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⏵ Course guide · Utah ultra

Kat’cina Mosa 100K Mountain Run Course Guide

Kat’cina Mosa is the kind of 100K people whisper about. A single clockwise loop through the Wasatch above Provo, somewhere around 62 miles and 15,000-plus feet of climbing, most of it stacked into the front of the course, off a 3 AM start and a day that runs deep into the night. It gets called one of the hardest 100Ks in the country and that reputation is earned. I will walk you through the course first, where it is won and lost, then give you a pacing, crew, and fueling plan that respects the vert and the clock. Free calculators along the way to dial in your own numbers.

⏵ At a glance

Kat’cina Mosa 100K quick facts

Date
Typically a Saturday in early August (recently on hiatus, confirm the current year)
Location
Wasatch Range above Provo, Utah, starting near Springville
Distance
100K (about 62.2 mi), a single clockwise loop
Elevation gain
About 15,000 to 17,400 ft, with roughly 11,000 to 13,000 ft of it by mile 28.5 in three climbs
Start
3:00 AM (early start 1:00 AM for those who need the time)
Cutoff
Finish by midnight (about 21 hours), with intermittent aid-station cutoffs
Surface
About 48% dirt trail, 44% dirt road, 8% paved
Status
USATF Utah 100K trail championship and an ITRA-measured UTMB qualifier

These facts come from the official race site (Mountain Oasis Adventure Runs) and UltraSignup. The race has run on an early-August weekend and was recently on hiatus, so confirm the current year’s date, cutoffs, and aid stations in the race details before you commit. Logistics change year to year.

The course: where Kat’cina Mosa is won and lost

The loop runs clockwise and shares a good chunk of its early and mid miles with the Squaw Peak 50 trail. The thing to burn into your brain is that the course is front-loaded. Roughly 11,000 to 13,000 feet of the day’s climbing is done by mile 28.5, in three separate climbs, before you are even halfway. How you handle that first chunk decides your whole race.

The dark start and the first big climbs

You start at 3 AM in the dark, which sounds dramatic but actually works in your favor: the first climbs are cool and you are fresh. Resist the urge to hammer them. The early grade feels easy because you are rested and caffeinated and it is cold, and that is exactly the trap. Hike the steep pitches with purpose, keep your heart rate boringly low, and treat the first few hours as money in the bank, not a chance to bank time.

These opening miles climb toward the high country and the long pull to Lightning Ridge up around mile 19 or 20. It is a grind of a climb followed by a serious, steep descent off the ridge that drops thousands of feet in just a few miles. That descent is the first place the day starts billing your quads. Go down it controlled, light feet, short strides, because you have a long way to go.

The grind to Windy Pass and the backcountry middle

After the Lightning Ridge descent you turn and climb again, a long several-mile haul of a few thousand feet up to Windy Pass near mile 29 or 30. By the top of this one you have done the lion’s share of the day’s vertical and you are roughly halfway in distance. People who paced the first 28 miles with discipline crest Windy Pass tired but intact. People who raced the early climbs get here cooked, and the back half is no place to be cooked.

Around Windy Pass there is a real backcountry stretch with no crew access, you hike or run yourself through it, so this is a section to be self-sufficient on water and calories. Know it is coming, fill up before it, and do not count on bailing out or seeing your people in the middle of it.

The back half: less vert, more grit

The second half has “only” another few thousand feet of climb, which sounds like relief until you remember you already have 11,000-plus in your legs and the afternoon heat has arrived in the lower canyons. This is where the race becomes a mental event. The climbs are smaller but they feel enormous, and the long descents on tired quads are where badly paced runners fall to a painful shuffle. The intermittent cutoffs at places like Little Valley, Bath Tub, and Dry Fork are real, so keep doing the math on your buffer.

Then the sun goes down and you are likely back in the dark for the finish. A near-21-hour day off a 3 AM start means most of the field runs into the night on both ends. Pop your headlamp back on, settle in, and grind it out to the midnight cutoff. Finishing this thing is the achievement; chasing splits late is how people blow up.

Pacing strategy for a front-loaded, all-day 100K

With 15,000-plus feet of gain and most of it in the first 28 miles, Kat’cina Mosa is an effort-management race, not a pace-chart race. The whole game is getting through the front half with your legs and your stomach still working, then surviving the back half and the cutoffs.

Pace the climbs by grade, not by your watch

Your flat-ground pace is meaningless on these climbs. What matters is grade-adjusted effort: hold a steady, sustainable output and hike the steep stuff without ego. The single biggest mistake at Kat’cina Mosa is running the cool early climbs too hard because they feel easy, then unraveling after Windy Pass. Use a grade-adjusted pace to turn your real fitness into honest climbing and descending targets so you do not torch the first half.

Build a vert-aware finish prediction and work back to the cutoffs

Do not guess your Kat’cina Mosa time off a road race or even a flatter 100K. The 15,000-plus feet of climbing, the technical descents, the heat, and the night all add real hours. A vert-aware finish prediction that accounts for this course’s climbing gives you a realistic window, and from there you can work backward into the intermittent cutoffs so you know exactly how much buffer you should have at Big Springs, Little Valley, and beyond. On a 21-hour clock, knowing your margin at each checkpoint is the difference between a calm day and a panicked one.

⏵ Free tools to pace this course

  • Grade-adjusted pace calculator to turn your flat fitness into honest targets for the three big early climbs and the long descents.
  • Race-time calculator for a vert-aware finish prediction on this course’s climbing, so you can plan against the 21-hour clock and the intermittent cutoffs.
  • Race-equivalent calculator to turn a recent race result into a Kat’cina Mosa goal that actually accounts for the mountain.

Fueling, crew, and drop bags for a 100K that runs into the night

You could be out here anywhere from the low teens of hours to nearly 21, through cold pre-dawn, alpine exposure, and afternoon heat. Over a day that long, your stomach and your logistics matter as much as your legs. Get the fueling and the crew plan right and you give yourself a real shot.

Carbs: steady, trained, and relentless

For an effort this long, aim for something like 60 to 90 grams of carbohydrate per hour, and only push the top of that range if your gut is genuinely trained for it. The trap on a 100K is letting intake slide for a few aid stations because nothing sounds good, then bonking hours later with no way to dig out. Keep eating on a schedule, lean on things that go down easy when you are trashed, and practice your exact race-day carb rate on long back-to-back days so 70 to 80 grams an hour feels normal, not like a science experiment at mile 40.

Sodium, fluid, and the big temperature swing

You will start cold and finish in cooler dark, but the afternoon down in the canyons gets hot, and your sodium and fluid needs swing hard with it. Lean toward the higher end on sodium when it heats up, often around 500 to 700 milligrams per liter of fluid, and more if you are a heavy or salty sweater. Carry enough to get across the long gaps, especially the no-crew backcountry stretch near Windy Pass, instead of rationing to the next station and showing up empty. Weigh yourself before and after a hot long run to find your real sweat rate, then build the plan around your own number.

Crew, drop bags, pacers, and lights

Crew can meet you at a handful of road-accessible points, so plan those stops in advance: what you swap, what you grab, and how fast you get moving again. Pacers are allowed and a fresh set of legs and a clear head through the night miles is worth a lot when you are deep in the lows. Drop bags are not allowed at every aid station, so stage your night gear, extra food, and backup lights where you can actually reach them. Bring a primary headlamp for the start and a second light plus spare batteries for the finish, because you are running the dark on both ends.

⏵ Build your fueling plan

Get a carb, sodium, fluid, and caffeine plan per hour built for your weight, your goal time, and the Kat’cina Mosa heat and duration with the free ultra fueling calculator. Browse the rest of the free running tools at the tools hub.

⏵ Train for it with Summit Line

Get a race-day plan built around YOUR fitness, this exact Kat’cina Mosa course profile, and your projected splits. Summit Line reads your real training, builds a plan for 15,000-plus feet of climbing, and rehearses your fueling so race day is something you execute, not guess at.

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Kat’cina Mosa 100K FAQ

How hard is the Kat’cina Mosa 100K Mountain Run?

Very hard. It gets called one of the toughest 100Ks in the country for good reason. You cover about 62 miles with somewhere around 15,000 to 17,400 feet of climbing through the Wasatch above Provo, and the front of the course is loaded: roughly 11,000 to 13,000 of those feet come at you by mile 28.5 in three big climbs. Add a 3 AM start, high-alpine exposure, August heat down low, and a long day that runs into the night, and this is a race that asks for real mountain fitness and a plan, not just leg speed.

How much elevation gain does Kat’cina Mosa have?

The official numbers land around 15,000 to over 17,000 feet of total climbing across the 100K loop, with the same amount of descent since it returns to the start. The course is front-loaded: about 11,000 to 13,000 feet of that gain is done by mile 28.5 in three separate climbs, including the long pull to Lightning Ridge and the grind up to Windy Pass. The back half still has another few thousand feet, so do not expect it to be flat once the big early climbs are behind you.

What are the cutoff times for the Kat’cina Mosa 100K?

The race starts at 3:00 AM and the finish-line cutoff is midnight, so you get roughly 21 hours to cover the 100K. There are intermittent cutoffs at aid stations along the way (the early one at Big Springs around mid-morning is the one that catches people who went out too hard), so you cannot bank all your time for the end. An early start at 1:00 AM is offered if you need the extra cushion. Always confirm the current year’s exact cutoffs in the race details before you toe the line.

Why does Kat’cina Mosa start at 3 AM, and will I run in the dark?

Yes, you run in the dark on both ends. The 3 AM start (1 AM for early starters) exists to get the long, exposed high-country miles done while it is cool and to give the back of the pack enough daylight, but with a near-21-hour day most runners are also finishing in the dark. Plan on a headlamp for the opening climbs and bring a second light and spare batteries for the finish. Practice running technical trail by headlamp before race day so the dark does not wreck your footing or your pace.

How many aid stations are on the course, and can I have crew and pacers?

There are about 9 full aid stations plus a water stop and a spring, spaced roughly 3 to 8 miles apart, stocked with the usual ultra fare (fluids, fruit, candy, chips, potatoes, sandwiches, salt, and so on). Crew can reach you at a handful of road-accessible points, and pacers are allowed, which helps a lot through the long night miles. Note that drop bags are not allowed at every aid station, and there is a long backcountry stretch around Windy Pass with no crew access, so you carry yourself across that. Confirm the current crew points, drop-bag rules, and pacer policy in the official race details.

What is the weather and terrain like at Kat’cina Mosa?

It is a high mountain loop on dirt trail and dirt road (roughly 48% single-track, 44% dirt road, 8% paved) through the Wasatch, so you climb to real alpine elevation and drop back into the canyons. Early August can be cool and even cold up high in the pre-dawn dark, then genuinely hot down low by afternoon, so you dress and fuel for a big swing. Afternoon thunderstorms are a Wasatch summer regular, which matters on the exposed ridgelines. Treat heat and exposure as part of the race plan, not an afterthought.

This guide is independent and for planning only. The course details, dates, cutoffs, and aid stations come from public sources and can change year to year, and the race has been on hiatus, so confirm the current specifics with the official race before you register or run. The fueling and pacing advice is general and not medical advice.