Schweizer Sturmforum

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Another risk is a flash flood risk as background flow is very weak. Areas, where thunderstorm coverage will be enhanced ( e.g. S / SW Germany, Belgium and the Netherlands and S/SE Switzerland ) could see an upscale growth of thunderstorm activity into a few loosely organized thunderstorm clusters. Please keep in mind that this risk is not implemented in our risk scheme.


... S - Germany , Belgium and the Netherlands ...

We decided to spend a few more lines for those areas as there could exist a hail threat, equaling a level - 1. Latest synop reports and modified soundings reveal potential modest instability release in an overall weakly sheared environment but wind field and hence DLS strengthened somewhat in the mid-levels compared to yesterday with some veering present. A PVA maximum crosses those areas during the evening / night hours from the SW and should cause enhanced thunderstorm development. At the moment we decided against issuing a level - 1 as shear and instability are too weak but a level - 1 may be issued later on mainly due to an isolated large hail risk.