Expedition Meteorology | Denali, May 2026

The project of Tobi, Heli and Laetitia to climb Denali, sounded always both exciting but also daring. The three had no strong résumé in high-altitude mountaineering and neither did I in regards of expedition meteorology. But certainly the four of us embarked well-prepared and -trained into uncharted and challenging terrain.

The importance of reliable weather forecasts was affirmed just some weeks before the start of the expedition. On a climbing trip I met a guy who’s grandfather, some long time back in the 1970s, lost his fingertips due to frostbite when taking off his gloves to fix the tent on Camp V in a 3-day snow storm at -40°C on the first repitition of the Cassin Route - so the legend goes.

My preparation was to review all available specialized weather resources and understand how others work the problem. But most importantly Tobi, Heli and Laetitia explained what they would wish for. I managed to fulfill most of their wishes by new versions of the PowderGram, feeding it with

• the global ICON forecast, with 13 km grid spacing, for an estimate of the mid-range (7.5 day) weather conditions, and with

• high-resolution forecasts for the mountains of Alaska, WRF-HRRR, run by NCEP, with 3 km grid spacing, for the most precise short-term (48h) forecast.

The obvious technical problem is the discrepancy in model orography against real orography. While Denali in reality rises to 6190 m.a.s.l., in WRF-HRRR it is at about 4000 m.a.s.l., while in ICON it is at only 2650 m.a.s.l.. For this reason model near-surface properties are challenging to interpret. Temperature is easiest to handle, it is simply extrapolated dry-adiabatically, which can only underestimate temperatures on the mountain. About humidity I would argue that one should also adjust for temperature, but eventually humidity is in high altitudes not important for as long as it does not mean cloudiness. And in regards of winds, I would argue that on mountains and ridges winds are much better represented than we would think, while winds in valleys are difficult to handle.

Summarizing the advantages of using PowderGrams

• I know what is done

• all information in one graph

• automatic computation and availability on map.powderguide.com

• precise localization

• confronting valley, mountain and circumference averages

• forecasts in text or PowderGrams as images can be sent via Garmin messenger.

Summit Push Situation

15/05: I see this day due to calm winds and despite limited visibility as favorable for getting back up to Camp V.

16/05: I must warn in regards of the winds, and the wind chill temperatures. Else, I see excellent visibility until late in the day, and obviously no precipitation. Only by midnight cloudiness is forecasted to return.

17/05: Winds remain at moderate speeds, gustiness increasing, maybe to beyond -75 km/h. Unmounting Camp V can pose a challenge. But eventually you can judge on 16/05 yourself, the windiness is similar, only gustier on 17/05. No significant precipitation forecasted. Mixed visbility, no whiteout to be expected, and even sunshine possible.

18/05: Weather situation not changing much. Gustiness calming down.

19-21/05: No storm to be expected, but precipitation possible. A retreat to Base Camp nevertheless should be possible. Note that I do not see a favorable and sunny weather window here.

21/05 seems sunny, but this is long time ahead.

Eventually the team decided to go fast, skipping Camp V, and to avoid the high winds forecasted. They left their tent in Camp IV at around 1AM. During their ascent I kept on updating them, using the WRF-HRRR-AK, which is refreshed 3-hourly, and assuring them in regards of the threat that were the winds arriving. Eventually in a 32-hours effort, Tobi and Heli made it from Camp IV to the summit and back. They proved both their skills as alpinists as well as the perseverance of high-altitude mountaineering. I am happy and satisfied about my forecasts being of vital help in their expedition.

Bolivian First Descents by Schulz et al.

Alongside the North-American adventures, a team around Malte Schulz opted for steep ski descents in the Bolivian Andes, in late April / early May 2026. Within not even 2 weeks they made quite likely the first ski / snowboard descents of

• Ancohuma, Bolivia (6427 m) — April 2026

• Parinacota, Bolivia (6380 m) — May 2026

• Chearoco, Bolivia (6127 m) — May 2026

Weather and snow conditions had been favorable and I am proud to say that my forecasts were certainly supportive.

Let us team up!

In case of interest in teaming up for an expedition, feel free to contact us via email.