Extended Forecast
Valid: Mon 10 Jun 2019 06:00 to Tue 11 Jun 2019 06:00 UTC
Issued: Sat 08 Jun 2019 21:44
Forecaster: GROENEMEIJER

A level 2 was issued across parts of East Germany, Northwest Czechia and west Poland for large hail, severe wind gusts and heavy rain.

A level 1 was issued across parts of Germany, Poland, Czechia, Austria, Switzerland and Italy for large hail, severe wind gusts and heavy rain.

DISCUSSION

A broad southwesterly flow is located downstream of a deep trough over the British Isles. In the lower troposphere, a deep elevated mixed layer is advected northeastward from the Maghreb across Italy, reinforced by elevated heating across the Alps.

East and Southeast Germany, Poland, Czechia...

Low-level moisture will increase in a zone from south-central Germany to Northwest Poland as low-level winds converge as pressure falls. NWP suggest that between 1500 and 3500 J/kg to develop during the day, with the highest values predicted over Northwest Bohemia. Despite the fact that cirrus may be quite abundant, widespread convective initiation is forecast across and near the level 2 area. The environment is characterized by about 20 m/s of 0-6 km bulk shear, which suggests that some supercells will occur. Given that mid-level lapse rates are steep, a risk of very large hail (5+ cm) will exist. In addition, local severe wind gusts will be a prominent hazard. Later, storms will likely cluster, in particular over NE Germany and a mesoscale convective system may develop that tracks into Poland, producing wind gusts and heavy rainfall.

Northwest Italy...

Along the slopes of the Alps and the Alpine foreland, about 1000 J/kg of CAPE should develop during the day. NWP guidance suggests that convective initiation will occur relatively early in the day, within an environment featuring 25-30 m/s of 0-6 km bulk shear. A few well-organized supercells with a risk of large hail may develop that should gradually cluster while the main hazard shifts to local very heavy rainfall.