Mesoscale Discussion
Valid: Tue 01 Aug 2017 17:00 to Tue 01 Aug 2017 20:00 UTC
Issued: Tue 01 Aug 2017 17:09
Forecaster: PISTOTNIK/GATZEN

A long wind shift line, interpretable either as a cold front or an outflow boundary, stretches from Lake Constance into SW Poland roughly along the NW-ern border of the highlighted area. Low-level cold air advection, cloudiness and a lack of diurnal heating have strongly reduced the thunderstorm risk anywhere northwest of this line.
Along the boundary, plentiful low-level moisture (2m dewpoints mostly between 16 and 20°C) and steep lapse rates aloft provide CAPE between 1000 and 2000 J/kg, confirmed by 12 UTC soundings. However, there is also a fairly strong cap in place. Best chances for convective initiation in the next few hours exist along the Ore mountains along the German/Czech border, where upslope flow from both sides helps to weaken the cap, and near the German/Polish border, where satellite imagery indicates (struggling) towering cumulus clouds.
If storms form, vertical wind shear is easily strong enough to support supercells with a risk of large hail and severe downbursts. The option of upscale growth into an MCS with a risk of more widespread severe wind gusts is limited by the strength of the cap, and it decreases hour by hour as convective initiation continues to fail.

The severe weather risk is immediately highest in S Germany, where a bowing line with embedded supercells from Switzerland is approaching. This storm system has already produced wind gusts up to 35 m/s and at least golfball-sized hail. It appears likely that it will survive into the Munich area, where 2m dewpoints are still between 17 and 20°C. There is an ongoing risk of severe to extreme wind gusts with the passage of this line, as well as large hail in case of an embedded supercell (especially at its southern end).
Storms will likely weaken after 20 UTC, when they encounter somewhat drier air further east (dewpoints 14-18°C) and nocturnal cooling of the boundary layer sets in.