High Risk Issued: Two-Day Severe Weather Outbreak Targets Balearic Islands, Italy and the Adriatic region

Severe weather outlook – forecast across Europe. This forecast highlights areas of organized severe weather, along with risk levels and severe weather threats across Europe. SEVERE WEATHER OUTLOOK   Valid: 09/09/2026 06 UTC – 11/09/2026 06 UTC Issued by: Severe Weather Europe Forecaster: Marko Korošec SUMMARY   *** A significant two-day severe weather outbreak is forecast across portions of western and northern Mediterranean from Wednesday through Friday afternoon this week. Moderate to extreme instability and strongly sheared environments combine for widespread thunderstorm activity with large to giant hail, severe winds, tornadoes, and damaging flash-flood potential from the Balearic Islands to southern France, northern Italy, and the Alps on Wednesday. Followed , Slovenia, Croatia, and across central Italy and the Central Adriatic region.***   A large, deep upper-level trough has emerged into western Europe and is moving east, with a strong blocking High to its east collapsing as it moves into Eastern Europe. Between these large-scale features, a strong southwesterly jet stream is providing ample wind shear, while the air mass beneath it is extremely humid, resulting from the historic marine heatwave over the Mediterranean. This outlook focuses on Wednesday’s and Thursday’s evolution, with a significant severe weather event forecast along the racing cold front from the Alpine region to the Balearic Islands on Thursday and across north-central Italy, Slovenia, Croatia, and the Adriatic on Friday. Robust and destructive thunderstorms are expected from Wednesday morning through Friday afternoon. Above: Video animation of the convective storm’s development across Central Europe and the Mediterranean from Wednesday through Friday night, September 9th and 10th, 2026. For this reason, HIGH + MDT risks have been placed across portions of the Western and Northern Mediterranean region, with highlighted areas where the most robust severe weather threat will develop on both days. The threat includes enhanced potential for severe damaging winds, destructive flash floods, tornadoes, and very large to giant hail (6-10 cm or larger).   SYNOPTIC OVERVIEW   This week’s weather pattern over Europe shows the underlying risk to the Balearic Islands, Italy, and the north-central Adriatic region on Wednesday and Thursday. As a deep wave over western Europe emerges further east and cuts off into the Northern Mediterranean, it creates a significant pressure and temperature gradient against the departing upper-level ridge to the east. This significantly amplifies southwesterly jet-stream winds from eastern Spain across the northern Mediterranean, providing violent wind shear. This brings a frontal system moving across Central Europe into the Mediterranean, with the cold front moving west to east from France and the Alps into Italy, Slovenia, and Croatia from Wednesday morning through Friday night.