Avalanche Advisory: Tuesday - Apr 9, 2019

THIS AVALANCHE ADVISORY EXPIRED ON April 10, 2019 @ 6:59 am
Avalanche Advisory published on April 9, 2019 @ 6:59 am
Issued by Josh Feinberg - Eastern Sierra Avalanche Center

*This Avalanche Advisory is in effect for April 9th & 10th – Danger ratings will no longer be formally issued as they can change over multiple day periods*

Tuesday:  April showers bring May Flowers – A typical windy spring-time storm is upon us with 1-3” of snow last night, and up to 2” more possible by this afternoon at higher elevations and various forms of frozen pellets and rain at lower elevations.  Wet avalanches are a concern for lower elevations, and fresh wind slabs are a concern for mid to upper elevations.  Human triggered avalanches will be possible in specific areas.

Wednesday: Full sunshine, cooler temperatures, and a switch to strong north winds will make mid to upper elevation wind slabs a concern for all aspects, and small loose-wet avalanches a concern for E-S-W facing sunny aspects. Human triggered avalanches will be possible in specific areas.      

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Avalanche Problem 1: Wind Slab
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Tuesday:  Strong SW winds gusting into the 90s over ridge tops are accompanying new snowfall.  Fresh snow can be seen blowing over the ridge tops of the Sherwins at dawn this morning. Fresh sensitive wind slabs will likely be found at mid to upper elevations on the leeward side of ridges, sidewalls of gullies and around other features that promote drifting.  Watch for clues such as blowing snow and cornice formation to help determine where these new wind slabs may exist.  While likely to be relatively small, triggering a wind slab today could be bad news in consequential terrain where rocks, cliffs and trees are involved, or where a slope ends in a gully or depression.

Wednesday:  Strong winds switching out of the north Tuesday night thru Wednesday will lead to new fresh sensitive wind slabs developing at mid to upper elevations on more southerly aspects.  Lingering wind slabs that formed on Tuesday may still be sensitive in isolated areas.  Wind slabs on sunny aspects could become more sensitive thru the day as sunshine warms them.  Do your own localized assessments of denser wind deposited areas before entering committing terrain.  

Avalanche Problem 2: Loose Wet
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Tuesday: Rain fell last night and early this morning at lower elevations and up beyond 9,000’.  This combined with warm overnight temperatures and cloudy skies means that many lower elevation slopes will be wet, soggy and unstable this morning right off the bat on all aspects.  Avoid being on steep slopes that are not supportable, and realize that shallow wet surface sloughs could easily entrain enough snow to carry a person off their feet.  As temperatures and snowlines drop thru the day, this will become less of a concern.  

Wednesday:  Clearing skies and cold temperatures Tuesday night will mean a solid refreeze of most slopes.  Even with cool high temperatures on Wednesday, full sunshine will warm E to S to W facing slopes thru the day making areas with new snow deposits around rock bands susceptible to loose-wet point releases.  Be aware of what lies overhead!

advisory discussion

Unsettled spring time weather can mean rapidly changing conditions.  With new snow and wind, sensitive wind slabs can form and settle quickly.  Fluctuating temperatures, sunshine and clouds can make a totally stable slope concerning in a matter of hours, then can stabilize quickly again as it cools. Timing is everything, pay attention to the conditions surounding you.  Make a good plan, but be sure to stay flexible.    

Weather and CURRENT CONDITIONS
weather summary

Tuesday:  Mixed precipitation will continue thru most of the day in the form of snow, rain and various forms of frozen pellets depending on elevation.  High snow lines of over 9500’ will gradually fall this morning as a cold front pushes thru our area, with highs expected just below freezing around 10,000’.   Up to 2” of snow could fall during the day at higher elevations, mostly in the morning hours with scattered snow showers continuing in the afternoon. Strong SW winds gusting well into the 80s over ridge tops will decrease thru the day to more moderate levels before switching out of the north tonight and increasing once again.  Clouds should dissipate overnight, with lows expected in the upper teens near 10,000’.  

Wednesday:  A clear and sunny day is on tap for Wednesday, with well below average seasonal temperatures staying below freezing around 10,000’ and stout north winds. 

Unsettled weather returns for Thursday and Friday, with more chances of light precipitation.            

Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 8,000 ft. to 10,000 ft.
Tuesday Tuesday Night Wednesday
Weather: Mostly cloudy then becoming partly cloudy. Chance of snow in the morning, then scattered snow showers and slight chance of thunderstorms in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 55%. Mostly cloudy then becoming partly cloudy. Slight chance of thunderstorms and isolated snow showers in the evening. Snow levels below 7000 feet. Chance of precipitation is 20%. Sunny.
Temperatures: 30 to 40. deg. F. 15 to 21. deg. F. 30 to 40. deg. F.
Mid Slope Winds: West 15 to 30 mph with gusts to 50 mph. North 15 to 30 mph with gusts to 50 mph. North 15 to 30 mph with gusts to 50 mph.
Expected snowfall: 70% probability up to 2 inches. 30% probability no accumulation. | SWE = up to 0.15 inch. in. No accumulation. | SWE = less than 0.10 inch. in. 0 in.
Over 10,000 ft.
Tuesday Tuesday Night Wednesday
Weather: Mostly cloudy then becoming partly cloudy. Snow likely in the morning, then widespread snow showers and slight chance of thunderstorms in the afternoon. Snow levels below 7000 feet. Chance of precipitation is 70%. Mostly cloudy then becoming clear. Slight chance of thunderstorms and isolated snow showers in the evening. Snow levels below 7000 feet. Chance of precipitation is 20%. Sunny.
Temperatures: 24 to 32. deg. F. 10 to 15. deg. F. 23 to 31. deg. F.
Ridge Top Winds: Southwest 35 to 60 mph with gusts to 75 mph becoming west 20 to 30 mph with gusts to 45 mph in the afternoon. North 30 to 45 mph with gusts to 65 mph. North 30 to 45 mph decreasing to 25 to 35 mph in the afternoon. Gusts up to 60 mph.
Expected snowfall: up to 2 inches. | SWE = up to 0.20 inch. in. up to 1 inch. | SWE = less than 0.10 inch. 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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