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Avalanche Advisory for 2017-02-23 06:21:15

  • EXPIRED ON February 24, 2017 @ 6:21 am
    Published on February 23, 2017 @ 6:21 am
  • Issued by Nick Meyers - Shasta-Trinity National Forest

Avalanche danger is CONSIDERABLE above treeline for fresh wind slabs that have formed over the past 24-48 hours. Wind slabs could have the ability to step down into older layers. Avalanche danger is MODERATE near treeline and LOW below treeline. While likely not a serious threat, small loose wet avalanches are possible today with recent fresh snow and sunny skies, despite below freezing temperatures. 

 

Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential.

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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Concern today lies for fresh wind slabs that have formed over the past 24-48 hours. Use caution in leeward areas, near treeline and above treeline. Wind slabs can be found on primarily N-NE-E-SE slopes, but not limited to.  

 

 

Avalanche Problem 2: Cornice

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Small to large cornices have been observed in the forecast area. Some of these cornices, upon failure, have triggered wind slabs on slopes below. The chance of this occurring is becoming less so, but continue to keep this in mind as you are traveling along ridgelines or anywhere cornice formations are observed.

 

 

Avalanche Problem 3: Loose Wet

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Small, loose wet avalanches are possible today but not expected to be a serious problem for backcountry riders. New, light density snow with full sun could create some roller ball activity on sunny slopes below and near treeline.

Forecast Discussion

Remember, a blue sky is not our ticket to ride. Continue to pay attention in the backcountry and make safe terrain choices.

 

Recent Observations

Over the past 5 days, winds have blown primarily out of the west but with also some south, southwest and northwest forays. Recently, speeds of 15-20 mph with gusts into the 40mph range have been recorded. At 1800 hours yesterday, wind speeds died off considerably and have become mostly calm and variable. Temperatures remain cold. Five AM temps this morning are several degrees colder than yesterday at this time. A couple inches of new snow (1" - 4" / .21 SWE) fell in the last 24 hours in the mountains.

Snow stability continues to improve within the 3-4 feet of storm snow that fell over the past week. Recent observations made yesterday on the south side of Mt Shasta revealed no obvious signs of instability. Above treeline, scoured and wind effected snow surfaces were most prevalent. Ridgelines remain firm and some ridgelines on the west side of the forecast area are scoured down to rock. New, fresh wind slabs from recent winds is presenting the biggest hazard for backcountry riders. Obvious evidence of westerly and southerly winds were observed yesterday from cornice formations and visible blowing snow. Both Sun Bowl and Powder Bowl were actively being wind loaded with no tracks in them.

Weather and Current Conditions

Weather Summary

Cold temperatures are going to bring us into the weekend. A couple short stints of wintery weather will pass by late on Friday and Sunday into Monday. We are only expecting about .5 inches of water between the two storms, so nothing to write home about. Temperatures are going to stay chilly and thus snow levels will remain low, well below Mt Shasta City, probably in the 1,000 to 1,500 foot range. Winds for the next several days look very mellow, blowing light out of the north/northwest. Enjoy a little bit of sunshine, but expect a few inches of new snow in the coming days.

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

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

Old Ski Bowl - 7,600ft, the current temperture is 5 degrees F.  Temperatures have ranged from 5 F to 25 F.  Snow on the ground totals 194 inches with 2-4 inches of new snow and about 2 inches of settlement

Gray Butte - 8,000 feet, the current temperature is 10 degrees F. Temperatures have ranged from 10 F to 27 F.  Winds have averaged 15-20 mph/gust-42 mph out of the SSE until 1800 and then has decreased since then to 5 mph/gust-14 mph and variable.

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

Castle Lake - 5,800 feet, the current temperature is 15 degrees F. Temperatures have ranged from 15 F to 38 F. Snow on the ground totals 110 inches with 1-2 inches of new snow and 2 inches of settlement.

Mt Eddy - 6,500 feet, the current temperature is 13 degrees F. Temperatures have ranged from 13 F to 25 F. Snow on the ground measures 113 inches with 1-2 inches of new snow and 2 inches settlement. Winds have averaged 2 mph with gusts to 12 mph, blowing southeast.

THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 43.23 inches of water, normal is 27.87 inches, putting us at 155% of normal.  For the month of February, we have received 10.97 inches of water, normal is 5.60, which is 195% of normal. And finally for the year of 2017, we received 22.07 inches of water, normal is 12.66 inches, putting us at 174% 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: 10
Max. temperature in the last 24 hours: 28
Average wind direction during the last 24 hours: NW
Average wind speed during the last 24 hours: 5 mph mi/hr
Maximum wind gust in the last 24 hours: 10 mi/hr
New snowfall in the last 24 hours: 1-3 inches
Total snow depth: 122 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 Scattered snow showers before 10am. Mostly sunny. Chance of precipitation is 30%. Partly cloudy. A 30 percent chance of snow showers after 10am. Increasing clouds.
Temperature (°F) 23 11 22
Wind (mi/hr) Northwest 5-10 mph North 5-10 mph Southwest Calm, becoming 5-10mph in afternoon
Precipitation SWE / Snowfall (in) / 0-.5 / 0 / .5-1
For 9000 ft to 11000 ft
  Thursday Thursday Night Friday
Weather Scattered snow showers, mainly before 10am. Mostly sunny and cold. Wind chill values as low as -16. Chance of precipitation is 30%. Partly cloudy, with a low around -2. Wind chill values as low as -19. A 30 percent chance of snow showers after 10am. Increasing clouds and cold. Wind chill values as low as -21.
Temperature (°F) -1 -2 1
Wind (mi/hr) North/Northwest 5-10 mph West/Northwest 0-.5 West 5-10 mph
Precipitation SWE / Snowfall (in) / 0-.5 / 0 / .5-1

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.