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Avalanche Advisory for 2017-02-03 06:57:01

  • EXPIRED ON February 4, 2017 @ 6:57 am
    Published on February 3, 2017 @ 6:57 am
  • Issued by Nick Meyers - Shasta-Trinity National Forest

Strong winds with blizzard conditions are certain near and above treeline today. Wind slabs from yesterday will continue to grow in size and distribution as southwesterly flow and moderate to high intensity snowfall occurs over the forecast area. Expect increasing avalanche danger today and as one gains elevation... LOW danger below treeline, MODERATE near treeline and CONSIDERABLE above treeline. Short periods of HIGH danger are possible above treeline late this afternoon.

 

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.

Forecast Hotline: (530) 926-9613

Avalanche Problem 1: Wind Slab

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    Certain
    Very Likely
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  • Size ?
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Near and mostly above treeline, wind slabs will continue to build in size and distribution today. Southwesterly flow will primarily load NW-N-NE-E slopes, but slabs could occur on some W and SE aspects as well. Wind slabs could be 1-2 feet thick by the end of the day. Use clues such as blowing snow, new cornice formations, and newly formed wind pillows to identify and avoid slopes with likely wind slab development.

 

Forecast Discussion

Wind slabs will pose the greatest threat to backcountry riders and sliders today. Storm slabs are unlikely. Loose wet avalanches are possible from rain on new snow, but will probably not be large enough to pose a threat for folks. Lower elevation, steep slopes accompanied by a terrain trap would be the only place I could see a loose wet avalanche being a problem.

We have no end in sight for a period of mild winter weather for town and snow and wind in the mountains. Snow levels will take short forays up and down between 4 and 6,000 feet over the next several days. Several inches of water and continued high upper mountain wind is expected for the weekend. Roads access is still limited to McBride Springs along the Everitt Memorial Highway and the gate along the Castle Lake road. 

Riding snowmobiles up on Mt Shasta? It is your responsibility to know the boundaries. Get a map at Bunny Flat or stop by the Mt Shasta Ranger station. Thanks!

Recent Observations

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Snow levels this morning hover right around 6,000 to 6,500 feet with moderate south/southwest/southeast winds at low and mid elevations and high winds at upper elevations. Yesterday yielded a warm, rainy day. A tour up Grey Butte gave way to 2-5 inches of new snow with high moisture content below 7,800 feet. Precipitation below this elevation was in the form of wet snow and turning to rain at about 5,500 feet. At approximately 7,500 to 8,000 feet, our widespread and mostly supportable melt-freeze crust begins to fade. Some signs of wind loading was observed, but nothing significant in this area. Above treeline, it is likely different. 

 

Weather and Current Conditions

Weather Summary

The center of low pressure continues to sit off the coast of Oregon this morning and feed us warm, wet and windy weather. This low will spin off several disturbances today, sending them onshore in the form of rain, wind and high elevation snow. Tonight, expect the low pressure to begin to move east/northeast and be followed by gusty winds and yet another disturbance with the southwest flow aloft. Precipitation amounts will be greatest to the west and diminish to the east. Expect steady precipitation and very windy mountain conditions for today and the weekend. Rain and snow will taper off tonight, remain showery for the weekend and pick back up Sunday afternoon/evening. Snow levels are going to stay in the 5,000 to 6,000 foot range.

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In Mt Shasta City at 0500, we have a current temperature of 42 F.

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

Old Ski Bowl - 7,600ft. the current temperature is 29 degrees F. Temperatures have ranged from 23 F to 30 F. Snow on the ground measures 146 inches with 5 inches of new snow and little settlement.

Grey Butte - 8,000 feet, the current temperature is 29 degrees F. Temperatures have ranged from 22 F to 29 F.  Winds have averaged 10-20 mph with gusts to 42 mph, blowing out of the S/SW/SE.

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

Castle Lake - 5,600 feet, the current temperature is 33 degrees F. Temperatures have ranged from 27 F to 34 F. Snow on the ground totals 90 inches with perhaps a trace of new snow and then rain on snow after 1900 hrs.

Mt Eddy - 6,500 feet, the current temperature is 32 degrees F. Temperatures have ranged from 26 F to 32 F. Snow on the ground measures 77 inches with 4 inches of new snow and then 1 inch of settlement due to mixed rain and heavy snow after 1900 hrs.  Winds have averaged 2-3 mph with gusts to 14 mph, southwest in nature.

THIS SEASON PRECIPITATION for MT SHASTA CITY: Since October 1st (the wet season), we have received 32.93 inches of water, normal is 22.75 inches, putting us at 144% of normal.  For the month of February, we have received .67 inches of water, normal is .48, which is 139% of normal. And finally for the year of 2017, we received 11.77 inches of water, normal is 7.54 inches, putting us at 156% 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)
Weather Station Map
Weather Station Table
0600 temperature: 32
Max. temperature in the last 24 hours: 32
Average wind direction during the last 24 hours: S/SW/SE
Average wind speed during the last 24 hours: 10-15 mi/hr
Maximum wind gust in the last 24 hours: 20 mi/hr
New snowfall in the last 24 hours: 2-4 inches
Total snow depth: 90 inches

Two Day Mountain Weather Forecast

Produced in partnership with the Medford NWS

For 7000 ft to 9000 ft
  Friday
(4 a.m. to 10 p.m.) 		Friday Night
(10 p.m. to 4 a.m.) 		Saturday
(4 a.m. to 10 p.m.)
Weather Rain and snow, becoming all snow after 10am. The rain and snow could be heavy at times. Windy. Chance of precipitation is 100%. Snow. Breezy. Chance of precipitation is 100%. Snow. Breezy. Chance of precipitation is 100%.
Temperature (°F) 32 30 32
Wind (mi/hr) South 20-25 mph South 20-25 mph South 15-20 mph
Precipitation SWE / Snowfall (in) / 6-8 / 3-5 / 3-6
For 9000 ft to 11000 ft
  Friday Friday Night Saturday
Weather Snow. The snow could be heavy at times. Wind chill values as low as -7. Windy. Chance of precipitation is 100%. Snow. The snow could be heavy at times. Wind chill values as low as -9. Windy. Chance of precipitation is 100%. Snow. Wind chill values as low as -9. Windy. Chance of precipitation is 100%.
Temperature (°F) 19 17 17
Wind (mi/hr) Southwest 45-55 mph Southwest 9-11 Southwest 45-55 mph
Precipitation SWE / Snowfall (in) / 9-11 / 6-8 / 7-9

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.