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Avalanche Advisory for 2017-01-15 06:02:36

  • EXPIRED ON January 16, 2017 @ 6:02 am
    Published on January 15, 2017 @ 6:02 am
  • Issued by Nick Meyers - Shasta-Trinity National Forest

MODERATE avalanche danger continues above treeline on all aspects above 10,000 feet.  LOW avalanche danger exists near and below treeline.  Wind slabs and cornices are the avalanche problems for the day.  Triggering stubborn wind slabs/cornices remains possible. This is a low likelihood, high consequence situtation. Winds slabs/cornices have been very stubborn to trigger, but if set loose, a large and devastating avalanche could occur. Evaluate snow and terrain carefully and identify features of concern.

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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Wind slabs remain the primary avalanche concern and have the potential to exist on all aspects near treeline and above treeline.  Human triggered wind slab avalanches are possible, and naturally triggered wind slabs are unlikely.  Wind slabs that formed during our most recent storm are now hard slabs that are several feet thick.  These lingering wind slabs pose a low likelihood, high consequence scenario for backcountry travelers, especially in upper elevation terrain.  It has been very difficult to trigger an old wind slab, but if a wind slab avalanche does occur, it would likely be large and dangerous.  Practice good travel techniques, and only expose one skier or rider at a time to avalanche terrain.  Regroup in islands of safety, and be aware of what is above you and below you.  Use visual observations to identify the wind slab problem.

Avalanche Problem 2: Cornice

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Cornices formed during our most recent storm event, and exist on ridgelines and exposed terrain features near and above treeline on all aspects.  Cornices are dangerous snow formations that are often overhung, and can break in very unpredictable ways.  Today, a falling cornice also has the potential to trigger a wind slab on slopes below.  Be sure to stand back, and give overhung cornices plenty of space.  Evaluate slopes that are threated by cornices from above, and watch for warming temperatures and solar radiation input throughout the day to increase the likelihood of cornice failure.  

Forecast Discussion

It has been 5 days since our advisory area has received any precipitation, and clear and sunny weather will continue for now.  Overall, our snowpack has adjusted well to the added weight of the recent storms, and stability has been good.  Elevations 6000ft and below likely hold a stout, breakable crust, and evidence of the 01/08 rain on snow event is widespread.  Above this elevation, cold powder snow exists, providing very good skiing and riding conditions. Southerly aspects may have a funky sun crust on them today. Upper elevation (>10,000 feet) terrain holds the greatest potential for avalanches.  Today, snowpack assessment should target the wind slab and cornice problems. Isolated loose wet instabilities are possible on lower elevation terrain, southerly aspect near and below treeline. This problem is not expected to cause trouble for backcountry users.

Recent Observations

Yesterday brought a classic, sunny Northern California day to the area. Light and variable winds and a wide open blue sky hosted a nice crowd of folks up on the south side of the big hill. Aside from the Castle Lake area, great skiing above 6,000 feet has been the overall report from riders and gliders and we would concur. Temperatures yesterday were the warmest we've seen since the end of the Janurary storm cycle. Highs in the upper 30's to low 40's were recorded across the area. Roller balls were observed in the afternoon hours on SE-S-SW facing slopes below and near treeline. None of these loose snow observations posed a threat to backcountry enthusiasts. Temperatures today are expected to be near the same. With the sun warming those southerly slopes, we are guessing that those same slopes will now have perhaps a thin frozen sun crust on them today. It may soften by the afternoon, it may not. Colder, northerly facing slopes will host the best persisting powder. We continue to see no recent avalanches and/or significant signs of instability. 

 

Weather and Current Conditions

Weather Summary

If you've missed out on the clear, crisp and sunny days of late, you're in luck. Another day of great winter weather is coming at you on this fine MLK weekend. We're seeing slight inversions this morning. Air stagnation warnings have gone out for much of Southern Oregon. We may see the similar stagnation going on locally with some fog and low lying air pollution. This should clear out as the day progresses, winds will be light and variable and blue sky will dominate overhead. A few lingering clouds this morning should not cause worry; they should clear with the day also.

Models continue to push back the arrival of the atmospheric river event we've been talking about. Currently were expecting things to get going on Tuesday. This storm system will not be nearly as potent as the last, but will certainly provide inches of rain and unfortunately high snow levels (7-8k feet) with the heaviest precip for about a 12-18 hour period. Temperaturs will drop Wednesday, to little to late to bring any significant low elevation snow. Friday however, another nice looking storm is showing up in models and this one could bring snow down to 3500 feet. So, get your sun fix now, a wet week is in store.

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In Mt Shasta City at 0500, we have a current temperature of 27 F with clear skies.

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

Old Ski Bowl - 7,600 feet, the current temperature is 30 degrees F.  Temperatures have ranged from 26 F to 40 F. Snow on the ground totals 112 inches with a no new snow and 2 inches of settlement

Grey Butte - 8,000 feet, the current temperature is 33 degrees F. Temperatures have ranged from 31 F to 39 F.  Winds have averaged 20 mph out of the east/northeast until 1000 and then shut off, averaging 1-5 mph, variable in direction.

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

Castle Lake - 5,600 feet, the current temperature is 24 degrees F. Temperatures have ranged from 22 F to 32 F. Snow on the ground totals 54 inches with no new snow and 1 inch of settlement.

Mt Eddy - 6,500 feet, the current temperature is 33 degrees F. Temperatures have ranged from 22 F to 39 F. Snow on the ground measures 60 inches with no new snow and 2 inches of settlement.  Winds have averaged 2-4 mph with gusts to 7 mph, blowing out of the west/southwest.

THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 28.27 inches of water, normal is 18.58 inches, putting us at 152% of normal.  For the month of January and for the year of 2017, we received 7.11 inches of water, normal is 3.37 inches, putting us at 210% 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: 21
Max. temperature in the last 24 hours: 33
Average wind direction during the last 24 hours: Variable
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: 64 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 Mostly clear Mostly sunny
Temperature (°F) 40 24 48
Wind (mi/hr) Northeast 5-10 Northeast 5-10 North/Northeast 5-10 mph
Precipitation SWE / Snowfall (in) / 0 / 0 / 0
For 9000 ft to 11000 ft
  Sunday Sunday Night Monday
Weather Mostly sunny. Breezy. Mostly clear. Windy. Mostly sunny. Breezy.
Temperature (°F) 31 31 33
Wind (mi/hr) North 10-15 mph North/Northeast 0 North/Northeast becoming west/northwest in the afternoon. 15-20 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.