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Avalanche Advisory for 2018-03-13 07:01

  • EXPIRED ON March 14, 2018 @ 7:01 am
    Published on March 13, 2018 @ 7:01 am
  • Issued by Andrew Kiefer - Mt Shasta Avalanche Center
  • March 13, 2018 @ 7:01 am

    Advisory Hotline: (530) 926-9613

  • Dangerous avalanche conditions exist in the backcountry. Wind slab, storm slab and wet loose avalanche problems are all significant concerns. Gale force winds, rain and heavy snowfall will create challenging conditions and poor visibility. Expect heightened avalanche danger as snowfall continues through the end of the week.

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

Avalanche Problem 1: Wind Slab

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Heavy snow and very strong southerly winds have created fresh wind slabs in leeward terrain near and above treeline. Wind slabs will continue to grow in size and distribution today. Human triggered wind slab avalanches are likely. Stick to protected or wind scoured areas to avoid the wind slab problem and steer clear of wind loaded slopes 35 degrees and steeper.

Avalanche Problem 2: Storm Slab

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Watch for storm slabs to develop this afternoon as snow levels lower and several inches of new snow accumulate. Storm slabs form in sheltered areas where new snow falls with light winds. They can occur on any steep open slope, and are often found on several aspects at the same time. They are easiest to trigger during periods of heavy snow and typically stabilize after the storm cycle has ended. Reduce your risk from storm slabs by waiting a day or two after a storm before venturing into steep avalanche terrain.

Avalanche Problem 3: Loose Wet

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Wet loose avalanches will be possible on steep slopes near and below treeline. Watch for roller balls and pinwheels as evidence of weakening snow surfaces. Avoid slopes where these signs are present. Wet loose avalanches can entrain a surprising amount of snow as they gain momentum and move down slope.

Advisory Discussion

We are in the midst of a potent storm that will bring rapid snow accumulation and very high winds over the next 24 hours. Limited visibility and several avalanche problems will make backcountry travel challenging. Careful snowpack evaluation, cautious route finding and conservative decision-making are essential today.

Recent Observations

Precipitation began at 10 pm last night. As of 6 am this morning, the Old Ski Bowl has received .55 inches of water translating to 1 inch of new snow. Grey Butte has recorded strong S/SE winds with gusts over 40 mph. Temperatures at 8,000 ft remained above freezing overnight, but are cooling already this morning. Overnight, Mount Shasta City received .27 inches of rain. 

The riding conditions on the Tri-Forest Snowmobile Trails were good yesterday. Most trails have been recently groomed, and ungroomed trails were smooth and easy to ride. CLICK HERE to read the full observation.

Weather and Current Conditions

Weather Summary

A strong frontal system will move through the area today bringing gale force winds and heavy snow to the upper mountain. The storm has been warm and wet so far, but will cool off this afternoon. Snow levels will be near 7,000 ft, lowering to 4,500 ft tonight. Another 1.5 inches of water is expected over the next 24 hours. Snow totals will vary dramatically with elevation today: rain below 4,500 ft, 5-9 inches up to 8,500 ft, and 1-2 ft above 8,500 ft. South winds will gust well over 60 mph near and above treeline and visibility will be very limited. Temperatures will remain cold through the rest of the week and snow showers will continue.  

24 Hour Weather Station Data @ 6:00 AM

Weather Station Temp (°F) Wind (mi/hr) Snow (in) Comments
Cur Min Max Avg Avg Max Gust Dir Depth New Water Equivalent Settlement
Mt. Shasta City (3540 ft) 48 34 55 43 4 SE
Sand Flat (6750 ft) station down
Ski Bowl (7600 ft) 32 28.5 38.5 34 59.5 1 0.55 2
Gray Butte (8000 ft) 33 27.5 35.5 32.5 15 42 SSE
Castle Lake (5870 ft) 40.5 33 44.5 38.5 24 0 1.5
Mount Eddy (6509 ft) 35 31 38.5 36 3 23 WSW 40.5 1 1
Ash Creek Bowl (7250 ft) station down
Ash Creek Ridge (7895 ft) station down

Two Day Mountain Weather Forecast

Produced in partnership with the Medford NWS

For 7000 ft to 9000 ft
  Tuesday Tuesday Night Wednesday
Weather Rain and snow becoming all snow after 2pm. Windy. Snow showers. Chance of precipitation 100%. Snow showers. Chance of precipitation 90%.
Temperature (°F) 37 23 27
Wind Direction S S W
Wind Speed (mi/hr) 15-20 mi/hr 10-15 mi/hr 5-10 mi/hr
Expected Snowfall (in) 5-9 4-8 3-6
For 9000 ft to 11000 ft
  Tuesday Tuesday Night Wednesday
Weather Heavy snow and windy Heavy snow and windy Snow showers and breezy. Chance of precipitation 80%
Temperature (°F) 22 7 8
Wind Direction S S/SW W
Wind Speed (mi/hr) 60-70 mi/hr 40-50 mi/hr 15-25 mi/hr
Expected Snowfall (in) 18-24 4-8 3-6

Season Precipitation for Mount Shasta City

Period Measured (in) Normal (in) Percent of Normal (%)
From Oct 1, 2017 (the wet season) 12.75 32.37 39
Month to Date (since Jun 1, 2018) 1.86 2.87 65
Year to Date (since Jan 1, 2018) 6.92 17.16 40

Disclaimer

This advisory does not apply to Ski Areas or Highways and is for the Mount Shasta, Castle Lake and Mount 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.