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Avalanche Advisory for 2018-04-10 06:33
- EXPIRED ON April 11, 2018 @ 6:33 amPublished on April 10, 2018 @ 6:33 am
- Issued by Aaron Beverly - Mount Shasta Avalanche Center
Avalanche Problem 1: Wind Slab
Likelihood ?CertainVery LikelyLikelyPossible
Size ?HistoricVery LargeLarge
Small wind slabs may begin to form above treeline this afternoon on west, north, and east aspects. Smooth firm snow surfaces exist that will provide ideal bed surfaces for avalanches. These will unlikely be large enough to bury a person, but could be touchy to trigger and may cause a slide for life situation down steep icy slopes.
Avoid wind slabs by traveling in windward areas where snow surfaces have been eroded. Avoid slopes greater than 35 degrees where wind loading has occurred. Evaluate conditions as you travel in safe terrain by looking for signs of the wind slab problem:
- Smooth rounded wind pillows
- Hollow sounding snow
- Harder snow atop softer snow
- Shooting cracks
Smooth snow surfaces exist on all aspects. A cooling weather pattern means these surfaces will stay icy during the day. An ice axe and crampons are mandatory for climbing up steep terrain. Self-arrest will be difficult in these conditions.
Active icefall was observed yesterday and many grapefruit sized ice balls were seen in gullies below Helen Lake. Colder weather will keep this at bay, but be prepared for it nonetheless. Wear a helmet!
Winds could reach gale force velocities. Be ready to receive a pummeling if venturing above treeline today.
No new snow was received last night. The temperature reached a high of 53 °F at the Old Ski Bowl weather station.
Yesterday, Avalanche Gulch hosted near perfect corn skiing conditions on all aspects by 2:30 p.m. Snow surfaces were smooth. Thin layers of soft corn snow sat atop firm consolidated snow. Small roller balls could be ski-triggered on aspects exposed to direct sun, but there were no natural signs of wet loose activity. Westerly aspects were extremely icy in the morning. A hiker/climber was observed taking a hair-raising slide off of Green Butte Ridge. Person was uninjured. Grapefruit sized balls of ice were seen in gullies below Helen Lake and ice fall was active out of Red Banks and the Trinity Chutes.
Weather and Current Conditions
A weak warm front moves in from the coast today. Precipitation at near and below treeline elevations will see this in the form of rain and wet snow. Snow levels look to be 8000-9000 ft. Above treeline, 2-3 inches of snow is possible. South winds could reach speeds above 50 mi/hr.
A stronger front moves in tomorrow bringing colder temperatures and the possibility of several inches of snow above 5000 ft.
24 Hour Weather Station Data @ 4:00 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)||52||31||73||57.5||2||N|
|Sand Flat (6750 ft)||station down|
|Ski Bowl (7600 ft)||37.5||37.5||52.5||44.5||73.5||0||0||1.5|
|Gray Butte (8000 ft)||36.5||36.5||52||44.5||8||31||ESE|
|Castle Lake (5870 ft)||station down|
|Mount Eddy (6509 ft)||41||34.5||57||47||2||11||SSW||37.5||0||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|
|Weather||Rain. Windy. Chance of precipitation is 80%.||A chance of rain and snow showers before 11 p.m., then a slight chance of snow showers. Mostly cloudy. Chance of precipitation is 30%.||Snow. Breezy. Chance of precipitation is 100%.|
|Wind Speed (mi/hr)||15-20||10-15||15-20|
|Expected Snowfall (in)||0||<0.5||2-4|
|For 9000 ft to 11000 ft|
|Weather||Snow. Windy. Chance of precipitation is 80%.||A 30 percent chance of snow showers, mainly before 11 p.m. Mostly cloudy. Wind chill values as low as -7. Windy.||Snow. Wind chill values as low as -11. Windy. Chance of precipitation is 90%.|
|Wind Speed (mi/hr)||50-60||30-35||40-45|
|Expected Snowfall (in)||2-3||<0.5||2-4|
Season Precipitation for Mount Shasta City
|Period||Measured (in)||Normal (in)||Percent of Normal (%)|
|From Oct 1, 2017 (the wet season)||17.17||36.47||47|
|Month to Date (since Apr 1, 2018)||1.22||1.01||121|
|Year to Date (since Jan 1, 2018)||11.34||21.26||53|