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Avalanche Advisory for 2017-03-01 06:20:24

  • EXPIRED ON March 2, 2017 @ 6:20 am
    Published on March 1, 2017 @ 6:20 am
  • Issued by Nick Meyers - Shasta-Trinity National Forest

MODERATE avalanche danger will exist near treeline and above treeline today due to the wind slab avalanche problem. Northwest winds have contributed to wind loading on primarily S-SE-E aspects, but not limited to. Human triggered wind slabs near ridgelines and tops of bowls are possible.
Below treeline, avalanche danger is LOW. 

 

 

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 slabs remain on ongoing concern in near treeline and above treeline terrain. Northwest winds have died off this morning however previous drifting snow over the past several days has contributed to widespread wind loading, especially on Mt Shasta. Unstable wind slabs will still lurk and could be human triggered today. Be able to identify areas of wind drifted snow and avoid these areas.

 

Forecast Discussion

A virtual firehose of wind deposit was observed on Mt Shasta yesterday. While winds have died off, wind slabs sit perched atop many classic starting zones on Mt Shasta and elsewhere within the forecast area. Warming temps will aid in stabilizing our snowpack, but today is the transition day and wind slabs could remain touchy. Think twice before committing to any wind loaded slope steeper than 30 degrees. 

Recent Observations

Yesterday yielded a gorgeous day with mostly clear skies. Temperatures have been creeping upward this week with daytime highs several degrees warmer each day. Our light density powder snow that everyone has been enjoying is beginning to fade. Many aspects below 8,000 feet will now have a zipper crust of sort from yesterdays warm February sun. Shaded and/or northerly aspects will likely still hold some nice powder snow. Moderate to strong northwest winds have been prevailing and blowing snow was visible from town on Mt Shasta yesterday morning. Rapid wind loading was obvious and proof was in the pudding: almost the entire slope of Sun Bowl slid sometime in the AM hours yesterday.  (see observation for photos) We believe this was a natural avalanche and may have been triggered by a cornice failure. There was an unconfirmed report that a portion of Powder Bowl (next bowl over to the east) may have slid as well. On the west side in the Eddy Range, winds were much less and no recent signs of avalanches or avalanche danger were observed. Some small cornices were noted, along with scouring on ridgelines. Overall, soft snow could be found in most areas with boot penetration of 6-12 inches. At upper elevations, variable and wind effected snow will be encountered.

 

Weather and Current Conditions

Weather Summary

A beautiful, sunny day should be expected for this fine Wednesday. Daytime highs are creeping upward through Thursday this week and winds are looking light and variable. Friday evening marks our next best chance at precipitation. Enjoy a couple nice days while we've got them.

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In Mt Shasta City at 0500, we have a current temperature of 23 F.

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

Old Ski Bowl - 7,600ft, the current temperture is 17 degrees F.  Temperatures have ranged from 8 F to 30 F.  Snow on the ground totals 187 inches with no new snow and 3 inches of settlement.

Gray Butte - 8,000 feet, the current temperature is 16 degrees F. Temperatures have ranged from 11 F to 32 F.  Winds have been predominantly NW averaging 15-20 mph with gusts to 30 until about 0700 yesterday when winds calmed considerably and have remained light and variable.

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

Castle Lake - 5,800 feet, the current temperature is 23 degrees F. Temperatures have ranged from 17 F to 34 F. Snow on the ground totals 109 with no new snow and 1 inch of settlement.

Mt Eddy - 6,500 feet, the current temperature is 20 degrees F. Temperatures have ranged from 14 F to 27 F. Snow on the ground measures 107 inches with no new snow and  1 inch of settlement. Winds have been calm, averaging 2 mph with gusts up to 12,  out of the southwest.

THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 43.31 inches of water, normal is 29.50 inches, putting us at 146% of normal.  For the month of February, we have received 11.05 inches of water, normal is 7.23, which is 152% of normal. And finally for the year of 2017, we received 22.15 inches of water, normal is 14.29 inches, putting us at 155% 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: 20
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: 10-15 mph, becoming 0-5 mph in afternoon mi/hr
Maximum wind gust in the last 24 hours: 30 mi/hr
New snowfall in the last 24 hours: 0 inches
Total snow depth: 119 inches

Two Day Mountain Weather Forecast

Produced in partnership with the Medford NWS

For 7000 ft to 9000 ft
  Wednesday
(4 a.m. to 10 p.m.)
Wednesday Night
(10 p.m. to 4 a.m.)
Thursday
(4 a.m. to 10 p.m.)
Weather Sunny Mostly clear Sunny
Temperature (°F) 42 24 43
Wind (mi/hr) Northeast 5-10 mph East/Southeast 5-7 mph South/Southeast 7-10 mph
Precipitation SWE / Snowfall (in) / 0 / 0 / 0
For 9000 ft to 11000 ft
  Wednesday Wednesday Night Thursday
Weather Sunny. Breezy. Wind chill values as low as zero. Mostly clear. Breezy. Sunny. Breezy.
Temperature (°F) 22 22 26
Wind (mi/hr) Northwest 15-20 mph West 0 West 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.