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Avalanche Advisory for 2017-02-28 06:45:00

  • EXPIRED ON March 1, 2017 @ 6:45 am
    Published on February 28, 2017 @ 6:45 am
  • Issued by Aaron Beverly - Mount Shasta Avalanche Center

This morning the avalanche danger is CONSIDERABLE near and above treeline due to wind slab formation on leeward aspects.  Pay attention to where wind loading has occurred and is still occurring.  When in doubt, stay on slopes less than 30 degrees. Loose sloughs and storm slabs are less likely to be a problem, but stay aware of their potential. Avalanche danger below treeline is MODERATE on steep terrain exposed to the effects of the wind.

 

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

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.

Avalanche Problem 1: Wind Slab

  • Character ?
  • Aspect/Elevation ?
  • Likelihood ?
    Certain
    Very Likely
    Likely
    Possible
    Unlikely
  • Size ?
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    Very Large
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Moderate to strong NW winds continued to transport light surface snow over the last 24 hours creating new hard wind slabs at least 6 inches thick both below, near and above treeline. Predominant loading has been observed on east and southeast facing slopes and winds today will continue to load these aspects above treeline. Mountain winds are variable, and loading has likely occured on other aspects, so pay attention whenever entering steep terrain.

Forecast Discussion

Although the primary concern today are wind slabs, keep an eye out for storm slabs in sheltered areas below treeline. A couple of shallow storm slabs were observed on Sunday afternoon. Snow has settled quickly and in isolated areas this may have created a consolidated layer atop a weaker layer within the newest storm snow.

Temperatures have stayed cold and there is plenty the surface snow that remains light and unconsolidated particularly on northerly aspects. This could lead to sloughs in steep terrain. These are typically not dangerous, but could sweep a skier off his or her feet.

Remember to excerise caution and when in doubt, stick to slopes under 30 degrees.

Recent Observations

Moderate to strong SW to NW winds were observed yesterday above and below treeline which was transporting plenty of snow to leeward slopes. Backcountry travelers noted new wind slabs forming up to 6-8 inches thick on south and southeastern aspects both above and below treeline. Some slabs were 2 - 3 feet thick, though it is unclear if these were new or old slabs. On the east side of Coyote Butte (Mt Shasta Ski Park), new wind slabs were well bonded with the old snow and could not be triggered to slide. Above treeline skiers observed hollow feeling snow in wind effected areas. No natural or human-triggered avalanches were observed.

Weather and Current Conditions

Weather Summary

The effects of the low pressure system off the coast of Washington will continue to bring in cold air from the Gulf of Alaska today keeping snow levels below 2000'. Tomorrow a high will begin pushing in warmer air from the west. Snow levels will rise to above 5000' and we'll have a few days of clear weather. Get out and enjoy the last of that Utah-style powder. It'll be gone soon. Expect the return of wet warm storms on Friday. 

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

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

Old Ski Bowl - 7,600ft, the current temperture is 15 degrees F.  Temperatures have ranged from 2 F to 15 F.  Snow on the ground totals 190 inches with about an 1 inch of new snow 1 inch of settlement

Gray Butte - 8,000 feet, the current temperature is 13 degrees F. Temperatures have ranged from 9 F to 21 F.  Winds have been predominantly NW averaging 14 mph with gusts to 35 mph.

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

Castle Lake - 5,800 feet, the current temperature is 17 degrees F. Temperatures have ranged from 14 F to 33 F. Snow on the ground totals 110 with a trace of new snow and 1.5 inches of settlement.

Mt Eddy - 6,500 feet, the current temperature is 15 degrees F. Temperatures have ranged from 10 F to 25 F. Snow on the ground measures 108 inches with no new snow and  4 inches of settlement. Winds have been calm, averaging 2 mph with gusts up to 10,  and variable.

THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 43.31 inches of water, normal is 29.23 inches, putting us at 148% of normal.  For the month of February, we have received 11.05 inches of water, normal is 6.96, which is 159% of normal. And finally for the year of 2017, we received 22.15 inches of water, normal is 14.02 inches, putting us at 158% 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: 15
Max. temperature in the last 24 hours: 23
Average wind direction during the last 24 hours: NW
Average wind speed during the last 24 hours: 14 mi/hr
Maximum wind gust in the last 24 hours: 35 mi/hr
New snowfall in the last 24 hours: 1 inches
Total snow depth: 120 inches

Two Day Mountain Weather Forecast

Produced in partnership with the Medford NWS

For 7000 ft to 9000 ft
  Tuesday
(4 a.m. to 10 p.m.)
Tuesday Night
(10 p.m. to 4 a.m.)
Wednesday
(4 a.m. to 10 p.m.)
Weather Scattered snow showers before 10 am. Partly sunny. 30% chance of precipitation. Mostly clear. Clear and sunny
Temperature (°F) 33 21 44
Wind (mi/hr) West Northwest 6-8 mph North Northeast 2-5 mph East Northeast 2-5 mph
Precipitation SWE / Snowfall (in) / Trace / 0 / 0
For 9000 ft to 11000 ft
  Tuesday Tuesday Night Wednesday
Weather Scattered snow showers before 10 am. Partly sunny. Chance of precipitation 30%. Mostly clear and windy. Clear, sunny and windy.
Temperature (°F) 15 15 25
Wind (mi/hr) Northwest 21-27 mph North Northwest Trace Northwest - West Northwest 13-17 mph
Precipitation SWE / Snowfall (in) / Trace / 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.