⏵ Course guide · Colorado winter 50K
The Human Potential Running Series closes its season with the Sawmill Trail Runs at Staunton State Park, a 50K, 16-Mile, or 8-Mile through Colorado high country in early December, with real winter conditions built into the plan. I will walk you through the terrain and the winter contingency rules first, then give you a pacing and fueling plan built for cold-weather racing. There are free calculators along the way to dial in your own numbers.
These facts come from the official Human Potential Running Series registration listing. Check the current year details before you commit. Race logistics change year to year, especially conditions for a winter event.
Staunton State Park ranges from high grassy meadows at 8,100 feet to granite cliffs over 10,000 feet, and Sawmill runs its 50K, 16-Mile, and 8-Mile through that full range in early December.
HPRS explicitly welcomes micro-spikes when conditions permit, and allows snowshoes if snow depth exceeds 6 inches. That is a direct signal from the organizers: plan for the possibility of snow and ice underfoot, and train or at least practice with traction devices before race day if you have never run in them.
If the 50K's first loop becomes unsafe due to deep snow, HPRS closes that loop and has 50K runners complete the 16-Mile course twice instead, back to back, to cover comparable mileage. Know this rule going in so a course change on race morning does not throw off your plan.
Sawmill started as a low-key "Fat Ass" gathering at White Ranch Open Space in 2013, became an official race in 2017, and moved to its current home at Staunton State Park in 2021. That history is part of why it is HPRS's season closer: a community race that has grown into a proper end-of-year test.
Winter footing changes pacing math more than most runners expect. The same grade that runs fast on dry August dirt can cost you significantly more effort under snow or ice.
A grade-adjusted pace target gives you an honest baseline for the climbing at 8,100 to 10,000-plus feet, but treat it as a starting point rather than a guarantee: snow, ice, or mud can all slow a section well beyond what elevation and grade alone would predict. The generous 11 to 12-hour windows exist for exactly this reason.
A vert-aware finish prediction, checked against your actual splits from the first few miles, tells you quickly whether winter conditions are costing you more time than planned, while you still have the whole race to adjust your effort accordingly.
⏵ Free tools to pace this course
Cold-weather racing changes fueling as much as it changes footing. Appetite drops in the cold, and gels can be harder to manage with cold hands and a cold gut.
Aim for roughly 45 to 75 grams of carbohydrate per hour, and lean toward warm, easy-to-manage food and drink where possible. Cold weather often makes typical race fuel less appealing right when you need it most, so know what you can actually stomach in the cold before race day, not on race day.
Sodium in the 300 to 500 mg per liter range is usually enough in cold conditions, since sweat losses run lower than on a hot day. Do not assume you need zero electrolyte replacement just because it is cold, effort and altitude still cost you sodium even when you are not visibly sweating.
⏵ Build your fueling plan
Get a carb, sodium, fluid, and caffeine plan per hour built for your weight, your goal time, and a cold December mountain day 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 Staunton State Park elevation profile, and your projected splits under real winter conditions. Summit Line reads your real training, builds a plan for cold-weather mountain racing, and rehearses your fueling so race day is something you execute, not guess at.
It is a legitimate winter mountain 50K. Staunton State Park spans grassy meadows at 8,100 feet up to granite cliffs over 10,000 feet, and a December date in Colorado means you should expect the real possibility of snow, ice, or cold on top of the elevation itself. HPRS explicitly plans for winter conditions, allowing micro-spikes and, in deep snow, snowshoes, which tells you this is not a race that assumes bare dirt trail.
HPRS has a published contingency: if the 50K's first loop becomes unsafe due to deep snow or treacherous conditions, that loop is closed and 50K runners instead complete the 16-Mile course twice, back to back, to cover a comparable distance. It is worth knowing this rule exists before race day so a course change does not catch you off guard.
Early December at 8,100 to 10,000-plus feet in Colorado means cold, potentially very cold, conditions, which changes fueling in ways summer racing does not. Aim for roughly 45 to 75 grams of carbohydrate per hour, and consider warm fluids and easy-to-eat food since cold weather can blunt appetite and make gels harder to manage. Sodium in the 300 to 500 mg per liter range is typically enough in cold weather, since sweat losses run lower than on a hot day. Layer your hydration and fueling plan around staying warm as much as around calories. Build your numbers with the free ultra fueling calculator before race day.
The 50K runs on a 7:00 AM to 7:00 PM window, a 12-hour allowance. The 16-Mile and 8-Mile both run 8:00 AM to 7:00 PM, an 11-hour allowance. Given winter conditions can genuinely slow a course down, these windows have real room built in for a snowy or icy day.
Staunton State Park's varied geology ranges from high grassy meadows at 8,100 feet to soaring granite cliffs over 10,000 feet, supporting a rich mix of terrain and wildlife. In December, expect that terrain under winter conditions: packed snow, ice, or mud depending on the year, which is exactly why HPRS permits traction devices and, in deep snow, snowshoes.
The event has built its own contingency plans for bad winter conditions, which is a good sign for a first-timer: the organizers are not pretending December in the Colorado high country is a non-issue. That said, cold-weather ultrarunning adds real logistics, layering, fueling in the cold, footing on ice or snow, on top of the usual demands of a 50K, so make sure you have trained and raced in cold conditions before treating this as your first ultra.
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<a href="https://runsummitline.com/guides/sawmill-trail-runs">The Sawmill Trail Runs course guide</a>This guide is independent and for planning only. The course details, dates, cutoffs, and winter-condition rules come from public sources and can change year to year, 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.