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Avalanche Advisory for 2016-02-05 06:51:49
- EXPIRED ON February 6, 2016 @ 6:51 amPublished on February 5, 2016 @ 6:51 am
- Issued by Jon Dove - Shasta-Trinity National Forest
Bottom Line
Overall, LOW avalanche danger exists at all elevations, all aspects. Pockets of MODERATE avalanche danger remain above treeline for lingering wind slabs on S-SE-E-NE-N-NW aspects. Isolated areas of unstable snow may be found on protected terrain features around rock outcroppings, near ridge tops, on slopes 37 degrees and steeper. Loose wet snow instabilities will become an increasing risk on sun exposed aspects. Evaluate snow and terrain carefully. Normal caution is advised.
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
Remaining wind slabs of small to possibly medium in size will be found on leeward S-SE-E-NE-N-NW aspects near and above treeline in protected areas around rock outcroppings, just below ridge tops. Several pockets of wind slab formations were observed yesterday all along Casaval Ridge at the top of the SE aspect that drops into Avalanche Gulch. An extended column stability test performed yesterday at 10,500 feet in Avalanche Gulch showed the wind slab at that location stubborn to trigger. If just the right trigger point is stumbled upon, however, the resulting slide could entrain enough snow to easily bury, injure, or even kill a person. The most likely place to find and trigger a wind slab today will be near and above treeline on leeward NW-N-NE-E-SE-S aspects on slopes 37 degrees and steeper, in complex terrain, steep chutes, convexities/roll overs, and cross loaded depressions. Sensitivity to trigger of wind slabs in these areas is not known, so best to avoid them all together.
Avalanche Problem 2: Loose Wet
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Character ?
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Aspect/Elevation ?
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Likelihood ?CertainVery LikelyLikelyPossible
Unlikely
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Size ?HistoricVery LargeLargeSmall
Sunshine and warming temperatures will increase the risk of loose wet snow instabilities over the next few days. Roller balls, pin wheels, and point release wet slides will be the most present loose wet instabilities. They will be found primarily on, but not limited to, southerly facing aspects below, near, and above treeline. While typically not a huge danger these types of slides could easily knock a person off of their feet and push them into a terrain trap, over a cliff band, or into other undesirable terrain. They could even entrain enough snow to bury a person. Loose wet snow slides will become more common in the coming days.
Forecast Discussion
Yesterday was a perfect example of what to expect for the first half of the coming week as we transition to a relatively calm and dry weather pattern. The current long wave ridge now over the area will break to the east later in the morning allowing the next long wave trough and the associated cold front to move in. The trough, however, will weaken as it moves ashore with the majority of energy focused to the north of our area. Forecasts call for a slight chance of precipitation late this afternoon into tonight, but when you take a look at the "quantitative precipitation forecast" our area is predicted to receive 0.00 inches of water. If any rain or snow does fall, it will be extremely light. Strong upper level ridging will begin to build again late tonight into Saturday morning as the trough moves out to the east heralding in sunshine and warming temperatures. The ridge of high pressure will move very slowly eastward, amplifying through Monday. There will be no threat of inclement weather until later in the week with the next of a series of short wave troughs arriving sometime on Thursday.
THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 22.62 inches of water, normal is 23.24 inches, putting us at 97% of normal. For the month of February we've received 0.13 inches of water, normal is 0.97 inches, putting us at 13% of normal, and for the year of 2016 we've received 13.13 inches of water, normal is 8.03 inches, putting us at 163% of normal .
Recent Observations
Due to the improving weather (depending on your perspective) with dry, sunny conditions forecast for our area over the weekend I decided a look at snowpack conditions at higher elevations would be prudent. A ski tour up Avalanche Gulch to Helen Lake revealed a variety of snow conditions above treeline. In a word, the snow was variable. Moderate to strong westerly winds during the first half of the week have scoured some areas down to a firm, icy crust. Scattered about are wind sculpted pillows and scales, wind buff powder snow in depressions and gullies, rime covered rocks at high elevation (11,000 ft and above), and wind slabs in protected areas around rock outcroppings just below ridge tops. Casaval Ridge in particular has numerous small to medium sized wind slab formations along it's serrated top. The crown of a recent wind slab avalanche (see photo below) was seen from my perch at Helen Lake on an ESE facing aspect, in a protected pocket along the top of Green Butte Ridge that drops into Old Ski Bowl. It is not known when the slide occurred, however, it is a perfect example of our current avalanche problem.
A full snow study pit was dug just above Helen Lake at 10,500 ft. on a SW facing slope with a 23 degree angle at the top of Avalanche Gulch proper. An extended column test was performed resulting in a score of ECTX. The slope angle was too low to truly glean any concrete beta in regards to bonding of wind slabs with underlying snow at that location. From what I found, wind slabs may be stubborn to trigger. When you increase the slope angle to 37-45 degrees, where most suspect wind slabs exist, their sensitivity to disturbance is unknown.
Climbing conditions appear to be pretty good for this time of year. Casaval, or one of the other ridge routes, would be a good option this weekend. Avalanche Gulch climbing conditions are good with relatively firm snow for decent boot packing. Boot penetration of just 5 cm was recorded at Helen Lake. That being said, the variable snow conditions will present a variety of surfaces to travel over. Some post holing is possible at higher elevations in wind protected areas. If making a climb this weekend ascend the moraines staying out of terrain traps such as "climber's gully" or Avalanche Gulch proper. In making a ski/board descent off of or climbing up Casaval, Green Butte, or Sargents Ridge use caution around, or avoid all together wind loaded pockets just below the ridge top in protected areas around rock outcrops. For today, evaluate snow and terrain carefully above treeline for any signs of wind loading on leeward S-SE-E-NE-N-NW aspects. Decent visibility above treeline will surely lure folks to higher elevations onto open slopes requiring more objective decision making. Isolated terrain, on open slopes 37 degrees and steeper, the tops of chutes and couloirs, near rock outcroppings, depressions, and along roll overs/convexities will be the places that one would be the most likely to find and potentially trigger a wind slab avalanche. For those traveling in the backcountry today normal caution is advised. Don't let complacency cloud your observation of snowpack and terrain as you make your way up in elevation. Maintain good group communication, stay spaced out when crossing known avalanche paths or suspect slopes, identify features of concern, and avoid them.
Full snow pit profile at high elevation location near Helen Lake, top of Avalanche Gulch proper, Mt Shasta: Jon Dove
Wind effected snow conditions at upper 50/50 Flat, approximately 9,800 ft. elevation, Mt. Shasta-photo: Jon Dove
Crown of recent wind slab avalanche on an isolated aspect, Easterly facing protected pocket along the Green Butte Ridge top in Old Ski Bowl-photo: Jon Dove
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LOCAL AREA ROAD, NORDIC and SNOWMOBILE PARK STATUS:
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. 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 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 Castle Lake road is plowed to the lake. The Everett Memorial Highway is plowed to Bunny Flat.
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 27 F, three degrees cooler than yesterday at this time. Skies are clear with calm winds.
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 121 inches with no new snow and 1 inch of settlement. Temperatures have ranged from 19 F to 37 F.
Grey Butte - 8,000 feet, the current temperature is 28 degrees F. Temperatures have ranged from 18 F to 35 F. Winds have been averaging 0-5 mph then increasing to 25-30 mph, with a max gust to 35 mph, east.
Mt Eddy Range (West side of Interstate-5)...
Castle Lake - 5,600 feet, the current temperature is 32 degrees. Temperatures have ranged from 22 F to 41 F. Snow on the ground totals 65 inches with no new snow and 1 inch of settlement.
Mt Eddy - 6,500 feet, the current temperature is 26 degrees F. Temperatures have ranged from 20 F to 35 F. Snow on the ground measures 84 inches with no new snow and 1 inch of settlement. Winds have averaged 3 mph, variable in direction with a max gust of 8 mph, east/southeast.
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: | 23 |
| Max. temperature in the last 24 hours: | 34 |
| Average wind direction during the last 24 hours: | Variable |
| Average wind speed during the last 24 hours: | 0-5 increasing to 25-30 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: | 98 inches |
Two Day Mountain Weather Forecast
Produced in partnership with the Medford NWS
| For 7000 ft to 9000 ft | |||
|---|---|---|---|
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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 | Partly sunny with a 30% chance of snow after 4 pm. | Mostly cloudy. A chance of snow before 10 pm, then a slight chance of snow showers after 10 pm. | Mostly sunny. |
| Temperature (°F) | 38 | 26 | 40 |
| Wind (mi/hr) | Southwest 25-30 mph | Southwest 15-20 mph | Variable 5-10 mph |
| Precipitation SWE / Snowfall (in) | / 0-.5 | / 0-.5 | / 0 |
| For 9000 ft to 11000 ft | |||
| Friday | Friday Night | Saturday | |
| Weather | Partly sunny with a 30% chance of snow after 4 pm. Windy | Mostly cloudy. A chance of snow before 10 pm, then a slight chance of snow showers after 10 pm. Windy | Mostly sunny. Windy |
| Temperature (°F) | 25 | 24 | 26 |
| Wind (mi/hr) | Southwest 15-20 mph increasing to 35-40 mph in the afternoon with higher gusts possible. | West 0-.5 | West 15-20 mph with higher gusts. |
| Precipitation SWE / Snowfall (in) | / 0-.5 | / 0-.5 | / 0 |
