Winter through Spring Thaw, 2011-2012

Alex Wierbinski's picture

By Alex Wierbinski - Posted on 19 February 2012

Welcome to the Fall High Sierra Reports and Analysis

Below you will find my analysis of the progress of the weather into the ultra-dry Winter of 2011-2012. This bone-dry Winter followed the Winter of 2010-2011, which was one of the wettest and snowiest for decades. The snowpack never totally cleared from the Sierra Crest during the Summer of 2011... and now there is no Winter of 2012 snowpack.

Recent News Bits

California, Feds Ratcheting Back on Farm Water, KQED, Feb 22, 2012

Climate change, increasing temperatures alter bird migration patterns, University of North Carolina at Chapel Hill, Feb 23, 2012.

'Storm of the century' may become 'storm of the decade,' Princeton, Feb 23, 2012.

Classic Maya civilization collapse related to modest rainfall reductions, University of Southampton, Feb 23, 2012

Earliest horses show past global warming affected body size of mammals, University of Florida, Feb 23, 2012.

Yosemite's alpine chipmunks take genetic hit from climate change, UC Berk, Feb 20, 2012.

Ouick Notes on the Winter of 2011-2012

Mid February: A weak series of storm pulses out of the West-Northwest delivered almost no rain to the lowlands and little snow to the Sierra. There is little snow on the Sierra, and California has received around 30% of normal Winter precipitation. Skies are now sunny and clear. The Spring bloom has begun in mid Feb.

My experiences here indicate that 1 in 3 dry winters are "bailed out" by fierce Spring tropical storm activity out of the Southwest. For some reason I don't feel that we are going to get "bailed-out" by Spring storms out of the South this year.


Jan 19: Weak but wet storms blowing directly out of the West, straight across the Pacific Ocean from China. These weak rainstorms have finally broken a month of dry weather through the heart of Wintertime.


January 6, 2012: The Sierra remains bereft of snow, for the most part, while California "enjoys" historically unprecendeted clear skies and high temps. More on this below.

December 18, 2011. I'm looking forward to hearing about the Late Fall Conditions you encounter during your High Sierra backpacking trips. I'm still recovering from injury incurred last Winter. I need your reports to get my hiking fix.

(Much more below)


Mid-February 2012

Temps and conditions at this point in time indicate to me that full Winter Gear can be lightened to your Spring/Fall gear kit. Though it's still early in the year, Spring conditions are establishing themselves.

Gear selection must be dependent on solid temp information. Monitor the reporting stations near your route to determine the actual temps, carefully scan the forecasts, weather maps, predictions, and satellite information for indications of changing conditions.

Always pack gear for the worse possible conditions while hoping for the best. Despite the warm weather and because of the clear conditions nightime temps can still plunge to well below freezing. Though the skies say "June," it is still February, and conditions can still change rapidly.

January 6, 2012

At this point in Winter it is quite clear that Winter weight gear must replace your Fall gear kit. Don't let the clear skies and lack of snow fool you. It's getting Wintertime cold in the Sierra, and clear skies make for very cold nights. Winter temps have descended on the Sierra, even if Winter snows have not.

But here I'm concerned with providing you with the best information about Sierra weather and trail conditions possible. So you can anticipate the rapid changes in "trail" conditions that are now possible. My approach is to match my layering with the range of temps and conditions I anticipate. Check out the Gear page on the Trail guide and the Winter Gear Selection videos on YouTube.

The temps, weather, and snow condition reports you post to supplement the resources above are GOLD. There's no experience like real experience.

Rapidly Changing Conditions?

Mid-February 2012

Fine conditions can draw backpackers to the mountains like moths to the flame. Don't get burned. Though temps are rising, the threat of dangerous storms still looms, and must be considered before undertaking any Winter Travel into the Sierra.

One big plume of super-heated moisture from East of Hawaii, or from South of Baja that swings North across the Sierra can deposit THREE FEET of snow in one evening.

January 5, 2012

Winter conditions are deepening, bringing cooler temps but not yet even a threat of significant snow to the Sierra Nevada as of January 5, 2012. To me this means that conditions in the Sierra can and will change rapidly.

Just wait until the South Pacific throws a mass of super-heated tropical mositure at the Sierra. Three feet of snow can fall in one night.

You will need to anticipate the possibility of snow obscuring the trail and terrain along with deep cold conditions requiring thicker gear. You must be prepared and geared for the physical difficulities of unexpected snow travel.

Seriously, these conditions "on the ground" could change in a heartbeat due to the low temps in the Sierra. Any moisture that blows up there will come down as snow. Local storms and flurries that are not connected to any major storm fronts are regular events. Though "local" weather is generally limited in power, these mini-storms can cover the terain with a light coat of snow and ice.

Right now (January 5, 2012 ) up to a foot snow of old snow is sitting on the Sierra Crest, and most Summer Backpackers have stashed their gear for the season.

Other backpackers are pulling out their Winter Gear, but there is not enough snow in the Sierra to support snow-shoe or ski travel.

Good information is one of your most important assets . If you are well informed you will be well prepped for the potential of extreme conditions by being properly informed of the possible range of  conditions you can encounter. Expect the best, pack for the worse.

Knowing what weather possibilities are coming "over the horizon" before you begin a backpacking trip allows you to observe developing conditions with the knowledge of what the evolving conditions mean in terms of the possibilities you observed before departing.

The most important information you will need revolves around getting the best information about the deepening cold, impending threats of weather and storms, and road conditions. Check the weather and ground reporting stations listed above for real-time information up and down the Sierra crest, in the Sierra foothils, and on the High Sierra Roads.

Observations and Notes on the progress of the Season

Mid-February 2012

Though the last series of very weak storms came out of the Northwest, these storms did not pass across the Bearing Straights before heading South. These storms crossed the North Pacific well South of Alaska.

The winds are again coming out of  the Northwest, but not on a Winter pattern. These North winds are eminating from the great high pressure zone that has sat in the Southern Gulf of Alaska for most of this Winter. This high has again strongly reestablished itself.

I contend that the source of this high is the Hadley Cell that dumps its load in the Southern Gulf of Alaska. This particular Hadley Cell did not retreat during the Winter, and it is now producing Wind patterns more typical during Summer than Winter.

January 5. 2012

The prevailing winds continue to blow out of the West and Southwest, continuing the deepening long-term trend of non-traditional vectors for the prevailing Winter winds. The traditional direction of Winter winds coming out the the Northwest has been gradually replaced by Winter winds coming out of the West and Southwest.

 It also appears that the heat of Summer has not retreated South with the Sun. This is indicated by the West and Southwestern character of the prevailing winds, the huge persistant high sitting off of the Northwest Coast of the US, and the complete failure of any storm activity out of the Aleutians. 

It also appears that the spinning mass of frigid air circiling the Arctic is considerably warmer than historical norms.

The Arctic has lost its power as the generator of Winter weather patterns for the Western United States.

Mid December:

Cold temps have fallen on the Sierra, but very little snow. Strange weather patterns over the whole Northern Pacific are once again in action, with a big hot high pressure zone deflecting the normal flow of storms that comes down from Alaska far to the North of the Sierra.

This indicates to me that not only have the Hadley Cells not retreated significantly this Winter, they seem to be pumping significant Equatorial heat into the Northwest Pacific. The weather impacting the Western shore of the continential US is coming out of the Central Pacific.

A Hadley Cell is a large mass of superheated tropical air that travels North at high altitude from the Equator, arcing down to affect climate at high North latitudes. The Hadley Cell that affects the weather of the Western United States, and the Sierra Nevada Mountains, lands in the far South of the Gulf of Alaska. I had to learn the term "Hadley Cell" when I noticed the heat of Summer was not retreating as far South during Winter time. Twenty years ago.

Late November 2011:

As of late November a series of weak storms has put a dusting of snow up on the Sierra that's up to a foot thick in protected Eastern Sierra locations, such as Leavit Lake. Weather patterns are still being dominated by Western and Southwestern winds.

As of Oct 15 freakish high humidity, moist air, and heat from far South of Hawaii is crossing the Pacific Coast and Sierra Crest. Freakish weather dominated by air masses from the West and Southwest rather than the normal storm track out of the Northwest.  

As of Oct 5 the Sierra just experienced it's first dusting of snow. Everyone freaks out... Let's get some solid information from "on the spot" about snowfall, precipitation, and temps.


2011-2012 Weather Trends

Mid-February 2012

Spring conditions are strongly establishing themselves in California. The hope for storms out of the NW to break this Winter's drought are less than foolish. Not going to happen. The Stormgate is Closed.

The current trend is for mild weather as far as the eye can see.

The Southern Heat that is rearranging Sierra Winters is the only hope for bringing  enough precipitation to the Sierra for Nature, let alone man.

If we are lucky tropical storms will blow out of the SW to lay some late-season snow on the Sierra. Unless atmospheric conditions radically change, I can't see the North bringing  any significant additional precip this Winter & Spring.

All of our hopes for late-season rain are focused to our South, on the tropics, and I see the chances of that happening declining every day.

I now see the prospects of late season storms from the South declining to a 1 in 4 chance of significant precip bailing us out from the tropics.

January 6, 2012:

I consider December 21 the "middle" of the Winter, not the beginning. I guess it's just a matter of semantics. However you call it, now that the Sun is rising, we can say that the "storm gate" at the Bearing Straight & Aleutians did not open as the Sun was dropping during the approach of Winter.

The chances of storms coming out of the Northwest really declines after December 21.   There is still a chance of storms out of the Northwest blowing in, but it declines every day. The major hope for snow now relies on tropical moisture blowing out of the Equatorial and Tropical Pacific. This is not highly unlikely. I put the chances of big, wet, hot storms coming out of the Southwest during late Winter and early Spring at 1 in 3.

Traditionally, the Fall and Winter weather that deposits a deep snowy mantle on the Sierra comes out of the Northwest, composed of the moisture sucked up the the Arctic along the East Coast of Asia.

This Asian moisture is spun along the cold edge of the spinning mass of super-cold Arctic air across the Bearing Straight and over the Aleutians, and is cast down along the Western Coast of the US, bringing powerful North Pacific storms down as far South as San Diego. Those days appear to be over, at least as the baseline for Western US weather. Only "freak" years now manifest the old "normal" weather pattern. The traditional weather pattern over the North Pacific has been broken.

The increased strength and higher Winter position of our Hadley Cell seems to be making the traditional weather mechinism described above impossible. This new behavior of our Hadley Cell appears to have established itself strongly, and appears to have been strengthing during the 20 years I have observed the development of this new weather pattern.

Add the higher temps of the Arctic to the extra reach of tropical heat eminating North from the Tropics with the new character of our Hadley Cell, and you have a whole new weather system creating weather for the West Coast of the North American Continent from Alaska to San Diego. And the Sierra Nevada Mountains...

December 18:

The trend of winds blowing out of the West and Southwest could change in a heartbeat due to the low temps in the Sierra. pas continued.  The "stormgate" through the Bearing straight that feeds "normal" winter weather patterns in the Western US has still not opened, and does not look like it will. See the second paragraph below.

November 25:

The trend of the winds blowing from the West and Southwest has continued. The "stormgate" through the Bearing straight that feeds "normal" winter weather patterns in the Western US has not opened.

I say that the storm gate is damaged, if not broken. Arctic temp changes appear to have altered the mechanism itself by changing the interaction between the Western Pacific air flows that used to turn East across the Bearing Straight and be "charged up" by the spinning mass of frigid arctic air and cast down across the Western US. 

This mechanism has been trying to dominate our weather this season, but it contains insufficient energy to continue to dominate weather patterns in the Western US, and therefore the Sierra Nevada Mountains.

This does not necessairly mean less snow in the Sierra. This moist tropical air from the West and South can bring tremendous snowfalls when it's moist tropical air is forced over the cold crest of the Sierra Nevada Mountains.

Oct 5:

Do these first light storms of October represent the early end of this already radically shortened 2011 Summer Backpacking Season?

We saw Winter conditions persisting into Spring this year and Spring conditions pushed deep into the Summer. The Spring Thaw of 2011 page recorded the slow thaw of 2011.

Have these conditions made the Summer of 2011 one of the shortest backpacking seasons in recent memory? Maybe...


Predictions Impossible

Mid-February 2012

Right now we are looking at what could be the earliest start for the PCT horde in living memory. If the weather trends that characterized this Winter continue for another couple of months it is concievable that aggressive PCTers will start North in April.

Hell, you could start right now, and have real good chances that you will see less than two feet of snow along the Southern Sierra Crestline when you arrive at the Sierra.

Highly experienced backcountry travelers checked out for Winter travel and conditions could hike the length of the Sierra Crest in the current conditions.

January 6, 2012

We have been experiencing clear warm weather, and will for as far as the weather people can see. I'm looking for some superheated tropical moisture to blow up out of the tropics from the Southwest, sooner or later. I put the chances of big storms blowing across the Sierra out of the Southwest at 1 in 3.

During the ever increasing incidence of Winter being dominated by Southern Heat I have observed that big storms rolling out of the Central Pacific make up for the heat blocking the storms out of the Northwest one out of three times.

These storms are much different than the the cold storms blowing out of the Arctic. The Southern storms contain much more moisture, and at a much higher temp, than our traditional storms out of the Arctic.

This means that these storms can quickly deposit a huge amount of snow in the Sierra Nevada.


December 18

A big strong high is sitting over the whole Eastern Pacific and Western US that is anticipated to remain in place for at least the next six days. No rain, no snow, no "normal" weather.

November 25

Powerful weather  is sitting up in the Bearing Straight, but it is not being supercharged and swept down to the Western US by arctic chilling. A big high over the Western Pacific and Western US appears stronger than the cold low pressure zone around the arctic circle.

Oct 5

We'll see if these "early" series of storms out of the NW continues to grow through Fall, or if they just "turn-off," leaving us with yet another "Indian Summer" extending deep into November.

The fact is that there are no longer predictable seasonal changes in the face of the long trend towards very brief Winters and extra-long Summers that has been developing in the Sierra Nevada during the past 40 years.

The radical change to sub-tropical air flows beginning to completely dominate the N Pacific weather patterns, and across the NW US are productive of the freakish weather and unpredictable seasonal character that  have been expanding during the last 40 years.


The Arctic is losing its influence as the main generator of Sierra Winter weather. The only constant with our current weather pattern is that it is unstable and that the instability will continue.

To put it simply, we have fked the progression and character of the seasons up. Bad. And most of the people here on the West Coast are completely ignorant of the obvious and radical changes that have transpired during the past 40 years.

They were not here 40 years ago. They say, "It's always been like this."

Really? This perspective marks the practical failure of both our social and educational systems. Which indicts our failed political system... our ignorance has already radically changed our weather, and we are now far too stupid to even see the damage we have done.

Recent Past

The last two years have been "throwbacks," reminicent of the "old" weather pattern that began to seriously break-up during the late-70s. Traditional weather patterns no longer operate during the present time. In fact, the old "normal" weather patterns are now "abnormal." But the system kicks back into "normal" mode every now and again.

Last year we had the unusual combination of storms hitting the Sierra from both the North, out of the Arctic, and out of the South from the tropics. That is a rare combination, which brought a record snowpack deep into Summer.

Intelligent people have observed these radical changes in the character of our seasons and the radical changes from year to year with great concern...

The Long Trends

Prior to heavy snows of the last two years, which have both brought very late season Spring and very early Fall snows to the Sierra Nevada, we have been experiencing a 40 year long expansion of Summertime. This year Summertime is still batting a 1000. We still have a shot at the first year in my living memory experiencing an Endless Summer.

The overall trend for the last 40 years has been for Spring to begin earlier, and Summer to push deeper into Fall almost every year. Now Summer is looking like an all-year event.

This pattern has been so consistent it is now the new "normal." These last two years, as well as this Fall's early storms are bucking that long trend. Our mid-Fall pattern reverted back to being dominated by Southern and Western weather patterns.

Status of this Report

This is very much a work in progress... Keep tabs on the weather resources here, and look forward to impending Fall trail reports. Or post up your trail reports and observations about the character and progress of the deepening Fall conditions.


You can post up your notes and experiences with High Sierra Fall Trail Conditions on this page through the comments link below, or you can post up your own page about your trip in the Seasonal Reports Forum. Post up your experiences with these dustings of snow. Everyone freaks out... 

Oct 5: notes about various parts of the trail, see the Trails Forum.

Your reports on temps, weather, and trail conditions should be complimented by your trailhead, route, and dateson the trail. You gear selection and how your choices worked out are valuable bits of information.

I've set this page and its links up to arm you with the best information possible. If you have a resource you'd like to see here, let me know.

My Status

I'm still recovering from an injury, so you guys can add to our knowledge through the comments link below, or as your own article in this, the  Seasnonal Conditions Reports Forum.

But I've plans to sneak in my first trip this Fall before the snows fall. Stay Tuned!.

Done: Late October Fall 50 mile Scouting Trip: Carson-Iceberg Loop. Hole in toe held up well. Great rehab hike...

Feb, 2012: Recovery from frostbite (call me stubby) continues. Trying to put together the funds and fitness for 5th Tahoe to Whitney Hike this Summer...Still have a small hole in the tip of my shortened big toe...

Happy Trails,


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