An updated version of the CLImate Wet snow sleeve ACcretion (CLIWAC) model is presented. The novelty lies in: refining wet snow thermal range and the criteria to distribute daily cumulative precipitation on an hourly scale; taking into account the sleeve accretion in dry snow conditions and partial shedding and melting; using wind data instead of parametrized wind values.

The comparison between the new estimates of Wet Snow Load (WSL) with the observations, acquired by the Wet snow Ice Laboratory Detection at Vinadio (Italy), showed better performance than previous results. In addition, the analysis of the new CLIWAC results, inferred from the MERIDA OI reanalysis, about the reconstruction of some Italian severe wet snow events in relation with the recorded failures in the energy supply, gave better results than before.

On the basis of daily data provided by 12 high-resolution (~12 km spatial resolution) Euro-CORDEX simulations, realized under the two emission pathways RCP8.5 and RCP4.5, CLIWAC was used to elaborate future projections of WSL on high voltage conductors (ACSR – d 31.5 mm) over Italy by 2100. To overcome the concept of “return time”, obsolete in a climate change context, the two frequency indices WSLD (Wet Snow Load Days) and WSLF (Wet Snow Load Frequency) were also estimated to elaborate future scenarios at short-, medium and long-term to investigate the probability of WSL exceeding some infrastructural thresholds from 1 kg/m to 18 kg/m. Weighted ensemble scenarios were computed, and the statistical significance of the projected variations was investigated through the Wilcoxon test and the agreement among the models.

The results highlight a general reduction in intensity and frequency of the extreme wet snow episodes, especially in RCP8.5, as rainfalls will prevail over snowfalls due to global warming, except for high Alpine altitudes, so far spared by this kind of events.