Extension of the vigilance orange in the departments of Isère and Ain.
Rain started in the Cévennes foothills last night, but no precipitation elsewhere this Thursday morning.
The extension of the axis of heavy rains going from the south of Ardèche to Bugey is still relatively uncertain, particularly in terms of expected accumulations in the north of Isère and the east of Ain. However, these expected rains are occurring in a short time, and in areas already impacted last Monday, which implies the extension of orange vigilance to two departments.
Rain Flood: Intense rain-storm episode requiring special monitoring due to its intensity and duration.
From the beginning of the afternoon, a first succession of storms could generate very intense precipitation on an axis going from the south of Ardèche to the north of Drôme, possibly spilling over into the north of Isère
Subsequently, a rain-storm front crosses Rhône-Alpes, not very mobile in nature as it approaches the Alps, again causing precipitation from the south of Drôme and Ardèche to Bugey, via the north of Isère, impacting to a lesser extent a priori the west of Savoies.
If these storms can locally generate hail or gusts of wind of around 70 to 80 km/h, it is especially the intense precipitation, both instantly and in accumulations over a few hours, which should cause the most significant damage. .
Thus, accumulations of 60 to 80 mm are possible, or even locally 100-130mm in a pessimistic scenario, with intensities of 40 to 60mm/h, and this on an axis that could affect the areas already impacted last Monday (for comparison the extraordinary accumulations last Monday reached 130 to 200mm in the space of 12 hours, and even 275mm recorded in the north of Ardèche).
2023-09-21 09:28:55
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