Schweizer Sturmforum

.... Switzerland, S Germany, and parts of Austria and the Czech Republic ....

Warm and moist air masses lie in the northern parts of the Alps where several lifting mechanisms are expected to trigger storms on Tue 29/06. First, synoptic lift during the advection of high mid/upper-level vorticity together with a surface cold front coming from the west will lift unstable air masses during the maximum diurnal heating. The presence of a mid-level jet increases DLS to 15-20 m/s which overlaps with high MUCAPE mostly in Switzerland, S Germany and the W Czech Republic. In addition, high PWAT values in NWP model outputs suggest that storms will be able to produce excessive precipitation, especially if an MCS develops. If isolated storms manage to develop, mainly ahead of the front, the main threat will be large hail and severe wind gusts, but also tornadoes are well possible. Curved forecast hodographs show veering wind profiles and locally enhanced SREH0-1km and low-level shear will be beneficial for tornadogenesis. The tornado, hail, and wind threats will be reduced during the night due to elevated convection, but flash floods will continue to pose a threat until the early morning on Wed 30/06.