Snow outlook
How much longer will Transjurassienne have snow?
Historical snow depth averaged over a ±15-day window around each race date, combined with CMIP6 climate projections to 2050. Adjust the minimum threshold below to see how the danger profile changes.
Historical trend
-5.1cm
per decade (linear regression)
Last observed
18.4cm
±15d mean in 2026
Years with data
77
snow records
±15-day mean around race day · OLS regression · CMIP6 (MPI-ESM1-2-XR) median projection
Risk threshold
Minimum snow depth considered race-viable
58%
High risk
14 of 24 projected years are expected to have less than 5 cm on race day (CMIP6 median). First at-risk: 2028 · Last: 2050.
Projected at-risk years — CMIP6 median < 5 cm
| Year | Mean (±15d) | Trend | Readings |
|---|---|---|---|
| 2028 | 1.2 cm | 21.2 cm | 31 |
| 2032 | 1.9 cm | 19.1 cm | 31 |
| 2035 | 4.6 cm | 17.6 cm | 31 |
| 2036 | 2.4 cm | 17.1 cm | 31 |
| 2037 | 1.3 cm | 16.6 cm | 31 |
| 2038 | 2.7 cm | 16.1 cm | 31 |
| 2039 | 3.3 cm | 15.6 cm | 31 |
| 2040 | 3.1 cm | 15 cm | 31 |
| 2041 | 3.6 cm | 14.5 cm | 31 |
| 2043 | 0.4 cm | 13.5 cm | 31 |
| 2044 | 2.5 cm | 13 cm | 31 |
| 2048 | 0 cm | 10.9 cm | 31 |
| 2049 | 2.3 cm | 10.4 cm | 31 |
| 2050 | 4.9 cm | 9.9 cm | 31 |
How projections are built
01
ERA5-Land archive
Open-Meteo serves snow depth from ERA5-Land (ECMWF reanalysis, ~11 km, 1950–present). For each year, the mean is computed over the ±15-day window around the reference race date. ERA5-Land tends to overestimate snow depth at coarse resolution.
→02
CMIP6 scenarios
Multiple runs of MPI-ESM1-2-XR under SSP2-4.5 and SSP5-8.5 pathways provide daily Tmin, Tmaxand precipitation projections from 2025 through 2100.
→03
DDF snowpack model
A Degree-Day Factor model runs day-by-day on each CMIP6 run. Precipitation falls as snow when Tmean < t_seuil, and melts proportionally to degree-days above it. Snowpack age increases resistance to both melt and fresh accumulation. Parameters are calibrated against ERA5-Land.
→04
Risk score
For each projected year, the DDF output is averaged over the ±15-day window. The danger score counts the share of future years whose mean falls below your chosen threshold.
DDF model — calibrated parameters
t_seuil1.0 °CTemperature threshold — precipitation falls as snow below, triggers melt aboveddf3.2 cm·°C⁻¹·d⁻¹Degree-Day Factor — cm of snowmelt per degree-day above t_seuilswe_depth_factor0.30 cm/mmFresh snow density — 1 mm of solid precipitation ≈ 0.30 cm snow depthrain_effect0.20Fraction of liquid precipitation that accelerates snowpack meltaging_rate0.05 d⁻¹Hardening constant — resistance = 1 − e^(−0.05 × age_days)melt_resistance_weight0.60Old, dense snowpack resists thermal melt by up to 60 %accum_resistance_weight0.50Old snowpack compresses under fresh accumulation (up to 50 %)rain_resistance_weight0.30Old snowpack resists rain-induced melt by up to 30 %Parameters calibrated by minimizing RMSE against ERA5-Land observed snow depth. Calibration range: t_seuil ∈ [−1, 1] °C · ddf ∈ [2, 4] · swe_depth_factor ∈ [0.05, 1.0].