Tag Archives: AC100

The Ups and Downs of the Angeles Crest 100 Mile Run

 

The white dome of Mt. Wilson Observatory from near the top of the Kenyon Devore Trail.
The white dome of Mt. Wilson Observatory from near the top of the Kenyon Devore Trail.

First published on June 30, 2015. Updated July 8, 2024.

August 3rd  runners from near and far gather in a small parking lot in Wrightwood, California, to start the Angeles Crest 100 Mile Endurance Run (AC100). Begun in 1986, the AC100 is one of the original five 100-mile U.S. endurance races. It has endured fires, floods, the Covid-19 pandemic, and changing trail restrictions.

There’s a tradition of running grueling endurance races in the San Gabriel Mountains. The Big Pines Trail Marathon was one of the first organized mountain ultramarathons in the U.S. First run in August 1934, its course used some of the same trails that AC100 runners enjoy today.

The AC100 is not like a road marathon. It is an entirely different kind of running event and an entirely different kind of running experience. The 2024 L.A. Marathon had about 25,000 participants. About 1/100th of that number — around 250 runners — are expected to start the AC100.

Sunrise from Blue Ridge during the 2015 Angeles Crest 100.
Sunrise from Blue Ridge during the 2015 AC100.

For many, one of the primary reasons for running the AC100 is to be fully immersed in the beauty and majesty of the San Gabriel Mountains. Runners start at 5:00 a.m., ascend the Acorn Trail, and as the sun rises, find themselves above 8000′, reveling in the spectacular views from Blue Ridge.

Even at this early stage of the race, the field is already becoming dispersed. By the time runners reach the first checkpoint, nine miles into the run, there is an hour spread between the first and last runner. Unlike a road marathon, much of the time a runner in the AC100 will be alone.

This year’s course returns to a point-to-point format, ending in Altadena. Because of damage to the Chantry Flat area by the Bobcat Fire, runners will bypass Chantry and ascend Mt. Wilson using the grueling Kenyon-Devore Trail, returning to the traditional course at the Mt. Wilson Toll Road above Idlehour.

As a result of this frequent storms the past two Winters, many trails have been damaged or blocked by trees and debris. Ultrarunners not only spend many hours enjoying the trails in our local mountains but also do hours of trailwork that helps keep trails open and usable for everyone.

This elevation profile for the 2024 AC100 course was created in SportTracks from a GPX file provided by the event organizers. The elevation profile was corrected using 3DEP 1-meter Lidar-based DEMs. A conservative elevation data smoothing setting was used, resulting in an estimated cumulative gain of about 17,890′ and loss of 22,550′. The actual gain and loss are probably a bit more. Placemark locations, mileages, and elevation gains and losses are approximate. The elevation profile can be downloaded from the Course Overview page on the AC100 website.

Estimated Angeles Crest 100 Mile Elevation Profile (link)
Click to download from AC100 Course Overview page.

In addition, here is an interactive, high resolution, 3D-terrain map of the 2024 Angeles Crest 100 Mile Race. It is based on the course GPX file downloaded from the AC100 website. The view is initially zoomed in on the climb up Mt. Baden-Powell. To change the view, use the control on the upper right side of the screen. Track and placename locations are approximate and subject to errors.

Click to view 2024 AC100 course with high resolution, photographic 3D terrain.
Click to view 2024 AC100 course with high resolution, photographic 3D terrain.

Here is another high resolution view of the Shortcut Saddle – Red Box – Mt. Wilson section of the AC100 course.

See the AC100 website for official information and details.

Crest and Clouds

Crest and clouds on the Pacific Crest Trail at 8900' near Mt. Burnham.

Crest and clouds on the Pacific Crest Trail at 8900′ near Mt. Burnham in the San Gabriel Mountains. From Saturday’s 30 mile training run on the PCT and AC100 course.

Cirrocumulus undulatus clouds above the San Gabriel Mountains. June 18, 2016.
Cirrocumulus undulatus clouds

Temps were a bit more manageable on Saturday than Sunday. Saturday the Big Pines RAWS (6964′) recorded a high of 79°F with an “in the sun” temperature of around 101°F. Sunday the Big Pines high was 89°F with a sizzling “in the sun” temperature of about 109°F.

In addition to the air temperature many Remote Automated Weather Stations (RAWS) report the fuel temperature. The air temperature is the temperature inside a ventilated, sun-shielded enclosure approximately 6 ft. off the ground. The fuel temperature is the temperature of a pine dowel in full sun near the ground. The fuel temperature is a good indicator of the much higher temperature runners and hikers can experience in exposed areas facing the sun.

Some related posts: Postcard Weather on the Pacific Crest Trail, What’s the Current Weather on the AC100 Course?

What’s the Current Weather on the AC100 Course?

Pacific Crest Trail on Kratka Ridge in the San Gabriel Mountains

A couple of weekends ago we had cool weather for a 28 mile Angeles Crest 100 training run from Islip Saddle to Chilao Flat. It was a bit windy and chilly at Islip Saddle, but once we were up and over the shoulder of Mt. Williamson the wind settled down and the weather for the remainder of the run was near perfect.

This was the second of four supported AC100 training runs, each covering a different section of the course. These organized runs account for just a tiny fraction of the total mileage a runner does to prepare for this event, and much of the mileage is done on the AC100 course.

Where is the AC100 course? Incorporating segments of iconic trails such as the Pacific Crest Trail, Silver Moccasin Trail and Gabrielino Trail, the AC100 starts in the mountain community of Wrightwood, California and ends in Altadena near JPL, traversing a large part of the San Gabriel Mountains.

Mountain weather — even Los Angeles County mountain weather — can be extremely varied and changeable. At about mile 18 the AC100 course reaches an elevation of more than 9,200′, near the summit of Mt. Baden-Powell. On the same day temperatures on the course can differ by 50 degrees or more. One section can be inundated by a flash flood while another is bone dry. During a Spring training run it might be 100 in the sun at Echo Mountain, while it is snowing on Baden-Powell.

Annotated Mt. Wilson Towercam Image
Annotated Mt. Wilson Towercam Image

The Mt. Wilson Towercam is usually pointed in the direction of the Angeles high country. When it is, it provides a great overview of about two-thirds of the AC100 course. The view extends from the top of the Acorn Trail at about mile 4 (in the distance on the far right), along the crest past Mt. Baden-Powell, Throop Peak, Twin Peaks and Waterman Mountain to Three Points at about mile 43. Chilao is hidden from view, but the Charlton Flat area and a section of Edison Road is visible on the left. Newcomb Saddle, at about mile 68, is on the lower right. Here’s an annotated Towercam image that shows the approximate location of these features.

Bill Westphal’s Altadena Weather & Webcam gives a lower elevation view of the San Gabriels, near the AC100 Finish. The view is NE toward the Sunset Ridge Trail and Mt. Lowe Road, around mile 93 or 94. The course goes from the right of the photo to the left, but is mostly hidden from view.

If you are willing to jump through some Java security hoops the Mountain Hardware Live Interactive Cam in Wrightwood is a couple blocks from the AC100 Start. It has views of downtown Wrightwood, Wright Mountain, the Heath Canyon landslide, Blue Ridge and several other locations. I temporarily enabled Java and followed the troubleshooting info linked on the web cam page. I’ve been able to get it to work on a desktop system using Firefox or Internet Explorer. Note that enabling Java and adding non-secure URLs to the Java exceptions list decreases the security of your computer.

Following are several Remote Automated Weather Stations (RAWS) and Weather Underground Personal Weather Stations (PWS) along or near the AC100 course, in order from Start to Finish.

It is important to note that the air temperature given by RAWS stations is the temperature inside a sun-shielded, ventilated enclosure 4-8 feet off the ground. Basically it’s the temperature in light shade. The temperature in full sun can be 15°F higher. I’ve found the “Fuel Temperature” to be a better gage of how hellish it’s going to be on exposed areas of trail. (The Fuel Temperature is the temperature of a ponderosa pine dowel in direct sun.)

Wrightwood KCAWRIGH7 PWS (5996′) – Approximately 0.25 mile W of Start. Was 55°F at 5 a.m. for 2015 AC100.

Wrightwood KCAWRIGH9 PWS (6000′) – Approximately 0.6 mile SE of Start. Was 59°F at 5 a.m. for 2015 AC100.

Big Pines BPNC1 RAWS (6964′) – Off Hwy 2 near Mountain High Ski Area. Top of Mt. Baden-Powell can be 12+ degrees cooler and much more windy. Was 64°F at 6:54 a.m. for 2015 AC100. Fuel temp at 11:54 a.m. was 92°F.

Mountain High Ski Area Base & Top Conditions – Approximate elevation of Base is 7000′ and top is 8000′. Compare Base temp to Big Pines temp.

Chilao CHOC1 RAWS (5450′) – Approximately 1.25 miles WNW of Chilao aid. Fuel temp at 1:53 pm was 95°F for 2015 AC100. Air temp at 6:53 pm was 79°F.

Clear Creek CEKC1 RAWS (3000′) – Approximately 6.8 miles W of Shortcut Aid (~4793′) and 2.9 miles W of Red Box Aid (~4620′). Was 71°F at 8:54 p.m. for 2015 AC100.

Mt. Wilson MWSC1 (5710′) – Approximately 1.5 miles NW of and 780′ above the top of Mt. Wilson Toll Road (~4930′). Compare to JPL 5600′. Was 69°F at midnight for 2015 AC100.

Henninger Flats HNGC1 RAWS (2800′) – Approximately 0.8 miles WSW of Idlehour Aid (~3168′). Marine layer can increase humidity on this section of the course. Was 69-70°F from 4 a.m. to 7 a.m. for 2015 AC100. Fuel temp was 89°F by 11a.m.

Altadena KCAALTAD18 PWS (1214′) – Approximately 0.6 miles S of Finish. For 2015 AC100 temp ranged from 66°F at 2 a.m. to 63°F at sunrise. Temp was 79°F at 9 a.m., 82°F at 11 a.m., and 86°F at 1 p.m. Humidity was high with dew point about 70°F.

Altadena KCAALTAD41 PWS (1348′) – Approximately 0.4 miles NW of Finish.

It’s not on the AC100 course, but the Mt. Baldy Ski Lifts Web Cams and Weather can be useful for estimating mountain temps and for Baldy area training runs.

Related post: The Ups and Downs of the Angeles Crest 100 Mile Run

Inspiration

Pine Mountain and Mt. Baldy from Lightning Ridge
Pine Mountain and Mt. Baldy from Lightning Ridge

The day before the Angeles Crest 100, after checking in for the race in Wrightwood, I drove over to Inspiration Point to have lunch, go for a short hike, and enjoy being in the mountains. The day was exceptional.

 

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