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Avalanche Advisory for 2017-01-12 06:31:18

  • EXPIRED ON January 13, 2017 @ 6:31 am
    Published on January 12, 2017 @ 6:31 am
  • Issued by Nick Meyers - Shasta-Trinity National Forest

A lack in above treeline observations on Mt Shasta leaves uncertainty regarding wind slab stability. Blue skies will lure riders into the alpine. Old and newly formed wind slabs could be triggered by a skier or rider today. Expect MODERATE avalanche danger near and above treeline, all aspects. Below treeline, LOW danger will prevail. Proceed with caution above treeline. Do NOT let your guard down today.

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

Avalanche Problem 1: Wind Slab

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Wind slab stability is improving overall, especially below and near treeline. However,  due to poor visibility and access issues, we have a lack in above treeline observations on Mt Shasta. For this reason we have uncertainty regarding the sensitivity of wind slabs today. Visual observations have not revealed any natural avalanche activity, but snowpit analysis and targeted stability tests remain little. The January storm track brought feet of new snow and west/southwest winds to the mountain for many days on end. Following the storm, northwest winds have continued to transport snow on the mountain. Keep your feelers out for older and new wind slabs, all aspects, near and above treeline, especially on Mt Shasta and the upper ramparts of Mt Eddy. Slabs could be several feet thick and could break anywhere within the new snow or at the old snow/new snow interface. Any wind slab avalanches that occur would likely be fairly large in size. Natural avalanches are not expected, human triggered avalanches are possible. 

 

Avalanche Problem 2: Cornice

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Small to large cornices have been observed within the forecast area over the past several days. Two days ago, cornices were very sensitive to trigger. Cornices can often trigger avalanches on slopes below. Identify terra firm by observing rocks, twigs, trees and other signs of earth below your feet. If you find yourself tip-toeing out to the edge of a ridgeline/cornice to fulfill your inner daredevil, you may find yourself taking the elevator drop, becoming swept off your feet and down into undesireable terrain. Stand back!

Forecast Discussion

We can keep our heads above water for a few days. High pressure builds and the longest break in the storm action we've seen in a while ensues. We've taken the storm slab and most notable, persistent/deep slab problem off the advisory today. We continue to find less and less evidence of our 12/23 persistent weak layer as an avalanche problem. Snowpits in targeted areas show the persistent weak grains continuing to round and have become moist and non-reactive to stability tests due to ample amounts of rain exposure. Current avalanche concerns will likely exist on top of the 1/8 rain event crust. Near and above treeline terrain (>7,500 feet) is where lingering avalanche danger will exist, most notably wind slabs. We have limited observations from above treeline terrain. Sunny skies always lure folks up into the alpine. Use caution, ski and ride one at a time in avalanche terrrain, don't regroup in avalanche paths or run out zones, don't expose others to risk. Once again, do NOT let your guard down today.

Recent Observations

Observations were made in the Castle Lake area yesterday. During the tail end of the parade of storms that finally came to a close on 1/10, temperatures spiked as did the snow level which brought rain to upwards of 7,000 feet with wet effects on the snowpack to 7,500 to 8,000 feet. This was then followed by cooling temperatures which has now created a widespread crust on top of the snowpack for all aspects up to said elevations. This crust is supportable in some areas, breakable in others. Lingering snow flurries as of late has deposited some dust on crust, but otherwise the Castle Lake area skiing was pretty raunchy. Avalanche concerns in the Castle area are little. Rain runnels dominate a lot of lower elevation terrain. On Mt Shasta, viewed from afar, wind effect didn't appear to be to bad above treeline. Near treeline above 7,600 feet, softer snow with about 6-8 inches of snowmobile surface penetration was observed in a photo submission. We have not observed any avalanche activity or notable signs of instability since the end of our wild storm cycle, ending on 1/10. The snowpack has settled several inches in the last 24 hours, winds have died off and temperatures remain chilly. (See full Castle observation with photos below)



Old Ski Bowl, 1.11.17 - Photo: D Johnson

 

Weather and Current Conditions

Weather Summary

A cold pocket sweeps over California today which has made for a chilly morning over the forecast area. We have entered a period of high pressure that will provide the longest break in the parade of storms that we've seen in a while! A good problem to have as, if you are reading this, you are probably a backcountry enthusiast! Use this time to pick up the pieces, dry out, and prepare for the next round! Timing is uncertain now, however sometime on late Monday or Tuesday, another atmospheric river event is expected to impact the area with 7 day precipitation totals near flood warning criteria. Temperatures associated with the river event will begin warm. Cooler air pushes in mid week and will lower snow levels to more reasonable elevations. Naturally, more on this later. For today, a small chance for snow flurries this morning but otherwise expect nothing but blue skies shinning down on ya! Winds will be light. Enjoy and be safe!

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In Mt Shasta City at 0500, we have a current temperature of 28 F with a trace of new snow.

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

Old Ski Bowl - 7,600 feet, the current temperature is 13 degrees F.  Temperatures have ranged from 12 F to 21 F. Snow on the ground totals 118 inches with a trace of new snow and 3 inches of settlement

Grey Butte - 8,000 feet, the current temperature is 13 degrees F. Temperatures have ranged from 13 F to 22 F.  Winds have averaged 10-15 mph with gusts to 28 mph, blowing out of the west/northwest.

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

Castle Lake - 5,600 feet, the current temperature is 19 degrees F. Temperatures have ranged from 19 F to 30 F. Snow on the ground totals 58 inches with a trace of new snow and 2 inches of settlement.

Mt Eddy - 6,500 feet, the current temperature is 10 degrees F. Temperatures have ranged from 10 F to 24 F. Snow on the ground measures 65 inches with no new snow and 3 inches of settlement.  Winds have averaged 1-2 mph with gusts to 7 mph, blowing out of the southeast to southwest.

THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 28.27 inches of water, normal is 17.85 inches, putting us at 158% of normal.  For the month of January and for the year of 2017, we received 7.11 inches of water, normal is 2.64 inches, putting us at 269% 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: 24
Max. temperature in the last 24 hours: 26
Average wind direction during the last 24 hours: West/Northwest
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: trace inches
Total snow depth: 68 inches

Two Day Mountain Weather Forecast

Produced in partnership with the Medford NWS

For 7000 ft to 9000 ft
  Thursday
(4 a.m. to 10 p.m.)
Thursday Night
(10 p.m. to 4 a.m.)
Friday
(4 a.m. to 10 p.m.)
Weather A 30 percent chance of snow showers before 10am. Mostly sunny Mostly clear Sunny
Temperature (°F) 27 18 32
Wind (mi/hr) North/Northeast 0-5 mph North/Northeast 5-10 mph Northeast 5-10 mph
Precipitation SWE / Snowfall (in) / 0-.5 / 0 / 0
For 9000 ft to 11000 ft
  Thursday Thursday Night Friday
Weather A 30 percent chance of snow showers before 10am. Mostly sunny. Wind chill values as low as -9. Mostly clear. Wind chill values as low as -9. Blustery. Sunny. Wind chill values as low as -6. Blustery.
Temperature (°F) 11 11 24
Wind (mi/hr) East/Northeast 5-10 mph East/Northeast 0-.5 Northeast 20-25 mph
Precipitation SWE / Snowfall (in) / 0-.5 / 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.