Schweizer Sturmforum

Eastern France, south-western Germany, western Alps

Short update seems to be needed for the mentioned region. Low-level moisture has significantly increased and surface dewpoints around 20°C are present over parts of France, Germany, and western Alps. Given locally steep lapse rates as indicated by latest soundings over eastern France, at least weak instability can be expected. Latest satellite water vapor image also shows dark regions propagating from the west as upper jet streak moves eastward, and some DCVA is forecast. Latest satellite/radar images indicate initiation from south-western Germany to eastern France. Current thinking is that storms will go on during the night while spreading north-eastward into central Germany, reaching eastern Germany in the morning hours. Best potential for severe convection seems to exist where strong low-level shear will be present. Bow echoes capable of producing severe wind gusts as well as a few supercells capable of producing large hail, severe wind gusts and tornadoes are forecast during the next few hours over eastern France, western Alps, and south-western Germany. Limiting factor will be rather weak low-level lapse rates and associated limited low-level buoyancy, but given rich moisture and favorable low-level shear, even strong tornadoes may be possible. Thunderstorms will likely merge into mesoscale systems moving north-eastwards while severe threat will be mostly severe wind gusts and isolated large hail during the night hours.