Mesoscale Discussion
Valid: Sun 29 May 2016 12:00 to Sun 29 May 2016 16:00 UTC
Issued: Sun 29 May 2016 12:40
Forecaster: PISTOTNIK

... S Germany ...

Satellite and radar data indicate that a band of mid-level clouds and a little rain/virga has crossed the Alps and is spreading over S Germany. This will finish daytime heating, and evaporating precipitation may even mix drier southerly mid-level winds down to the surface, limiting thunderstorm potential.
Plenty of insolation is still present ahead of this cloud band. The increasing thermal contrast makes immediate convective initiation likely near its leading edge, probably along an axis from the Swabian Jura via Munich to Salzburg.

... N Austria, Czech Republic ...

Renewed warm air advection overnight has created a capping inversion, and the boundary layer beneath it has been filled with widespread stratus/fog overnight. These cloud decks are reluctantly breaking up from the SE, but daytime heating is lagging behind the model forecasts.
Surface observations indicate dewpoints between 15 and 18°C, even up to 20°C in a narrow belt along the N Alpine rim with NE-erly upslope winds. The high CAPE values up to 2500 J/kg which were suggested by some NWP models could indeed materialize.

In both discussed areas, storms will move northward and will encounter substantial CAPE (e.g., 1400 J/kg according to the 12z Munich sounding) and E-erly to NE-erly surface winds which create regionally favorable veering to the S-erly wind aloft. An organization into multicells with a risk of large hail and flash floods can be expected, and one or several large clusters may evolve later on.
Uncertainties increase to the east, where CAPE is higher but latest observations still leave it open whether storm updrafts can form and persist against the capping inversion. Best chances for isolated "cap breakers" exist along the N Alpine rim and over the hilly terrain around the border triangle between Germany, Austria and the Czech Republic, but future data need to be awaited if they will give birth to a long-lived storm cluster which could affect Bohemia in the evening.