The Character and Evolution of the High Sierra Winter into the Spring of 2019

Alex Wierbinski's picture

By Alex Wierbinski - Posted on 02 February 2019



Almost Dead-Average Snowpack

February 2, 2019
The salient point today, the second of February, is we’ve got a seasonal normal, “average,” snow pack (calendar), while looking at a set of moderately powerful storms coming through, all playing out in the wake of the disruptions created by the great movement of the Polar Vortex, off the top of the planet to center its spin over the North end of Hudson’s Bay, over the past couple of weeks.

Today we can see the Polar Vortex has split into thee, "vortexes," with the one over Hudson's Bay, the one that brought so much frigid Arctic cold air to the South, has weakened in favor of the Vortex to its North:


High Altitude View of the Polar Vortex(es)

10 hPa, roughly 84,998.2 feet of elevation.

A rough table of pressures and altitudes.


Where does, “it,” our Seasonal Transition into Spring, go from, “here?”

First, let’s establish where, “here,” is, and how we got here. Will the extremes we've experienced over the past six months continue over the next six? Let's try to figure out our range of future potentials, whichever way it actually goes...


Quick History of Fall of 2018
into the
Winter of 2019


Summer-Fall 2018
Setting the Table for the Winter of 2019

Fires started early and fiercely during the Summer of 2018,
following the 58% water year of 2018. Last year’s weak snow was preserved late into the Spring of 2019 by cool air transported down here by last year’s Polar Vortex.
All % below are the Average Snopack for that date.


Early July, 2018

Yosemite Foothills

July 2018 Backpacking Calendar

Tracking Page



September 8, 2018
September-October, & (November!) 2018 California Fires
Donnell Fire


Oct 2
Brief Downpours, Calendar


November 9, 2018


Storms of Nov 21 & 29
While Bringing Season Normal Ave Snowpack: More South, Less North, to create a normal year. Calendar


Nov 25
(by weather & work!)


December 5, Calendar

December 31, 2019



Jan, 10
Storms of Early Jan, Calender


Jan 13
<Polar Vortex Forecasts>


Jan 14-18 Calendar

Jan 31, 2019
100%, with storms coming through, Calendar

At this point in time, this year’s prospective PCT & JMT hikers should have no illusions about an early entrance & crossing of the Sierra Nevada, and are adjusting the timing of the start-dates of their ventures accordingly.
But, today’s conditions are not the, “last word,” on when the High trails will be accessible to Summertime backpackers. The coming trajectory of the end of Winter and arrival of Spring will finally determine every backpacker’s start dates, which also depends on your particular levels of skills, fitness, and gear use.

Skills Access
Those with the highest degrees of skills, fitness, and gear can exercise year-round access into the Sierra, and even the, “average,” prospective PCT-JMT hiker who possesses, “Summertime,” backpacking skills, is going to be required to develop excellent snow and fording skills, if you hope to enter and pass safely through the Sierra during any part of the Spring Thaw, independent of when it actually happens.

Peak Thaw
I highly suggest avoiding the period of peak Spring Thaw runoff flows through the rivers and big creeks, as they have periods when they are impassable during normal or heavy snow years.

Into the Spring of 2019
Into The Theater of All Possibilities
Conditions can change rapidly. A big blocking High and heatwave can rapidly re-tailor the snowpack. Or, a Tropical Transport Mechanism could throw another ten feet of fresh powder on top of today’s season-normal snowpack. That same TTM could also convey the vast amounts of tropical heat and moisture necessary to scour the snow off the Sierra with tropical downpours, depending on the route it takes to get here.

Those three extremes would be the, “bookends,” on the, “bookshelf,” of our potential seasonal-evolution possibilities.
To complete the range of possibilities we face, we’ve got to add the possibility of a, “normal,” average Winter snowpack transitioning into a,”normal,” average, Spring Thaw, right in the middle, between and balancing the extremes of Hot, Wet, or Snowy seasonal transitions, and their various combinations, any of which we could experience between here and the dry trails of Summer...

We sit in The Theater of All Possibilities, watching to see which one unfolds. Which one?

That’s the question everyone is hoping and/or betting on!

Extreme Times
The increasing incidence of, "extreme," weather events advises me not to be surprised at exteme weather of any type, over the remainder of this Winter and the length of Spring into Summer.


Earlier Observations

January 17, 2019


January 13, 2019
Polar Vortex Splits Under Warming Stratosphere


Status of High Sierra, October 16, 2018


Feb 2018
Last Year’s Polar Vortex




Feb 2019 Trails, Weather, Terrain Forum

Feb 2019 Trail News





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character, weather, seasons, summer, fall, 2018, winter, spring, 2019, High Sierra, California, weather information for prospective Pacific Crest Trail and John Muir Trail hikers looking for an early start


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