Mesoscale Discussion
Valid: Wed 06 May 2015 12:00 to Wed 06 May 2015 17:00 UTC
Issued: Wed 06 May 2015 11:49
Forecaster: PUCIK

... Convective initiation expected within denoted areas with increasing threat of large hail and severe wind gusts ...

DISCUSSION

Surface observations show several convergence zones south and southeast of the Alps and Carpathians. Satellite loops and lightning detection reveal that thunderstorms are confined to the Alpine range at the moment. With continuing destabilisation during the afternoon hours, convective initiation is simulated along the convergence zones in the mountain forelands. The most probable zone of initiation, well in agreement by different NWP outputs will be SE Austria. Another well established convergence zone is observed over E Slovakia and Hungary.

Once convection initiates, storms should quickly organise with some becoming supercells as DLS exceeds 20 m/s. These will be capable of large hail and severe wind gusts. In case of isolated longer-lived supercells, 5 cm hail is not ruled out, even though CAPE values should stay mostly below 1000 J/kg. The highest chance for very large hail will be over N Italy, where initiation may be the most problematic.

Storms will spread E and SE-wards with time and may even affect areas outside the MD areas towards the evening hours.