BACKPACKER ALERT: April 1 thru August, 2017. PCT High Sierra Summer Threats EXPANDING

Alex Wierbinski's picture

By Alex Wierbinski - Posted on 01 April 2017




The Sierra Calendar draws together an extensive array of snow, runoff, weather, and temp information.

The Original April 1 Alert Below



Latest High Sierra Trail News


August 13


This Alert now stretches from the start of Spring across most of Summer, and I expected it would almost be expired by now, but its fundamental warning of Hazardous Snow Travel Conditions may well persist through the whole Summer.

Deep snow has finally retreated to highest and most protected perches in the North Sierra from the Tahoe Basin down to Raymond and Reynolds Peaks. Though we can still find plenty of snow in the South Sierra, we have to enter protected Northeastern aspects of the North Sierra to find substantial deposits and outcroppings along the Northern end of the Crest.

This continues through the thickening snow of the Carson Iceberg, until we find the Emigrant and North Yosemite still sporting a healthy layer of snow along the crestline.

Slick arms of snow across exposed trails on steep terrain crossing snow-covered ridges, or ridges harboring shealtered runs of snow are still an early morning issue, before softening sufficiently under rising sun for good traction.

Our high altitude Fords still appear much higher than normal for this time of year, still presenting a very late-spring type of flow conditions, still requiring a most carefully approached and well-thought fording strategy.

This Alert has retreated to the Sierra Crestline and its shealtered Northeast facing aspects.

Date-Adjustable High Sierra Snowpack Status

Amazing Sat Views of Sierra Snowpack  



August 3


A Vast Tropical Plume...

Weak Low a couple hundred miles off San Francisco is dragging a vast plume of tropical moisture Northwest, up across the whole length of S. CA & across S Arizona from Central Mexico.

8K Visible Western US

16k Water Vapor

It is a plume of fully moisture-charged TROPICAL AIR.

This plume is generating some serious electricity. Lightening & lightening-caused fires should be watched for and expected.

It's serious blowback from this interesting tropical weather trend/activity.


Lightening Probs


This current (visible) Sat View of West US shows the Low & its Plume to you, if you click it this morning.

This sat shows current conditions, so you will see what's up at the time you click it...


All Sat Views


Inspect the current hazard reports and the National Hazard Map:

High Sierra Hazard
National Hazard Map




August 2


T-Strom Warnings

Storm Warnings

Lightening Probabilities


Heavy snow at high altitudes mostly in the South Sierra preserves the:

but now mostly limited to higher up the flanks & crest of the South Sierra.

Still lots of snow on South Sierra & protected parts of North Sierra Crest, less on others.

Protected areas full of snow in N & S Sierra.

High Altitude Trips are STILL SNOW TRIPS

Date-Adjustable High Sierra Snowpack Status

Amazing Sat Views of Sierra Snowpack

Continuing high runoff flows maintain the

and must be monitored. Big Heat Building.

hazards are present & increasing.


Inciweb Fed



Dealing with Skeeters

Skeeter News & Info

Lightening Hazard

Water & Snow Hazards are gradually narrowing as this unique season progresses, while Heat, Fire, and Skeeter threats are HIGH & rapidly rising.

Trail News
August, 2017






July 31

Heat Hazard Rising

Heat Warnings in effect this week, building to Thursday peak.

Hazards in Effect

Heat Hazard

Fire Hazard

Smoke Hazard

Fording Hazard

Snow Travel Hazard
(High Elevations, mostly South Sierra.)

Exact Line of High Sierra Snow Cover



Fire & Smoke


Inciweb Fed



Check the Heat Intensity for Thursday.

Forecast Graphical Interface



July 27 

California Statewide Fire Summary

Over 5,000 firefighters are on the lines of 11 large wildfires burning in California.

High temperatures have returned to most of the state today. Many of the valleys and desert regions will experience triple digits today, as well as low humidity. These conditions are expected to remain through the weekend. 


Aporoaching the Late End of Snow
Snow is making it's final retreat up to high altitude and protected aspects, but is still requiring increased work and fording vigilance in the South Sierra. It has retreated off most the Northern Sierra Crestline, excepting protected positions.



July 25 


Fire Hazard, Detwiler & NINE other Fires

Smoke Hazard

Fording Hazard

Snow Travel Hazard (High Elevations)
See Exact Line of High Sierra Snow Cover


Fire & Smoke


Inciweb Fed


Check the Weather

Forecast Graphical Interface



July 21 

Heat Hazard Rising

Heat Warnings in effect this weekend

Fire Hazard, Detwiler Fire

Smoke Hazard

Fording Hazard

Snow Travel Hazard (High Elevations)
See Exact Line of High Sierra Snow Cover

Fire & Smoke


Inciweb Fed


Check the Heat Intensity for Sunday

Forecast Graphical Interface


July 20


Detwiler Fire

See latest trail news and below.


July 19 


Detwiler Fire

Smoke inundates Tahoe-Carson-Reno areas,
Lake Tahoe News, July 19, 2017.

All backpackers and visitors to the Sierra should check smoke and fire conditions. Smoke can be a real problem, even with no fire in near proximity.


Fire & Smoke


Inciweb Fed




Tropical Power Marching North 

A unique configuration of factors has formed up a "storm generation machine" (below) in the waters off of Central America for the past couple of weeks. A line of storms aimed at Hawaii have been deflected, swatted by the powerful, persistant High covering the NE Pacific.

Now these storms are marching far enough North that remnants of their massive moisture plumes could be swept East by prevailing winds across the Sierra during the next weeks.

This means that the chances of tropical thunderstorms and downpours are increasing.

Beware the Lightening

Best Sat View: IR SE Pacific




July 7

Continuing Hazards

Snow Travel Hazard: High Altitude Coverage

Fording Hazard: High trails flow like creeks, rivers are dangerous.



Heat Warnings and Hazards

Flood Warnings and Hazards from excessive thaw

Lightening Hazards


Graphical High Sierra Forecasts

Standard High Sierra Zone Forecasts

Lightening Probabilities



Heavy Lightening in South Sierra
July 7, 3:40 PM, 22:38 GMT

Special Weather Statement

On current radar
(22:38 GMT)

Lightening Forecasts




July 3

 Note that extended lengths of high altitude trails are still completely obscured by snow. You must be able to depend on previous experiences or navigational skills to maintain the proper route. Trails below the snowpack are running like creeks.

We've also seen backpackers stranded by rising waters in Bubbs Creek (article below), along that segment of the Rae Lakes Loop route. Previously, we got news that the Woods Crossing bridge was damaged and unpassable.
Nonetheless, stranding are indicative of continuing HIGH FLOWS through Sierra rivers and creeks presenting significant fording danger. 





Kaweah Commonwealth, July 3, 2017.

High Sierra Mountain Safety News




June 22


Heat Warnings expiring today-this afternoon.

SE Flank Flood Warnings expiring tomorrow:


Hot temps continue... just not at "Heat Wave" intensity. 


Heat Hazard still in effect

Fording Hazard still in effect

Snow travel Hazard still in effect


Risk Factors Rising

Fire & Smoke

Fire & Smoke Hazard Threats



Lightening Probabilities


Check the High Sierra Backpakers' Calendar


Surging Thaw

The Sierra snowpack is massive, and melting fast,
SF Crate, June 23, 2017.


High Sierra Snow Reporting Stations

High Sierra River Reports




June 21


The Threat Environment 

High Sierra Mountain Hazards


Special Circumstances





June 20



Bishop Creek Shuttle Operational
June 17

Sonora Pass Opens
June 14

All Trans-Sierra Highway Status News



Heat, Thaw, & Fording Warnings:

Hanford-San J
Potential Heat Risks Map


Heat Timeline
Sacto Valley & High Sierra



Mono Flooding Hazard Warning

Merced Flooding Outlook Warning




June 16

Heat Wave

Trail Conditions Report, June 16


Take note of
PCT hiker's recent self-rescue...

Snow thick and fords dangerous at altitude.




June 15
(updated 6-20)



Access Opening
Sonora Pass opening indicates that full access to the still deeply snow-covered Sierra Crest is beginning in earnest. Highway 108 across Sonora Pass will soon be complimented, or should I say, "bookended," by Highway 120 across Tuolumne Meadows to our South, as snowplows slowly approach Ebbetts Pass to our North. 

Soon the roads linking snow-covered sections of the Sierra Crest line will be open. This will open access to great lengths of the snow-covered Sierra Crest and its high flanks to great numbers of Summertime Backpackers.

Bishop Creek Shuttle Operational
June 17

Sonora Pass Opens
June 14

Wild Conditions
Yet the Sierra Crest is still holding ten feet of snow across even the lowest crest line passes. 

We have already passed May Day and are approaching the Fourth of July with a still substantial snow pack sitting on the Sierra Crest complimented by very heavy dangerous runoff flows still running steadily through Sierra Rivers and its Creeks, making fording incredibly dangerous. People have died, been injured, and been rescued.

The difficulities of soft snow and high rivers are multiplied by high heat.

These conditions are not going to be what many Summertime Backpackers expect, or are ready for. These are amazing conditions to observe and experience, but require more of everything. More clothes, more gear, more work, more food, more fitness, more navigation skills, and most especially, more common-sense and good decision-making skills. 

Time to exercise the skill sets?

Or time to exercise restraint?

Your life literally depends on the quality of each of your decisions.


Key Trips Made Easier by Opening of Highway 108

Climbing Leavitt Peak during Snow Conditions
(I prefer the hard snow of Winter...)

 Trail Guide Page

Kennedy Meadows Pack Station 

Let's examine the Sonora Pass region today, as it's just opened.

Sonora Pass
Background Information


Sonora Pass
ALL PCT & TYT Trailheads


History of Sonora Pass



Sonora Pass & Points East MAP


Sonora Pass & Points West MAP

Red dots on maps link to trail guide citations.


Sonora Pass, NORTH & SOUTH, and Both Flanks MAP

Black dots on map link to detailed maps. Red dots to the guide. 


What Time it IS
A wide range of fantastic snow trips North into the Carson Iceberg and South into the Emigrant Wilderness Areas are now possible out of the Hwy 108 corridor for expert three-season backpackers (must understand snow), who are well geared, and fit.

These are very difficult conditions. The April 1 through June Backpacker Alert is still in Full Force and Effect.








One AM morning precip hits Central Sierra, after a sloppy couple of days.

A very small amount of snow accumulation took place, followed by accelerated melting as majority of precip fell-falling as light rain.

"Sloppy" conditions next three days, and it looks like a day of snow in the North Sierra on Sunday.

This will intensify already difficult snow and fording conditions.

The Sierra Calendar draws together an extensive array of snow, runoff, weather, and temp information.

Original April 1 Alert Below

Latest High Sierra Trail News


 June 9

Huge Snowpack Remains, just higher up the flanks.

Dangerous River Flows increasing with precip bringing increased thawing




May 25

Original April 1 Alert Below


Latest High Sierra Trail News


May 25

Huge Snowpack Remains

Dangerous River Flows


May 25
Backpacker Alert Update

Memorial Day High Sierra Safety Warning
Deep Wet Snow & Surging Rivers & Fords


Memorial Day Opening Weekend Warnings
River and Terrain Dangers

General Hazards

Our first, most powerful and most widespread danger right now is in the water. This year's massive snow pack is thawing rapidly, with still a lot more to go, and these flows are already driving powerful river levels & flow rates bringing fording and drowning dangers to their highest levels.

The Spring Thaw has already claimed too many victims so far this year, and we are just now approaching the Memorial Day "opening" of this season. These events and the river's situation requires we all pay extra attention to ourselves and each other.

Combined Hazards
The approaching Memorial Day weekend traditionally marks the opening of the High Sierra Summer Backpacking Season, weather & trail conditions permitting. This year the massive snow pack decorating the Sierra Crest and way down its flanks are driving an incredibly powerful, dangerous Spring Thaw through the Sierra Rivers. Between the two of them, the overwhelming snow and its surging runoff, are serving up double-edged dangers touching almost all visitors to the Sierra Nevada.

The river flow dangers from the Spring Thaw in the High Sierra are not just restricted to the Sierra. The massive flows of these surging river courses in the High Sierra grow larger and larger the further down-mountain they flow, picking up vast amounts of surging runoff all the way down through the flanks, the foothills, until they surge into the San Joaquin Valley as very dangerous flows.

Every elevation of the rivers coming down off the Sierra Crest are currently dangerous.

 River fording dangers are not restricted to backpackers high in the Sierra. The opposite is true, in fact. Most of the fatalities so far this year have been "civilians," city folk unaware of the danger zone they had entered upon approaching a Spring Thaw surging High Sierra river.

The bottom line is that ALL rivers and even the currently surging creeks should be approached as a potential deadly danger, the risks and dangers properly identified, then respected properly.

The brutal flow rate, big rocks, and biting cold rapidly finish off anyone accidently or inattentively stumbling into the rivers.


Backpacker Specific Hazards
Snow Hazard

A typical High Sierra backpacking route will cross a river valley, climb to the Pass, then drop down into the next river valley. At this point in time the fords in the river valleys will be surging, and potentially not crossable. The climb up to the Pass and back down to the next river valley will be covered by up to 12 feet of snow. This snow is special. It is Spring Snow that has lived a long time.

High Sierra Snow Reporting Stations

High Sierra Backpackers at this point in time will specifically face deep, wet, soft, snow that will saturate all body parts & gear bits in contact with it. It will offer little support. It will suck you in with each step.
This process of getting saturated in soft snow typically involves taking one step and plunging in up to your waist, then another. Repeat. Backpacking across soft, wet snow is physically exhausting, as well as being cold and wet.

Thus the Spring Backpacker in conditions we face today must understand the consequences of getting wet in these unique saturated-snow conditions. These conditions require all who enter them have the fitness, gear, and skills to stay warm overnight while wet after "X" number of exhausting days of work.

Once we hike to the Pass and back down to the river valley we are going to be facing some downright dangerous fording conditions at the current time.

Fording Hazard
The main fords in the river valleys between descending Sierra Ridges are going to be at or near their heaviest historic flow levels and present real challenges and dangers to even the most experienced and strongest backpackers. Many will not be crossable.


High Sierra River Reports


Latest High Sierra Trail News


 May 15

All recent warnings below and the original April 1 Backpacker Alert below are both still in full force. The dangers are in fact increasing with the steady increases of temps, melting, and subsequent rising river flows.

We're just getting started, in a manner of speaking.

Currently we're watching a weak Low tracking around the Northeast edge of the Vast High off the coast of Ca (Calendar May 12-current date) which may be dragging a Cold Front from NW to SE across the Sierra this upcoming week. 


What I call,

"a little Spring Spinner." 


Cold & Wet Warning
For Hikers this sloppy weather means tough hiking in soft, wet snow with surging fords if high elevation showers scour the snowpack.  Clearing later this week after Low passes can bring low temps while wet: Cold & Wet Warning.

Be Ready, Freddie...



Weather and Conditions


High Sierra Weather Page




All High Sierra Snow and River Flow Status Information



May 5


 > Very Difficult High Sierra Travel Conditions <


1> High River Flows claiming lives. Fording Dangers Increasing.

2> Avalanches happening, and claiming lives. Snow pack coming apart.

3> Mosquito populations swelling and moving up-mountain with thaw.

4> Weather; light showers across Sierra Crest for next couple of days.

Latest Trail News



May 2

Sierra Snow Pack 195% of May 2 Average, two fatalities reported April 24.




 April 20

Snowpack officially Vast:

April 20 reading puts state average near 200%
(See Calendar)




April 19

This Alert will be in effect as long as this massive snowpack sits upon the Crest. That is uncertain, but will likely last through at least the middle of July, depending on weather. Good chance for this snowpack to see next season's Winter.

4-20 Weather Status Update

April 19 Weather Status Update

See updates through comments below, and the
2017 High Sierra Backpacker's Calendar.







April 1, 2017
The most important topic of this date is the massive snowpack on the Sierra Crest and the extreme danger it poses to PCT hikers. The dangers of High Altitude Snow Travel will soon be supplemented by very dangerous fording conditions when this snowpack begins to thaw.

These conditions require skills, gear, and fitness to assure any level of safe travel as of this date. Undercutting and safety along the banks of creeks emerging from snow cover is currently increasing, as will the difficulty of travel conditions increase as the pack softens under the increasing heat of Spring.

Extremely difficult travel conditions will soon shift from hard snow that defies traction to wet snow offering no foundation. We will shortly transition from barely clinging to the mountain-side to sinking up to our waists with each step. As Spring progresses cold mornings will bring the former condition, warm afternoons the latter.

The same temp shift driving the changing character of the snow pack will soon drive even the highest river fords to levels unsafe for fording, and make the major rivers raging torrents of destruction. These temp shifts change the character of the Sierra.

The snowpack itself will become sopping wet, saturating anything and anyone in contact with it. These are the times that hikers without sufficient insulation can find cold combining with exhaustion to degrade decision making as well as technical execution & style to create very dangerous situations. I see Wet, cold, and tired PCT hikers surrounded by a sea of deep, wet, energy-sucking snow divided by an endless series of raging torrents of typically tiny High Sierra creeks surging like rivers, each supercharged by Spring's mighty flows.

The trails will be flowing like creeks, when we get down to them. And they will lead to the mighty rivers, which will be downright scary, once this massive snow pack begins to melt in earnest.


On March 25th Cayenne added her observations about this Spring,

"I just checked their site (PCT) and no mention or discussion about the fact that the PCT will not be 100% open this summer. Mammoth, last summer was a shit show of backpackers between the PCT and the JMT. People are planning their trips now with no clue and all “positive vibes & intentions”.

For example, during the 2011 (heavy snow) summer we planned to camp in the meadow (Tuolumne) and ended up camping in Lundy Canyon instead. Did the hike up to Lundy Falls in ankle deep water, the trail was a creek. That is what I expect for this year in the Sierra’s.
I did not even go into how many down trees, eroded trails and washed out bridges will be encountered. Not a good year for the novice backpacker or hiker. Can anybody say, “backcountry glissading accident or swift water rescue?”

Dude, we had 180 mile ridge gust out here – INSANE!!! The cornices on some of the high altitude passes will not melt out on the north facing aspects this summer. NOAA is calling for over a foot of snow this weekend. The high country just keeps getting hit.

I am happy the drought is over and the CA & NV water table will be refreshed. I hate fording rushing creeks in waist deep water and big rivers freak me out.

I honestly think that very few people will complete the PCT this year because the Cascades have had an amazing amount of snow too. Crater Lake, Mt. Bachelor, Mt. Hood and Mt. Baker are all having record snow years too. We lived up there from 2000 – 2006 and drifts take a long time to melt out up there in record snow years.

I will do my best to keep people informed as “The Great 2017 Thaw” begins!


Me too!

Take Care and Bee Safe


Happy Trails,



Spring Thaw Conditions

Calendared Status with Reporting Resources

Week of April 9 to 15

Week of April 16 to 22

Week of April 23 to 22


Latest News/Status

Latest (April 1) Snow Course Measurement

All Snow & Thaw info on Weather Page



All Snow Reporting Stations and Watersheds

All River Flow Data, Forecasts, & Warnings


PCT Hiker Snow Accident & Conditions Report,
Whiteblaze, March 24, 2017.

High Sierra Mountain Safety: Wrecks & Rescues



Latest High Sierra Trail News


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Alex Wierbinski's picture

Snowpack officially Vast:

April 20 reading puts state average near 200%,

Alex Wierbinski
Alex Wierbinski's picture

REPORT Kennedy Meadows Pack Station

Report from Matt Bloom of Kennedy Meadows Pack Station.

"PCT hikers in the snow for a long ways & time this year."

"KM will be Opening for Trout Season on APRIL 28, come on up."

Sonora Pass: "It looks like Sonora Pass will open between Memorial Day Weekend and Mid-June, is my guess right now, but this depends on weather."

This will be a slow Summer in the mountains and a short season for the High Country."

Make your time count!

Alex Wierbinski
Alex Wierbinski's picture
April 19th

Note the pattern of a series of Highs & Lows I mentioned on the 15th has sustained itself through the 19th, & looks likely to contain one more wet pulse.

Look at the pattern of that week swinging from Storm to Cold warning and back to Storm again as each pulse of High and Low pressure came across during the week of April 9-15:

From the 6th to the 20th we've seen a remarkable pattern composed of a rapid series of Wet, Warm frontal-Lows followed by brief clear, cold Highs. Rapidly. This current cool High is giving way to another frontal Low, & it will warm into the 20th with that moisture as this pattern then breaks, followed by cooling with the clearing-High building from 21st to 24th.

Then, after the 21st some heat will build in under a more persistent High, unless this series of Highs-Lows come back...

This means a nice window may well be opening up for some deep-snow High Sierra Snow Trips this weekend and next week.

Maybe. This is classic Spring Instability. Keep your eyes open, and on the skies! The weather plays the tune and sets the timing the snow melts by.

Alex Wierbinski
Alex Wierbinski's picture

This snow travel hazard was quickly compounded by mountain storm warnings from the sixth to today, the eighth. The decay of this storm is opening some clear skies and the potential for a COLD HAZARD CONDITION this evening, the eighth of April.

This cool little High forming over us now appears to be followed by a mass of tropical moisture moving our way. It appears that the period of low precip stability we experienced during the month of March and beginning of April is over.

The question is how it will heat up, for heat up it will. Will it heat up rapidly, lashed by continuous tropical storms? Or will it heat up slowly under diminishing cold snows?

That question determines a whole lot more than just the fate of our backpacking season. The short term answer this year determines the stresses the whole California Water System will face this year. The very viability of California's water system and the vast population it supports, and maybe even the fate of Mankind hangs in the long term answer to this same question.

Alex Wierbinski
Alex Wierbinski's picture

Peter checks in on April One after retiring the Lake of the Sky Outfitters in South Lake Tahoe. Peter brings the wise observation that the skeeter populations are going to be huge and likely fed by moisture all Summer long.

Alex Wierbinski
Alex Wierbinski's picture

Marty Maine, Senior Trail Crew Mechanic, reported on April 1 that numerous hikers are starting out too early for their skill sets.

Marty reports that 3600 PCT permits were issued, and both he and Cayenne below are concerned not just about safety issues of hikers unprepared for extreme snow and fording conditions, but also about congestion on trail and especially at resupply spots as countless disappointed PCT hikers are driven off the trail.

Marty and others concerned in & with backpacking the Sierra have been heading South this Spring to bring good scouting information to potentially thousands of minally or under-informed and under-geared PCT hikers who are currently hiking North.

This is not an "ultralight" Spring in any sense of the word!

Alex Wierbinski

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