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Sept. weather on the JMT

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  • dbindsch@rocketmail.com
    I m planning to hike the JMT beginning on Sept. 4th. So one of my concerns has been having the appropriate gear for September temps. Particularly because I ve
    Message 1 of 19 , Jul 24, 2014
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      I'm planning to hike the JMT beginning on Sept. 4th. So one of my concerns has been having the appropriate gear for September temps. Particularly because I've focused on lightweight backpacking the past couple of years. So I'm looking to keep my base wt down in the 10-12 lb range, which means careful choices about (especially) sleeping gear and clothing.

      So I've followed the lead of several of the long-time members here (particularly John Ladd) and done an analysis of temps from 8/24 - 10/7 for 2009-2013. The spreadsheet and plots are in the Files area under "Weather" so anyone can take a look and draw their own conclusions. The data are from the CDEC website (see the spreadsheet for details) and are from the Bishop Pass Station, which is one of the few at 10,000 ft or above (it's at 11,200)

      My conclusions are as follows:

      - Temps in Sept show a general downward trend of a few degrees per week. However, the variability at the low end seems to increase significantly in the latter half of the month (at least for the 5 previous years). In other words, its much more likely to experience a suddenly, significantly colder  night or two in the latter part of Sept.

      - For elevations at 11K or so, there is a reasonable likelihood of temps dipping into the 20's at night, but it's not common. Temps below 25 degrees only occur 10% of the time in Sept. Temps below 20 degrees only. Note that the dry adiabatic lapse rate is ~5.5 deg per 1000 feet, so camping at (say) 9000ft one would expect to be roughly 10 deg warmer than at 11K feet.

      - Since I'll be at the highest elevations nearer the end of the month, I should be prepared for temps down in the 20s, or expect to spend at least one to three nights shivering. I also got some great feedback from folks over on Backpackinglight's website, indicating that it's wise to be prepared for nasty weather to accompany a cold snap.

      For anyone interested, my gear list can be found at this link


    • straw_marmot
      When estimating the expected temperature at a different altitude, you re concerned with the atmospheric (aka environmental) lapse rate, averaging about -3.5 F
      Message 2 of 19 , Jul 24, 2014
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        When estimating the expected temperature at a different altitude, you're concerned with the atmospheric (aka environmental) lapse rate, averaging about -3.5 F per 1000ft.

        (The adiabatic lapse rate is the temperature change of a "parcel" of air that moves quickly up or down without exchanging heat with the surrounding air, not relevant to what you're concerned with here.)
      • Calley Ordoyne
        Thanks for this analysis - I m also planning to be on the JMT in mid-September, so I m wondering if you can briefly summarize what you mean by nasty weather
        Message 3 of 19 , Jul 25, 2014
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          Thanks for this analysis - I'm also planning to be on the JMT in mid-September, so I'm wondering if you can briefly summarize what you mean by "nasty weather" accompanying a cold snap? Afternoon storms, or something else?

          Thanks!
          Calley
        • Turk6177
          Great info. Thank you. What happened to the 2012 data? Was it really -22 as the low for all those nights? That seems like quite an anomaly. Sent from my
          Message 4 of 19 , Jul 25, 2014
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            Great info. Thank you. What happened to the 2012 data?  Was it really -22 as the low for all those nights? That seems like quite an anomaly. 

            Sent from my Fantastic iPhone 5!

            On Jul 24, 2014, at 21:59, "dbindsch@... [johnmuirtrail]" <johnmuirtrail@yahoogroups.com> wrote:

             

            I'm planning to hike the JMT beginning on Sept. 4th. So one of my concerns has been having the appropriate gear for September temps. Particularly because I've focused on lightweight backpacking the past couple of years. So I'm looking to keep my base wt down in the 10-12 lb range, which means careful choices about (especially) sleeping gear and clothing.

            So I've followed the lead of several of the long-time members here (particularly John Ladd) and done an analysis of temps from 8/24 - 10/7 for 2009-2013. The spreadsheet and plots are in the Files area under "Weather" so anyone can take a look and draw their own conclusions. The data are from the CDEC website (see the spreadsheet for details) and are from the Bishop Pass Station, which is one of the few at 10,000 ft or above (it's at 11,200)

            My conclusions are as follows:

            - Temps in Sept show a general downward trend of a few degrees per week. However, the variability at the low end seems to increase significantly in the latter half of the month (at least for the 5 previous years). In other words, its much more likely to experience a suddenly, significantly colder  night or two in the latter part of Sept.

            - For elevations at 11K or so, there is a reasonable likelihood of temps dipping into the 20's at night, but it's not common. Temps below 25 degrees only occur 10% of the time in Sept. Temps below 20 degrees only. Note that the dry adiabatic lapse rate is ~5.5 deg per 1000 feet, so camping at (say) 9000ft one would expect to be roughly 10 deg warmer than at 11K feet.

            - Since I'll be at the highest elevations nearer the end of the month, I should be prepared for temps down in the 20s, or expect to spend at least one to three nights shivering. I also got some great feedback from folks over on Backpackinglight's website, indicating that it's wise to be prepared for nasty weather to accompany a cold snap.

            For anyone interested, my gear list can be found at this link


          • ravi_jmt2013
            I completed the JMT on September 14 last year and the lows never got to the point where my water bottles froze, except ascending Mt Whitney early on the
            Message 5 of 19 , Jul 25, 2014
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              I completed the JMT on September 14 last year and the lows never got to the point where my water bottles froze, except ascending Mt Whitney early on the morning of the final day.  I was never uncomfortably cold except on Mt. Whitney. My guess is that a 20 degree quilt might be less than totally comfortable at the end of September toward the southern half of the trail except for warm sleepers. I had a 15 degree Marmot Helium on the JMT which keeps me warm into the mid 20s plus I had down socks. I've had much colder nights on the Appalachian Train in mid-late April than on the JMT in the first half of September, including a few nights where my water bottles froze almost completely.  
            • John Ladd
              The error rate at these automated Sierra weather stations is high. At any of the stations, you see apparent errors, usually sudden downward spikes that are not
              Message 6 of 19 , Jul 25, 2014
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                The error rate at these automated Sierra weather stations is high. At any of the stations, you see apparent errors, usually sudden downward spikes that are not also reflected at nearby stations. Or protracted spells where the station gives the identical reading over an unrealistically long time frame.

                My approach has been to look at two nearby stations - Bishop Pass and Volcanic Knob and consider it a true reading only when both stations show a cold night. What I've seen is very similar to the original poster. Nights down to the mid-20's can be experienced in any month along the JMT, but become more common in September with first snow usually in late September or very early October. First snows are generally light enough to create only fairly minimal navigation and hiking problem on the following day.

                Emphasis on all of this should be on the "generally" part. Sierra weather is highly variable and very local. On a 20 day Sierra hike it is usual to run into at least some unusual weather. If you are lucky, the bad weather happens in the next drainage over, but it may happen in the drainage where you happen to be at the time. 

                I usually -- and almost always in September -- throw a SOL emergency (PopTart style) bivy into my pack for the unusual cold snap. I've never used it but I find it comforting. I also take it with me on sidetrips where I don't want to carry a full pack but want something to help me survive the night if I have a fall and press my 911 button on the Spot.


                For me, the added comfort of a lighter pack is not worth giving up protections like the emergency bivy. Others will, of course, differ in this tradeoff.

                I'd also add that heading a bit uphill can sometimes help as cold air often pools in the lake basins that many people prefer for campsites. A climb of a hundred feet in elevation can give you a warmer location.

                John Curran Ladd
                1616 Castro Street
                San Francisco, CA  94114-3707
                415-648-9279


                On Fri, Jul 25, 2014 at 3:55 AM, Turk6177 turk6177@... [johnmuirtrail] <johnmuirtrail@yahoogroups.com> wrote:
                 

                Great info. Thank you. What happened to the 2012 data?  Was it really -22 as the low for all those nights? That seems like quite an anomaly. 

                Sent from my Fantastic iPhone 5!

                On Jul 24, 2014, at 21:59, "dbindsch@... [johnmuirtrail]" <johnmuirtrail@yahoogroups.com> wrote:

                 

                I'm planning to hike the JMT beginning on Sept. 4th. So one of my concerns has been having the appropriate gear for September temps. Particularly because I've focused on lightweight backpacking the past couple of years. So I'm looking to keep my base wt down in the 10-12 lb range, which means careful choices about (especially) sleeping gear and clothing.

                So I've followed the lead of several of the long-time members here (particularly John Ladd) and done an analysis of temps from 8/24 - 10/7 for 2009-2013. The spreadsheet and plots are in the Files area under "Weather" so anyone can take a look and draw their own conclusions. The data are from the CDEC website (see the spreadsheet for details) and are from the Bishop Pass Station, which is one of the few at 10,000 ft or above (it's at 11,200)

                My conclusions are as follows:

                - Temps in Sept show a general downward trend of a few degrees per week. However, the variability at the low end seems to increase significantly in the latter half of the month (at least for the 5 previous years). In other words, its much more likely to experience a suddenly, significantly colder  night or two in the latter part of Sept.

                - For elevations at 11K or so, there is a reasonable likelihood of temps dipping into the 20's at night, but it's not common. Temps below 25 degrees only occur 10% of the time in Sept. Temps below 20 degrees only. Note that the dry adiabatic lapse rate is ~5.5 deg per 1000 feet, so camping at (say) 9000ft one would expect to be roughly 10 deg warmer than at 11K feet.

                - Since I'll be at the highest elevations nearer the end of the month, I should be prepared for temps down in the 20s, or expect to spend at least one to three nights shivering. I also got some great feedback from folks over on Backpackinglight's website, indicating that it's wise to be prepared for nasty weather to accompany a cold snap.

                For anyone interested, my gear list can be found at this link



              • nedtibbits
                Calley, Before Mountain Education’s annual trips along the JMT in Sept. and Oct., my wife and I used to do the trail deliberately after Labor Day to stay
                Message 7 of 19 , Jul 25, 2014
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                  Calley,
                   
                  Before Mountain Education’s annual trips along the JMT in Sept. and Oct., my wife and I used to do the trail deliberately after Labor Day to stay away from the crowds and bugs of summer. Yes, the days are a bit shorter, the sun a bit lower, and the temperatures a bit cooler, but the weather, then, is “refreshing” and we like it better than the heat, dust, bugs, and sweat of summer. Although I only have 50 years of wonderful Sierra explorations under my belt, I’ll advise this:
                   
                  - Prepare for cooler temps and don’t be surprised if your water bottles freeze one night (pad, bag, and clothing adjustments from summer),
                   
                  - Be aware that there may be ice on the trail in places making for hazardous steps,
                   
                  - Expect that any precipitation that may come your way could turn into snow. Now, statistically (and I’m not the researcher Mr. Ladd is), the chances of snow in September and October do go up from summer, but the sierra usually gets an “Indian Summer” during the time before Thanksgiving, so any snow you may get (and we’ve usually had a 4 to 10-inch accumulation on our trips during that time of year) will probably be followed by sunshine and warmer temps to melt everything off so you can have drier feet, less slippery trail, and know where the trail goes. If you get more snow than a foot or it falls faster than an inch/hour, pitch your tent and wait for the sun. Don’t risk getting cold and wet! Snowfall at this time of year will be powder snow and if it is deep enough, you’ll need snowshoes and the going will be much harder (another reason for staying put until you’re ready to plow through it). Although a big “dump” may be rare during September-October, it has been known to happen. Think about what you will do if 2 or 3 feet of snow falls on you and the trail (Can your tent handle it? Will you have enough food to ride it out until it melts? If the weather stays nasty for days and you can’t get out, do you have communications for help? If you don’t have snowshoes, are your shoes waterproof enough to wade through snow? Will you be bringing gaiters to keep the snow out of your boots? If you do have to wade through snow, realize that you will only be able to go about 1mph, if that, will consume tons of energy, and be very fatigued. So, consider a 3 or 4-season tent that will handle a snow-load and the ability to cook inside your tent when the weather is too nasty outside.
                   
                  (This is not meant to scare you, but to open your eyes to what can happen and has happened to us several times over the years. Be prepared for the worst and enjoy the best!)
                   
                  The Sierras during this time of year can be incredibly beautiful and a very rewarding time to be there! Just be wise. My wife and I prefer cold temps and snow to the heat of summer, so we prefer to be out there Fall, Winter, and Spring.
                   
                  Food for thought. Just don’t go assuming “everything will be just fine...don’t worry!” because mountain conditions change quickly and unpredictably. Some will say these words are ridiculous and “fear-mongering” because they’ve always had risk-free, ideal conditions on their trips. The decisions of what you carry and why are yours. So are the consequences. Fall is beautiful, but the chances do go up for cold, ice, and snow. Your trip may be perfect, but you never know ahead of time. I’d rather carry “come-what-may” gear and clothing and extra food so I will be a happy camper when it is storming outside! HYOH.
                   
                   
                  Ned Tibbits, Director
                  Mountain Education, Inc.
                  www.mountaineducation.org
                  ned@...


                  Mission:
                  "To minimize wilderness accidents, injury, and illness in order to maximize wilderness enjoyment, safety, and personal growth, all through experiential education and risk awareness training."
                   
                  Sent: Friday, July 25, 2014 3:33 AM
                  Subject: [John Muir Trail] Re: Sept. weather on the JMT
                   
                   

                  Thanks for this analysis - I'm also planning to be on the JMT in mid-September, so I'm wondering if you can briefly summarize what you mean by "nasty weather" accompanying a cold snap? Afternoon storms, or something else?

                  Thanks!
                  Calley

                • dbindsch@rocketmail.com
                  Thanks for the comments, all. Straw_marmot is correct - I should have used the environmental lapse rate of about 3.5 deg per 1000 feet. And John s comments are
                  Message 8 of 19 , Jul 25, 2014
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                    Thanks for the comments, all.

                    Straw_marmot is correct - I should have used the environmental lapse rate of about 3.5 deg per 1000 feet.

                    And John's comments are well taken. I didn't attempt to correlate the Bishop data with Volcanic Knob. However, examination shows internal consistency - except for the group of data points at -22F (those are clearly spurious, Turk).

                    Campsite choice is always an interesting problem. Camping in a low area (e.g. near a lake) can be more sheltered from wind, but may be colder. Up higher, winds can steal any temperature advantage. A sheltered spot partway up a ridge might be the ideal.

                    A couple comments on the issue of severe weather. This came up when I posted my gear list on BPL (backpackinglight.com), with a couple experienced hikers noting the same possibilities that Ned brings up. One in particular noted an incident with inexperience hikers near Whitney. In his words, the experienced folks knew to bug out even though it was snowing. The inexperienced group stayed, got wet, then later tried to get out. They were found on the mountain. So part of the thought process if it starts snowing hard should be "how far is it to get out, and what pass(es) do I need to cross vs. where would be a good place to wait it out.

                    Keeping dry (or at least keeping key components of your sleep system and clothing dry) is a major priority. Food is less of a priority than warmth and shelter - no one starves to death in a week (unless already undernourished).

                    Calley, my expectations are that in Sept one might get rain or hail from thunderstorms, which can be very violent (was in one last July) but don't last much longer than 1-2 hours (and are less frequent in Sept than in July and August). If a front carrying a major storm moves thru, one could get rain or snow that lasts hours. And I suppose in the extreme one might see multiple storms come thru, so rain/snow lasting multiple days. Don't know that there has been a Sept occurrence in the Sierra of this kind of weather in recent history.

                    Ned - I appreciate your comments. Do you see a difference between Sept and Oct in terms of occurrence of severe weather / snow? My understanding has been that snow in Sept is rare and tends to be very transitory (light dusting vs 4-12 inches). Not that I would want to be unprepared (I do carry a SPOT and have experience dealing with August snows in the Colorado Rockies).

                    thanks,

                    Duane
                  • Ray Rippel
                    I was two days ahead of you, Ravi, summiting on the 12th. I had rain, snow, and hail at Guitar Lake. The morning on the summit was sort of blah at first, but
                    Message 9 of 19 , Jul 25, 2014
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                      I was two days ahead of you, Ravi, summiting on the 12th. I had rain, snow, and hail at Guitar Lake. The morning on the summit was sort of "blah" at first, but then the sun came out and it was quite dramatic. Thus this photo on my Twitter site: https://twitter.com/JMTBook


                      On Fri, Jul 25, 2014 at 1:25 AM, ravi@... [johnmuirtrail] <johnmuirtrail@yahoogroups.com> wrote:
                       

                      I completed the JMT on September 14 

                    • bill cathey
                      It s true that starvation wouldn t be a major worry, compared to keeping warm and dry, but it s necessary to keep in mind that food is the source of the energy
                      Message 10 of 19 , Jul 25, 2014
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                        It's true that starvation wouldn't be a major worry, compared to keeping warm and dry, but it's necessary to keep in mind that food is the source of the energy that will help keep you warm.

                        bill

                        On Jul 25, 2014, at 11:59 AM, "dbindsch@... [johnmuirtrail]" <johnmuirtrail@yahoogroups.com> wrote:


                        Keeping dry (or at least keeping key components of your sleep system and clothing dry) is a major priority. Food is less of a priority than warmth and shelter - no one starves to death in a week (unless already undernourished).

                        Duane

                      • straw_marmot
                        Food is also the source of the energy that makes your brain function. Quality of decision making deteriorates dramatically when you re short of food.
                        Message 11 of 19 , Jul 25, 2014
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                          Food is also the source of the energy that makes your brain function.   Quality of decision making deteriorates dramatically when you're short of food.
                        • ravi_jmt2013
                          Ray, the 14th was almost the opposite - partially clear right before sunrise but then the clouds came in a few minutes after sunrise and views were obscured!
                          Message 12 of 19 , Jul 25, 2014
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                            Ray, the 14th was almost the opposite - partially clear right before sunrise but then the clouds came in a few minutes after sunrise and views were obscured!  I'm glad that I missed the snow and hail at Guitar Lake.
                          • brucelem12
                            Great Portrait / Panorama photo Ray! Bruce
                            Message 13 of 19 , Jul 25, 2014
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                              Great Portrait / Panorama photo Ray!

                              Bruce


                            • Ray Rippel
                              Except that I should have remembered to take my headlamp off! On Jul 25, 2014, at 12:14 PM, brucelem12 wrote: Great Portrait /
                              Message 14 of 19 , Jul 25, 2014
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                                Except that I should have remembered to take my headlamp off!

                                On Jul 25, 2014, at 12:14 PM, brucelem12 <no_reply@yahoogroups.com> wrote:

                                 

                                Great Portrait / Panorama photo Ray!

                                Bruce


                              • Joe MacLeish
                                Message 15 of 19 , Jul 26, 2014
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                                  > Sitting in Dow Villa lobby - just completed JMT. Heading for Onion Valley and Kearsarge Pass to Roads End to start first leg of SHR. Expect better results than last year.
                                • robert shattuck
                                  GO JOE!!!! Been waiting to hear from you and looking forward to seeing you at the trailhead in another 4-5 days . . . BOB
                                  Message 16 of 19 , Jul 26, 2014
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                                    GO JOE!!!!


                                    Been waiting to hear from you and looking forward to seeing you at the trailhead in another 4-5 days . . . 

                                    BOB 
                                    http://www.summitpost.org/plans/view_activity.php?post_id=6480




                                    To: johnmuirtrail@yahoogroups.com
                                    From: johnmuirtrail@yahoogroups.com
                                    Date: Sat, 26 Jul 2014 10:53:29 -0700
                                    Subject: [John Muir Trail] Completed JMT and .....

                                     
                                    > Sitting in Dow Villa lobby - just completed JMT. Heading for Onion Valley and Kearsarge Pass to Roads End to start first leg of SHR. Expect better results than last year.

                                  • Joe MacLeish
                                    On schedule. See you then. Sent from my iPhone
                                    Message 17 of 19 , Jul 26, 2014
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                                      On schedule.  See you then.

                                      Sent from my iPhone

                                      On Jul 26, 2014, at 11:34 AM, "robert shattuck bobolonius@... [johnmuirtrail]" <johnmuirtrail@yahoogroups.com> wrote:

                                       




                                      GO JOE!!!!


                                      Been waiting to hear from you and looking forward to seeing you at the trailhead in another 4-5 days . . . 

                                      BOB 
                                      http://www.summitpost.org/plans/view_activity.php?post_id=6480




                                      To: johnmuirtrail@yahoogroups.com
                                      From: johnmuirtrail@yahoogroups.com
                                      Date: Sat, 26 Jul 2014 10:53:29 -0700
                                      Subject: [John Muir Trail] Completed JMT and .....

                                       
                                      > Sitting in Dow Villa lobby - just completed JMT. Heading for Onion Valley and Kearsarge Pass to Roads End to start first leg of SHR. Expect better results than last year.

                                    • Joe MacLeish
                                      I am currently in three rivers near Sequoia. Please let me know if you are still good to go. If you can get close I might be able to swing out and do
                                      Message 18 of 19 , Jul 29, 2014
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                                        I am currently in three rivers near Sequoia.  Please let me know if you are still good to go.  If you can get close I might be able to swing out and do something.  We are moving up to Kings Canyon tomorrow.

                                        Sent from my iPhone

                                        On Jul 26, 2014, at 11:34 AM, "robert shattuck bobolonius@... [johnmuirtrail]" <johnmuirtrail@yahoogroups.com> wrote:

                                         




                                        GO JOE!!!!


                                        Been waiting to hear from you and looking forward to seeing you at the trailhead in another 4-5 days . . . 

                                        BOB 
                                        http://www.summitpost.org/plans/view_activity.php?post_id=6480




                                        To: johnmuirtrail@yahoogroups.com
                                        From: johnmuirtrail@yahoogroups.com
                                        Date: Sat, 26 Jul 2014 10:53:29 -0700
                                        Subject: [John Muir Trail] Completed JMT and .....

                                         
                                        > Sitting in Dow Villa lobby - just completed JMT. Heading for Onion Valley and Kearsarge Pass to Roads End to start first leg of SHR. Expect better results than last year.

                                      • robert shattuck
                                        as per my other e-mails, good to go. can t wait. Bob forkfestreview.wordpress.comsparklefart.blogspot.com
                                        Message 19 of 19 , Jul 29, 2014
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                                          as per my other e-mails, good to go. can't wait. 

                                          Bob


                                          forkfestreview.wordpress.com
                                          sparklefart.blogspot.com

                                          http://www.summitpost.org/plans/view_activity.php?post_id=6480




                                          To: johnmuirtrail@yahoogroups.com
                                          From: johnmuirtrail@yahoogroups.com
                                          Date: Tue, 29 Jul 2014 17:53:08 -0700
                                          Subject: Re: [John Muir Trail] Completed JMT and .....

                                           

                                          I am currently in three rivers near Sequoia.  Please let me know if you are still good to go.  If you can get close I might be able to swing out and do something.  We are moving up to Kings Canyon tomorrow.

                                          Sent from my iPhone

                                          On Jul 26, 2014, at 11:34 AM, "robert shattuck bobolonius@... [johnmuirtrail]" <johnmuirtrail@yahoogroups.com> wrote:

                                           




                                          GO JOE!!!!


                                          Been waiting to hear from you and looking forward to seeing you at the trailhead in another 4-5 days . . . 

                                          BOB 
                                          http://www.summitpost.org/plans/view_activity.php?post_id=6480




                                          To: johnmuirtrail@yahoogroups.com
                                          From: johnmuirtrail@yahoogroups.com
                                          Date: Sat, 26 Jul 2014 10:53:29 -0700
                                          Subject: [John Muir Trail] Completed JMT and .....

                                           
                                          > Sitting in Dow Villa lobby - just completed JMT. Heading for Onion Valley and Kearsarge Pass to Roads End to start first leg of SHR. Expect better results than last year.



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