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High Sierra Spring of 2018 | High Sierra Backpacker

High Sierra Spring of 2018

Alex Wierbinski's picture

By Alex Wierbinski - Posted on 14 June 2018

High Sierra Spring of 2018
Evolution of Conditions

Page Started
March 20, 2018

Tracking the Spring Thaw of 2019


Fall 2017
Setting the Scene for the Winter of 2018



June 7, 2018
Calendar Entry:

High Sierra Travel Status


Spring Travel Warning
Still in Effect

Summer Conditions approach, yet conditions on the ground are still in Spring Snow Mode.

Snow/Hard Snow Surfaces early in the day:
Slip & Slide Traction Dangers
Difficulty of Post-Holing when Warmed-up, Soft & Wet, later in the day.

Shaded areas and NE aspects have extensive snofields which are slick and hard early, then wet & deep later in the day.


High Fording Dangers

T-Storm & Lightening

In addition to the travel hazards on land, it can still get cold and wet in the sky instantly, as is always the case in the Sierra, even during Summertime. During Spring, conditions can shift to very cold and very wet very quickly.
The next danger after getting soaking wet while hiking through this warm, wet snow is suffering and freezing at night. Shoes, pants, socks, and everything else that touches a wet snowpack gets wet. Later, during the evening, the wet clothes will become very cold.
Thus, Extra and Proper Clothing Layers that can allow us to recover our warmth, and keep us comfortable, if not dry, in wet conditions, are still required.

I can't count the times during Spring and Fall I've been in wet tents, in wet clothes, in wet and snowy-cold conditions (the friggging worse) counting my blessings that, despite my misery, my clothes, tent, and sleeping pad insulation from the wet snow were keeping me warm, after I had exhausted myself postholing through a slurry of snow and rain was falling on the deep, wet, grasping snowpack.

Just getting warm has always been enough to charge my wet batteries.

Thus the "Spring" Gear should still be in the pack, though our "Spring" gear can be little more than our Summer gear, with these required extra layers for the proper level of safety for travel through the slick and the sloppy phases of a diminishing Spring snow pack.

Our gear should still be tailored to keep us warm while wet in snow.

The next heat wave should leave little more than snow remnants along the Sierra Crest.




May 22


Mammoth to Stay Open to Mid-June

What does this Mean for Snow-free Trail Opening?




May 17

"Sloppy" weather brought by a Low East of the Sierra has brought thunderstorms, clouds spitting rain below about 8000 feet, with dustings of snow above. Though not too cold, this kind of wind-driven wettness can induce hypothermia if we don't have the ability to stay warm when wet. Good insulation is mandatory!

Difficult travel conditions through the diminishing snowpack continues, fording dangers are high and increasing. One good heat wave will clear much of the Crest Trails of snow while flushing the majority of the thaw down mountain. On the other hand, cool temps and moist cloud coverage could draw-out this Spring Thaw's period of difficult snow travel and dangerous fording conditons but a little longer than a heat wave could clear them. That's because the snow pack is thin, and does not have much of a future in either case. Let's take a look through two lens:



Regional Snow Analysis
Set Date


Clear trails will come early this year, exactly how early depends on how the next couple of week's temps and weather play out.


High Sierra Highways


Sonora & Ebbetts Passes Opened 1st Week of May




Two Reports in Mountain Safety Section

Two Fatalities in Sequioa, Body of Lost Skier Found in Tahoe

 "Hikers and climbers are cautioned that winter conditions still exist at higher elevations, and extreme caution is necessary."


Bottom Line

Spring Temp & Snow conditions are operative in the Sierra Nevada now, with increased fording danger. A heat wave will increase the fording danger. Spring Snow Gear is still required for safe mountain travel in the Sierra.

Summer-PCT lightweight gear WILL NOT CUT IT. Don't even try...

April 25: Winter to Spring Gear




May 8


May 2018
May 2018 Compared to the last three years.

May 8, 2018
All Trans-Sierra Highways except the Tioga Road are OPEN, and 120 should open shortly.




Review May 2017 against May 2016




A Deluge of wet and sloppy weather, rain, hail, snow and lightening begins.
The beginning of a sloppy Summer of 2015.

Earliest Opening of Roads and Trails in History?


2% of Average Snowpack

55% of Average Snowpack

194% of Average Snowpack

37% of Average Snowpack


27% of Average Snowpack



 April 25



It's getting time to thin out our Winter Gear with the lighter bits we can utilize along with the rising temperatures of Spring. But we've got to be careful!

It looks to me like the Winter Mountain Jacket can retire for the season, being replaced by the medium-weight shell. Sub-Zero Winter bags can be traded in for a Zero-degree bag, depending on forecasts and current conditions.

Switching out the heavy shell and sleeping gear brings increased risks, so I typically keep my Winter layers and insulation in the pack until the temps rise a bit more. My approach is to figure out how warm I can be in my tent, in my sleeping bag, wearing all my gear against what I figure is the worse-case weather goes bad scenairo.

Though I feel comfortable lightening up the jacket and bag at this point in this season, with these temps and conditions, I still want to keep my Winter insulation layers as back-up insurance, in case the weather takes an unexpected turn for the worse.


Trail Guide

Calendar: Recent Temps & Snow


Watersheds and Selected Network of Crestline Sensors



Trail Guide

Four Season Backpacking Gear List




April 19

 This Week
High Sierra Backpacker's Calendar


Tuolumne Meadows Winter Rangers

Reporting Bear Activity & Dangerous Fording Conditions at TM Elevation:

Update for April 18, 2018 (last update for the season),
National Park Service, TM Winter Rangers, April 18, 2018.

April 19 Weather Note

On the 17th we observed a Low coming out of the Northwest towards N Cal & the Sierra. This Low traveled down the Ca Coast on the 18th, not turning East until it approached LA, completely missing the West flank of the Sierra from the West.

On the 19th it passed around the South end of the Sierra in a Northeastern direction into  central-South Nevada, from where it brought snow flurries to the Sierra from the East.

This low has now passed to the East over the Central US. 

High Sierra Calendar: Week of the 15th to 21st.




April 16

A Tropical April, So Far...


Tropical Times, Radically Changing Mountain Weather

No Snow But Over Two Inches Of Rain In Tuolumne Meadows



April 13


Recent Record Rainfall

April 7-8 Tropical Transport Mechanisms


High Sierra Calendar, April 15-21, 2018



March 25
Season So Far

March 2017
At the beginning of March we were looking at 20% normal snowpack, one of the historically most signiifcant low snowpacks in an era of historically low snowpacks. Now, approaching the end of March we are breaking or nearing the 50% line.

November 2017
The end of last Summer was baking, bringing heattwaves and megafires to Northern and burning South California in December! After that extreme heat we got the most Fall snowfall through the month of November since the '80's.  Then, after that, the faucet turned-off, and we were at historic snowpack lows at the beginning of March. Very low.

We had about the same snowpack in early March we had in late December,

The faucet turned back on in late Feburary and March. This is not normal weather we have been experiencing through last Fall & across this Winter, nor has the weather been "normal,"  or operating within its "normal" ranges for quite some time. The weather is highly unstable far outside its normal bounds. This abnormal weather took something abnormal to knock "it straight."

The Blocking Ridge
This Winter we watched a series of vast blocking ridges, which I directly attribute to our radically changing seasons, which I directly attribute to our over-development and over-populating California, covered the Northwest corner of the US from November through March, bringing a record-level lack of snowpack.

This blocking ridge pattern stood-up and persisted, until it was broken-up and "warped" by another, even stranger and more powerful freak atmospheric affect of global warming.

The effects of our changing climate are crashing into each other, and in our case the Winter drought "ridging" effect was displaced by a global-warming inspired breakdown in Arctic weather. Ironically, the currently damaged warm and weak status of the Polar Vortex every Winter is (from my perspective), a major contributor to the conditions allowing the persistent ridge to persist off the Western Coast of the USA...anyway...

Broke the Blocking Ridge
The extreme heating of the Arctic Circle and extreme weakening of the real Polar Vortex during this year's Northern Hemispheric mid-Winter split the alreadly weakened Polar Vortex, specifically, the extreme warming in the Arctic and its stratosphere this year actually split the Polar Vortex in two, sending two spinning vortices reeling Southward off the top of our planet.

Polar Vortex Splits Under Warming Stratosphere

The result here on the West Coast of the USA was that a huge Cold Low moved to the Southwest from the highest Arcitc across Northern Canada, a Low who's cyclonic roataton (counter-clockwise), swept a vast flow of superchilled mositure (super cold for us down here, but temps that were crazy warm for the Arctic...), down the Western Coast of the United States.

That disruption disrupted the persistent ridge off the West Coast of the USA.

The chaotic result  was that the climate-warming splitting of the Polar Vortex had the effect of breaking-up the persistant HIgh, which is itself a product of global-warming changes to the local, regional, and tropical heating patterns, one that was (and is) setting-up and creating yet another super-drought Winter on the West Coast of the US.

Now that's over: The superheating of the Arctic split the Polar Vortex, and one of the vortices spun down this way, its cold air disruptions breaking the persistent ridge that was establishing drought conditions on the West Coast;
This breakdown is what paved the way for last week's tropical torrential downpours to sweep across the Sierra and most put some tropical moisture on most of the Western United States.
These kinds of dry seasons, with dry weather puncuated by tropical downpours, is not California's traditional weather, for those that don't know... but it's a big part of the new weather pattern marching relentlessly North across us.



Right now a big High is moving Southeast and looks like it's building in over the West Coast of the US. The Spring Thaw begins Right Now, If that High just sits there, if it reasserts the persistence and heat of the previous Highs that have come to characterize and dominate Northeast Pacific Ocean Winter Weather Patterns.

Winter is done if that High goes stationary, and it sits over the West Coast for the next week (or more), heats up, and begins deflecting Arctic moisture around its NE flank while deflecting Tropical moisture around its SE flank, creating a rain shadow of warmth that the High Sierra basks in, in the eddy of this kind of HIgh.

Or, maybe not. The other option is that this High moves East, East with the relentless Eastward flow of our spinning atmosphere on our spinning planet. Is this next High one in the never-ending relentless cycle of Highs and Lows? Or will it establish itself and stay a while?

Will it stay or will it go?


The answer to that question determines exactly how the trajectory of this year's Spring Thaw begins. It was "kind-of" answered when tropical rains swept the Sierra Crest this week. I see that, tropical rains across the Sierra Crest, as a very bad omen for enduring Winter conditions, an omen of a rapidly approaching Thaw.
In either case this next High is either the first harbinger of the first stirrings of the Spring Thaw this year, or it is only a short break between what would be an even more surprising series of late-season "savior" snow storms and snow depositions than we've already seen this March.




The viability of hoped-for very early starts for long distance High Sierra PCT-TYT-JMT backpacking trips are being determined in the atmosphere and on the ground right now with the approch of this vast High...



Favorite Surface Map Animation: North Pacific

Map Now


All Onland Surface Mappage



March 21



Powerful flows of warm tropical moisture are moving rapidly out of the Southwest from a lattitude equal to Hawaii, and are now pushing high temps and rain up to high elevations along the Western flank of the Sierra, even up to, and even occasionally washing across the crest.

It looks like a lot of rain is falling on a lot of the snowpack down low and up high.



First Day
Spring of 2018

March 20

Vernal Equinox
First Day of Spring

09:15 AM PDT

Equal Length
Day & Night:
March 17
Sunrise Sunset
March Calendar

Time & Date





Seasonal Animations & Tools






Percent of Average for
March 20
+/- change since
March 14

N Sierra: 40%

Cen. Sierra: 55%

S Sierra: 43%

Ca State: 48%

March 14, 2018
March 5, 2018
March 1, 2018
Feb 24, 2018

Statewide Summary of Snow Water Content PDF


High Sierra Calendar
This Week in the High Sierra


We're starting Spring with potentially torrential rains, tropical downpours, from a warm Tropical Transport Mechanism, AKA, "Pineapple Express," arriving today. These Southern Lows dragging warm, tropical Fronts we are seeing today are looking to be followed by Lows out of the Northwest, dragging Cold Fronts down from the North by midweek.

As our Weather West analysis indicates, the first tropical Fronts may bring rain all the way up to 10,000 feet in the Southern Sierra!

Tropical Transport Mechanism Targets So California

Interestingly, it's looking like one of the Lows currently off the coast of central California will wander North, then come back South dragging a Cold Front from the North. We saw the same behavior earlier this month.

Seasonal Turnaround?
What this means is that the near-record low snowpack pushed all the way up to February 17, when the super-warmed Arctic split its Polar Vortex, sending one our way. The split Polar Vortex disrupted Northern Hemisphereic weather, in our case breaking the persistent ridge sitting like a wall along the California Coast, until then.

Spring Begins with Less than Half Normal Snow
The first two weeks after the Polar Vortex split brought cold temps, then the next two weeks has brought a slow build of the snowpack, back up to approaching 40% of normal, before the Fronts impacting today.

Trail Sense
What was looking to be a very early opening and start of this Spring's hiking season has been pushed back towards more normal dates by these current storms. We'll see. Things change rapidly in the Sierra Nevada Mountains.



2018 High Sierra Backpacker News





High Sierra Spring of 2018 weather trends temps thaw snow river conditions


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