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Winter Storm Warning

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avatar Winter Storm Warning
January 28, 2021 08:18AM
URGENT - WINTER WEATHER MESSAGE
National Weather Service Hanford CA
759 AM PST Thu Jan 28 2021

CAZ190>194-290100-
/O.CON.KHNX.WS.W.0002.000000T0000Z-210129T1200Z/
Central Sierra Foothills-Southern Sierra Foothills-Central Sierra-
North Kings River-Sequoia Kings-
Including the cities of Coarsegold, Oakhurst, Squaw Valley,
Auberry, North Fork, Mariposa, Springville, Three Rivers,
Devils Postpile, Florence Lake, Lake Thomas Edison,
Tuolumne Meadows, Bass Lake, Fish Camp, Wawona, Shaver Lake,
Camp Nelson, Giant Forest, Lodgepole, Grant Grove,
and Johnsondale
759 AM PST Thu Jan 28 2021

...WINTER STORM WARNING REMAINS IN EFFECT UNTIL 4 AM PST FRIDAY...

* WHAT...Total new snow accumulation of 2 to 5 feet expected above
7,000 feet, with as much as 4 to 12 inches possible down to
4,500 feet. Winds gusting around 55 mph.

* WHERE...Central Sierra, North Kings River, Central Sierra
Foothills, Southern Sierra Foothills and Sequoia Kings
Counties.

* WHEN...Until 4 AM PST Friday.

* IMPACTS...The hazardous conditions will impact travel across
mountainous areas. Strong winds may cause power poles, trees,
and limbs to blow down. Visibilities may be reduced in heavy
snowfall and blowing snow. Whiteout conditions are possible at
times.

* ADDITIONAL DETAILS...If you must travel, keep an extra
flashlight, food, and water in your vehicle in case of an
emergency. Prepare for possible power outages.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

If you must travel, keep an extra flashlight, food, and water in
your vehicle in case of an emergency. Prepare for possible power
outages.

The latest road conditions for the state you are calling from can
be obtained by calling 5 1 1.

&&

$$
Re: Winter Storm Warning
January 28, 2021 05:22PM
And this note about avalanches:

AVALANCHE ADVISORY PUBLISHED ON JANUARY 28, 2021 @ 6:48THIS ADVISORY IS VALID FOR 24 HOURS
Issued by Chris Engelhardt - Eastern Sierra Avalanche Center

EXTREME AVALANCHE DANGER exists today as a powerful winter storm impacts the Eastern Sierra. Heavy accumulations of new snow and loading southerly winds will build Slabs on All Aspects. Avoid all Avalanche terrain as natural and human triggered avalanches are certain.

6. Extreme [danger]
Above Treeline

6. Extreme
Near Treeline

6. Extreme
Below Treeline


AVALANCHE PROBLEM #1: WIND SLAB


ASPECT/ELEVATION [The Center provides an image of all aspects and elevations, and the risk was high on pretty much all aspects except South-South-west]


LIKELIHOOD-- Certain


SIZE-- Historic, Large
Strong to moderate southerly winds optimal for loading combined with massive amounts of new snowfall (4-6ft+) will be building reactive and deep wind slabs on virtually all aspects and elevations. W-N-E-SE will be aspects of primary concern with guaranteed wind slab development adjacent to ridgeline and terrain features conducive to capturing wind transported snow such as cliff bands, convex rollovers and gullies. Avalanches of all sizes and scope are nearly certain today. Large to very large avalanches have the potential to run into lower terrain where you may normally think you are safe. Avoid all avalanche terrain!
AVALANCHE PROBLEM #2: STORM SLAB


ASPECT/ELEVATION -- [All aspects]


LIKELIHOOD-- Certain


SIZE-- Historic, Large
Incredible amounts of new snow (4-6ft and likely more in some areas) fell Wednesday; snowfall was unrelenting through last night and will continue today. Fresh, sensitive, and unstable storm slabs on All Aspects at All Elevations are guaranteed to be present. In the midst of a storm of this magnitude avalanche conditions will be extremely dangerous as new snow will be looking to adjust its balance in relation to gravity and slope. This means avalanches in all forms, from soft sensitive slabs on virtually any slope with a bit of steepness, to loose dry point releases in very steep terrain.
AVALANCHE PROBLEM #3: PERSISTENT SLAB


ASPECT/ELEVATION -- [Northwest to Southeast]


LIKELIHOOD-- Certain (Now downgraded to "Very Likely."winking smiley


SIZE-- Historic , Large
This hefty storm is rapidly loading the shallow and loose-grained snowpack from November and December with a significant amount of weight. W-SE aspects all harbor weak structure from our prolonged drought through the first half of the winter. The rapid loading and large amount of weight in the new snow will likely cause collapse and failure in these old weaker layers. Avalanches originating from fresh unstable wind/storm slab and loose dry will add to the pressure on these weak persistent layers and could cause avalanches to “step down” into the older snowpack causing much bigger and destructive avalanches.:



Balzaccom

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