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2025 glacial outburst flood forecast is for “mid-August.” Currently this is not a concern for the race.

Two key actions will impact our course: 1. Suicide basin overtopping will result in closure of the HESCO barrier levee along Mendenhall River. 2. Mendenhall Lake level reaching 12 feet above USGS marker will result in Mendenhall (Back) Loop Rd bridge closure.

History & Planning

2024 threaded the needle. Rain and cold before, perfect on the day, glacial outburst flood a day later.

Jökulhlaups, cold water, record rains, and maybe even wild fires can impact our events. However, statistically, these shouldn’t be a problem. The first weekend in August was originally selected due to the historical temperature trends of Auke Lake and generally favorable weather. And being in a rain forest which has recovered from the 2016-2019 drought, we don’t anticipate wildfires this year.

Average temperature for the start of August is 57F/14C. Average high is 64F/18C. Average low is 49F/10C.

Severe weather or events could result in cancellation of the event. The following modifications are intended to mitigate or avoid certain types of risk.

Swim Modifications

These modifications follow the guidance found in the USAT Multisport Rules on pages 18-20. While not as exact, our thresholds for changes provide marks to help our organizers, safety partners, and racers with clear expectations. At the latest, a decision about modifications will be announced by 6:00am on race morning. Air temperature will be based on JNU airport reporting. Water temperature will use the ducky we have been reporting temperatures from since the start of July.

Swim Cancelled: Anticipate a short out and back run in place of the swim.

• Water temperature below 54F/13C
• Water temperature below 56F/14C & air temperature below 50F/10C

Swim Distances Modified: Sprint 500m, Olympic 1000m, Long 1200m.

• Water temperature between 54-56F/13-14C & air temperature above 50F/10C
• Water temperature between 56-58F/14-15C & air temperature below 50F/10C

No Modifications: Since this is the normal range temps for Juneau…

• Water temperature above 58F/15C & air temperature above 50F/10C

Bike modifications

In 2023 our event coincided with a jökulhlaup outburst flood of the Mendenhall River. If similar happens this year and the course cannot head towards the glacier, we will modify the bike course to be all “out the road.”

• Sprint Turn: Lynn Canal Fire Station
• Olympic Turn: Amalga Harbor Road
• Long Turn: just past the entrance to Echo Cove Road

If something like a wildfire, landslide, or unanticipated construction requires us to shorten the “out the road” section of the course for Olympic and Long distances, we will announce the new turn locations to create a lap within the existing course.

Run Modifications

It is statistically unlikely that anything changes our run course. The most likely event, but still incredibly unlikely, would be flooding of Montana Creek which would prevent us from using Black Bear Trail for the Olympic and Long courses. In that case, Olympic athletes will do two laps of the sprint course and Long distance athletes will do laps on a combination of out and back along Glacier Hwy and the Sprint course loop.