Avalanche Advisory: Monday - Dec 9, 2019

THIS AVALANCHE ADVISORY EXPIRED ON December 10, 2019 @ 6:33 am
Avalanche Advisory published on December 9, 2019 @ 6:33 am
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

Wind slabs at mid to upper elevations on all aspects will be the primary concern for the beginning of this week. Recent snowfall combined with extreme WSW winds and more recent (Sunday afternoon/night into Monday morning) backing Easterly & Northerly winds will transport and load snow to a multitude of aspects and terrain features.

 

Danger Ratings cannot be assigned accurately for multi-day advisories as conditions can change drastically from one day to the next. Daily Advisories with danger ratings will begin on December 20th.*

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Above Treeline

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Near Treeline

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Below Treeline
advisory discussion

Expect fresh wind slabs primarily on northerly and easterly aspects, but be aware that wind direction changed Sunday night into Monday blowing from the East and North which will redistribute snow to the sunny aspects of South and West. Upper elevations above tree line are of highest potential hazard, with recent extreme storm winds (W-SW) and snow totals reaching over a foot on Saturday/Sunday. There were some observations of skier triggered winds slabs 6-8” in depth Saturday during the storm in the Mammoth and the Virginia Lakes area. On Sunday, natural slab avalanches, some reaching the D2 category were  observed  in the McGee Creek/Nevahbe ridge area near Crowley. Local reports in the Mammoth area also described loose-snow sloughing in extreme and confined terrain, including some which would be enough to drag or injure a rider.

Approach the high country with care and focused attention on wise terrain choice both up and down this week.  With Monday’s forecasted sunny skies and access opening up, conditions will be enticing to explore higher elevations of the zone. Keep in mind that you’re more than likely the first person up there this winter season and at this point, there is scant information recorded in the alpine zone.  Be on the lookout for recent avalanches, blowing snow, recent cornice growth, and fat, pillowed snow surfaces. All these clues can help you identify and steer clear of recent fresh wind deposits and potential wind slab or new snow avalanche conditions.

Perform your own local assessments and be wary of terrain features that are conducive to capturing drifting snow such as the leeward sides of ridgelines, gully features, and cross-loaded depressions.  More extreme terrain features such as steep, walled in couloirs and convexities will present some of the greatest areas of hazard or potential wind slab instabilities or loose snow sloughing.

Snow coverage across the zone is highly variable with the bull’s-eye for the deepest base being in the Mammoth area right now.  Don’t lose sight that it’s still early and there are a lot of submerged obstacles and hazards everywhere. Keep It Real with terrain choice and focus on a season long program of fun to come.

Weather and CURRENT CONDITIONS
weather summary

Sunny skies and warmer temps (above freezing) for Monday and the majority of Tuesday. Monday night should be cold and clear with temps in the teens and the return of light SW winds.  Cloudy and overcast conditions come back in Tuesday evening/night and Wednesday morning.  Clouds associated with a low pressure system will roll into the area providing light snow showers (dusting up to 1”) in the mountains Tuesday night. An active pattern is forecasted as another system with a modest moisture tap is slated for the end of the week into the weekend. Additional potential storms are modeled for the middle of December as well!

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Monday Monday Night Tuesday
Weather: Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%. Clear. Snow levels below 7000 feet. Chance of precipitation is 0%. Partly cloudy then becoming mostly cloudy. Snow levels below 7000 feet. Chance of precipitation is 0%.
Temperatures: 33 to 38. deg. F. 14 to 19. deg. F. 36 to 41. deg. F.
Mid Slope Winds: Light winds. Light winds. Light winds. Gusts up to 25 mph in the afternoon.
Expected snowfall: 0 in. 0 in. 0 in.
Over 10,000 ft.
Monday Monday Night Tuesday
Weather: Sunny. Snow levels below 7000 feet. Chance of precipitation is 0%. Clear. Snow levels below 7000 feet. Chance of precipitation is 0%. Partly cloudy then becoming mostly cloudy. Snow levels below 7000 feet increasing to 7000 feet in the afternoon. Chance of precipitation is 0%.
Temperatures: 29 to 35. deg. F. 11 to 16. deg. F. 31 to 36. deg. F.
Ridge Top Winds: Northwest around 15 mph. Light winds becoming southwest around 15 mph with gusts to 25 mph after midnight. Light winds becoming southwest around 15 mph with gusts to 25 mph in the afternoon.
Expected snowfall: 0 in. 0 in. 0 in.
Disclaimer
This Avalanche Advisory is designed to generally describe avalanche conditions where local variations always occur. This product only applies to backcountry areas located outside established ski area boundaries. The information in this Avalanche Advisory is provided by the Eastern Sierra Avalanche Center, who is solely responsible for its content.

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