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Avalanche Advisory for 2017-02-12 06:16:53

  • EXPIRED ON February 13, 2017 @ 6:16 am
    Published on February 12, 2017 @ 6:16 am
  • Issued by Nick Meyers - Shasta-Trinity National Forest

New wind slabs on primarily SW-W-NW facing aspects above 8500ft pose the greatest avalanche concern today. Expect overall MODERATE avalanche danger above treeline. Small, human triggered avalanches are possible on newly wind loaded slopes 35 degrees and steeper.  Natural avalanches are unlikely.  The avalanche danger is LOW near treeline and below treeline. Roller balls and loose-wet style instabilities are also possible today on southerly, lower elevation slopes but not expected to pose a serious threat to backcountry riders.

 


 

Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.

Avalanche Problem 1: Wind Slab

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Winds have shifted and averaged 20 mph with gusts into the 30's out of the east over the past 24 hours. Yesterday, visible blowing snow was observed. With snow available for transport, new wind slabs will be possible above treeline.  These new wind slabs should be small and not extend very far from ridgelines, near the tops of bowls, couloirs and/or rocky outcroppings. Old wind slabs formed early in the week are very stubborn to trigger. Signs of recent wind loading including cornices, blowing snow, wind drifts, wind pillows and wind created textures on the snowpack. Use this information to avoid possible wind slabs.

 

Avalanche Problem 2: Loose Wet

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Loose-wet activity is possible today involving only the top, softer snow layers of the snowpack. Skier induced roller balls were easily triggered on sunny slopes below 8,500 feet on Mt Shasta yesterday. Any loose-wet activity today will be likely small and inconsequential to backcountry riders, however, on occasion a loose-wet slide can sweep a rider off their feet and into undesirable terrain.

Forecast Discussion

Nothing but blue skies shining down on us today. Very good stability exists below and near treeline due to heavy rain on snow followed by cooling temperatures. Above treeline, use caution in regards to the potential for any newly formed, small wind slabs from the moderate easterly winds over the past 24 hours. Overall, variable skiing and riding conditions exist.

Join us today at Mount 'A' up near Ashland, OR at 9:00am for Companion Rescue, Mt Ashland Beacon Park.

Recent Observations

Observations yesterday in Avalanche Gulch, Casaval Ridge and Giddy Giddy Gulch found 2-4cm of new snow on top of variable mostly firm snow surfaces. All these locations area access via the Bunny Flat trailhead, south side of Mt Shasta. The Everitt Memorial Highway has re-opened, the road is in good shape and the trailhead fully functioning. Large rain runnels exist up to about 8,500 feet. Runnels begin to taper to smoother snow surfaces above this elevation. On steeper southerly facing slopes above 9,000, very firm and icy snow was consistently found. For climbers and ski mountaineers, a long slide for life is certainly possible with conditions as such. Crampons and an ice axe are strongly advised. Solar radiation influence was significant, specifically its affect on the rime ice. Mt Shasta is plastered in snow and rime currently and any daytime warming will loosen and cause small to large chunks of rime ice to fall onto slopes below! Be careful and wear a helmet. Ski penetration was consistent at 2-4cm for most of the day. A few ski turns below 8,500 feet on sunny aspects steeper than 35 degrees produced roller balls, though not enought to pose threat to bakcountry riders. No recent avalanches or significant signs of instability were observed yesterday. Winds have been variable, however, have organized over the last 24 hours to primarily east. 

Weather and Current Conditions

Weather Summary

A strong ridge of high pressure remains aloft and there is little change in the weather today. This setup will keep any precipitous event from hitting the area until next week. Some valley fog and inversions are in place this morning and can be expected tomorrow. A few high clouds might be seen today, but otherwise mostly blue should come into view for those keeping thier heads up, as one should try always! Clouds will become more widespread at the beginning of next week.  Models suggest the onset of more precipitation on Tuesday night. Enjoy the day!

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In Mt Shasta City at 0500, we have a current temperature of 24 F with mostly clear skies.

On Mt Shasta (South Side) in the last 24 hours...

Old Ski Bowl - 7,600ft. the current temperture is 31 degrees F.  Temperatures have ranged from 17 F to 34 F.  Snow on the ground totals 160 inches with no new snow and 3 inches of settlement.

Grey Butte - 8,000 feet, the current temperature is 34 degrees F. Temperatures have ranged from 19 F to 34 F.  Winds have averaged 20 mph with gusts to 42 mph, blowing primarily out of the east.

Mt Eddy Range (West side of Interstate-5)... 

Castle Lake - 5,800 feet, the current temperature is 28 degrees F. Temperatures have ranged from 20 F to 34 F. Snow on the ground totals 84 inches with no new snow and 2 inches of settlement.

Mt Eddy - 6,500 feet, the current temperature is 26 degrees F. Temperatures have ranged from 21 F to 35 F. Snow on the ground measures 81 inches with no new snow and 1 inch of settlement. Winds have averaged 1-3 mph with gusts to 10 mph, blowing south/southwest.

THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 39.04 inches of water, normal is 24.93 inches, putting us at 156% of normal.  For the month of February, we have received 6.78 inches of water, normal is 2.66, which is 254% of normal. And finally for the year of 2017, we received 17.88 inches of water, normal is 9.72 inches, putting us at 183% 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.

CURRENT CONDITIONS at Bunny Flat (6950 ft)
0600 temperature: 22
Max. temperature in the last 24 hours: 36
Average wind direction during the last 24 hours: East
Average wind speed during the last 24 hours: 5-10 mi/hr
Maximum wind gust in the last 24 hours: 15 mi/hr
New snowfall in the last 24 hours: 0 inches
Total snow depth: 95 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 Sunny Mostly clear Mostly sunny
Temperature (°F) 47 29 50
Wind (mi/hr) East/Northeast 0-5 mph East 0-5 mph East 0-5 mph
Precipitation SWE / Snowfall (in) / 0 / 0 / 0
For 9000 ft to 11000 ft
  Sunday Sunday Night Monday
Weather Sunny Mostly clear Mostly sunny
Temperature (°F) 32 31 31
Wind (mi/hr) North 5-10 mph North, becomings south after midnight 0 Southeast 5-10 mph, becoming 0-5 mph
Precipitation SWE / Snowfall (in) / 0 / 0 / 0

Disclaimer

This advisory does not apply to Ski Areas or Highways and is for the Mt. Shasta, Castle Lake and Mt. Eddy backcountry. Use this information for guidance only. You may find different conditions in the backcountry and should travel accordingly. This advisory expires on midnight of the date it was posted unless otherwise noted.