoar development of 2-5cm thick! A good chance exists for surface hoar crystals to maintain shape and structure on NW-N-NE facing slopes below and near treeline. A recipe for an avalanche is setting up for the next few days: Rapid onset of new snow over a short period of time, pockets of existing surface hoar, south winds blowing 30-40 mph near and above treeline. These factors will present storm and wind slab avalanche problems as well as perhaps another persistent weak layer problem.
For today the avalanche danger is LOW. Normal caution is advised. Existing wind slabs still do exist in the forecast area with direct evidence from the photo below. While likely small, they still could certainly be enough to sweep a rider into undesireable terrain.
Safe travel techniques should be followed. Only expose one person at a time to avalanche terrain, regroup in "safe" spots out of avalanche paths, avoid terrain traps, and have open communication with in your group. LOW avalanche danger is not the green light for complacency. Unstable snow on isolated terrain features could still result in an avalanche that could injure, bury, or kill someone.
Human triggered wind slab above Durney Lake in the Mt Eddy Range, 1/1/16. Total snow depth: 180cm. Visible wind loading in area. Crown - 30 cm at deepest. Aspect unknown though appears to be northerly. Photo: O. Stroud
Surface hoar development on snow along ridge near Parks Cr. summit, north of Mt. Eddy. Preserved surface hoar like this, in the Eddies and other zones in the forecast area, will be buried by new snow and could present our next weak layer for storm and wind slab avalanches. 1/2/2016 - Photo: Jon Dove
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The Sand Flat cross country ski trails are in great shape and ready for your cross country skis or snow shoes. These are backcountry trails 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. Thank you, and enjoy!
The Pilgrim Creek Snowmobile Park is open! Trails are being groomed currently. Head to our "Education" tab on our website and find the snowmobile section for trail information, grooming status and other sledder resources!
The Five Red Flags of Avalanche Danger any time of year include: 1) Recent/current avalanche activity 2) Whumpfing 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 36 F, two degrees warmer than yesterday at this time, with mostly cloudy skies and calm winds.
MOUNTAIN WEATHER STATION INFORMATION (0500hrs):
On Mt Shasta (South Side) in the last 24 hours...
Old Ski Bowl - 7,600 feet, the current temperature is 27 degrees F. Snow on the ground totals 51 inches with 1 inch settlement. Temperatures have ranged from 21 F to 30 F.
Grey Butte - 8,000 feet, the current temperature is 25 degrees F. Temperatures have ranged from 18 F to 28 F. Winds have been averaging 12 mph and southerly in direction, with a max gust to 35 mph out of the SSW.
Mt Eddy Range (West side of Interstate-5)...
Castle Lake - 5,600 feet, the current temperature is 31 degrees F. Temperatures have ranged from 25 F to 36 F. Snow on the ground measures 30 inches with little settlement.
Mt Eddy - 6,500 feet, the current temperature is 29 degrees F. Temperatures have ranged from 24 F to 31 F. Snow on the ground measures 43 inches with no new snow and little settlement. Winds have averaged 2 mph SSW in direction, with a max gust to 15 mph, SSW.
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: | 30 |
| Max. temperature in the last 24 hours: | 32 |
| Average wind direction during the last 24 hours: | Southerly |
| Average wind speed during the last 24 hours: | 5-10 mi/hr |
| Maximum wind gust in the last 24 hours: | 35 mi/hr |
| New snowfall in the last 24 hours: | 0 inches |
| Total snow depth: | 51 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, mainly after 10am | Snow, rising temperatures | Snow |
| Temperature (°F) | 30 | 25 | 31 |
| Wind (mi/hr) | South/southeast 5-10 mph | South/southeast 10-15 mph | South 10-15 mph |
| Precipitation SWE / Snowfall (in) | / 1-2 | / 5-7 | / 2-4 |
| For 9000 ft to 11000 ft | |||
| Monday | Monday Night | Tuesday | |
| Weather | Snow, mainly after 10am, windy | Snow, windy | Snow likely before 10 pm, then snow showers |
| Temperature (°F) | 20 | 18 | 15 |
| Wind (mi/hr) | South 30-40 mph | South 2-4 | Southwest 40-50 mph |
| Precipitation SWE / Snowfall (in) | / 2-4 | / 6-8 | / 4-6 |
