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Avalanche Advisory for 2017-01-29 05:42:11
- EXPIRED ON January 30, 2017 @ 5:42 amPublished on January 29, 2017 @ 5:42 am
- Issued by Nick Meyers - Shasta-Trinity National Forest
Bottom Line
MODERATE avalanche danger continues above treeline, primarily in terrain above 10,000ft and on wind loaded slopes steeper than 35 degrees. LOW avalanche danger exists for all aspects near treeline and below treeline. Snow is available for transport, and fresh wind slabs may build today. With sunny skies and warm temperatures expected, be on the lookout for falling rime ice as well as possible wet loose snow surface instabilities.
Avalanche Problem 1: Wind Slab
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Likelihood ?CertainVery LikelyLikelyPossible
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With blowing snow visible above 10,000ft on Mt Shasta for the past several days, it is possible that new wind slabs could have formed in isolated areas. Redbanks, the Trinity Chutes, the east side gullies off of Sargents Ridge/Thumb Rock, and the Hotlum Headwall/Hotlum-Wintun are examples of areas where fresh deposits of wind loaded snow are most likely to exist. These locations are where steep slopes (>37 degrees) roll off the lower angle slopes of the upper mountain. These new, small to medium size wind slabs will be a concern for climbers and ski mountaineers who venture into upper elevation terrain. While these wind slabs may not produce large avalanches, a slide in any terrain where they do exist would likely have some undesireable consequences.
Forecast Discussion
The road (Everitt Memorial Hwy) to Bunny Flat (south side trailhead on Mt Shasta) and Castle Lake (west side trailhead) remain unplowed and closed at this time. Access to the backcountry can be made via the Mt Shasta Ski Park to the Gray Butte area or by parking at McBride Springs and heading up the road or Cascade Gulch. Snowmobile access will get you to many areas. The Pilgrim Creek and Deer Mountain snowmobile parks are open and trails are being groomed daily.
Soft snow conditions may lure backcountry travelers into complex avalanche terrain in upper elevations. Make sure to prioritize snow stability assessment today. Use visual observations to identify areas of loaded snow, and avoid slopes steeper than 35 degrees where evidence of the wind slab problem exists. With warm temperatures overnight and today, also be on the lookout for wet loose instabilities. If you are heading into the backcountry, always carry a beacon, shovel, and probe and know how to use them! As mentioned, access to the south side routes is limited to McBride Springs, approximately 4 miles up the Everitt Memorial Hwy. This means about 7 miles of snow covered roads OR an alternate route up Cascade Gulch toward Horse Camp.
Recent Observations
Yesterday, observations were made in the Eddy Range, Deadfall Lake area. At the snow survey site adjacent to the lake, an average of 60 to 70 inches of snow sits on the ground with snow/water equivalent coming in at an average of 65%. A temperature inversion is currently in place with the majority of the advisory area experiencing just a light freeze overnight, and warm temperatures this morning in the upper 30’s to low 40's at the majority of our remote weather stations. The most recent avalanche activity occurred within our last storm ending on January 23rd. Snowpack observations continue to reveal a deep, right side up, and strong snowpack. For several days in a row, stability tests have not identified any significant layers of concern, and they illustrate a low likelihood for layers within the snowpack to fracture under stress. Snowpack surfaces are variable, but a significant amount of unconsolidated, light snow exists. This allows for great skiing and riding in many places, but it also means plenty of snow is available for wind transport. Lately, winds have been light and variable near and below treeline. Lingering areas of loaded snow that formed during our most recent storm have been observed above treeline.
Weather and Current Conditions
Weather Summary
Temperature inversions are in effect this morning with Gray Butte and the Old Ski Bowl station clocking in at 41 F and 37 F degrees and Mt Shasta and Sand Flat at 23 F and 26 F degrees respectively. Virtually a carbon copy of yesterday will be had today. Winds will pick up a bit above treeline on the mountain and a few high clouds may filter through. We are still on track for a transition into unsettled weather this coming week, set to begin on Tuesday at some point.
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In Mt Shasta City at 0500, we have a current temperature of 23 F with clear skies.
On Mt Shasta (South Side) in the last 24 hours...
Old Ski Bowl - 7,600ft. the current temperature is 37 degrees F. Temperatures have ranged from 33 F to 47 F. Snow on the ground measures 146 inches with no new snow and 2 inches of settlement.
Grey Butte - 8,000 feet, the current temperature is 41 degrees F. Temperatures have ranged from 38 F to 48 F. Winds have averaged 5-10 mph with gusts to 21 mph, easterly until midnight and then switched to west/northwest.
Mt Eddy Range (West side of Interstate-5)...
Castle Lake - 5,600 feet, the current temperature is 37 degrees F. Temperatures have ranged from 35 F to 48 F. Snow on the ground totals 95 inches with no new snow and 2 inches of settlement.
Mt Eddy - 6,500 feet, the current temperature is 33 degrees F. Temperatures have ranged from 29 F to 50 F. Snow on the ground measures 80 inches with no new snow and 2 inches of settlement. Winds have averaged 1-5 mph with gusts to 7 mph, blowing west/southwest.
THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 32.26 inches of water, normal is 21.64 inches, putting us at 149% of normal. For the month of January and for the year of 2017, we received 11.10 inches of water, normal is 6.43 inches, putting us at 172% 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: | 26 |
| Max. temperature in the last 24 hours: | 36 |
| Average wind direction during the last 24 hours: | Easterly, then west/northwest |
| Average wind speed during the last 24 hours: | 0-5 mi/hr |
| Maximum wind gust in the last 24 hours: | 10 mi/hr |
| New snowfall in the last 24 hours: | 0 inches |
| Total snow depth: | 94 inches |
Two Day Mountain Weather Forecast
Produced in partnership with the Medford NWS
| For 7000 ft to 9000 ft | |||
|---|---|---|---|
|
Sunday (4 a.m. to 10 p.m.) |
Sunday Night (10 p.m. to 4 a.m.) |
Monday (4 a.m. to 10 p.m.) |
|
| Weather | Mostly sunny | Partly cloudy | Mostly sunny |
| Temperature (°F) | 47 | 32 | 48 |
| Wind (mi/hr) | Southeast, becoming northeast/east in the morning hours 0-5 mph | Northeast 0-5 mph | Southeast 0-5 mph |
| Precipitation SWE / Snowfall (in) | / 0 | / 0 | / 0 |
| For 9000 ft to 11000 ft | |||
| Sunday | Sunday Night | Monday | |
| Weather | Mostly sunny. Breezy. | Mostly cloudy. Windy. | Mostly sunny. Windy. |
| Temperature (°F) | 33 | 31 | 33 |
| Wind (mi/hr) | West 10-15 mph | West 0 | West 20-30 mph |
| Precipitation SWE / Snowfall (in) | / 0 | / 0 | / 0 |
