Mesoscale Discussion
Valid: Sat 18 Jun 2016 12:00 to Sat 18 Jun 2016 15:00 UTC
Issued: Sat 18 Jun 2016 12:00
Forecaster: PISTOTNIK

... N Romania, Moldova, SW Ukraine ...

The first well-organized storm has formed over the North Carpathian mountains in the Botosani district in Romania, and satellite data show further towering cumulus clouds nearby. Latest surface observations confirm dewpoints between 16 and 20°C in this area, hence the CAPE magnitude suggested by forecast models (1000-2000 J/kg, locally more) seems realistic.

A decaying thunderstorm cluster has moved into the Ukraine to the immediate north of the highlighted area in the morning hours. Satellite data and surface observations (although they are sparse) suggest that it has sent an outflow boundary with northerly surface winds and slight cooling southward. Next to the convergence of upslope flow over the mountains, its leading edge will become another possible focus for convective initiation. Its most likely current position is from the southern border of the Botosani district across Moldova (near the town of Balti) into the southern Vinnytsia oblast in the Ukraine.

In their initiating stage, storms pose a primary risk of large hail, which could exceed 5 cm in size locally. Dangerous flash floods may occur as long as storms are backbuilding or anchored over mountains. A movement to the northeast and upscale growth could start towards the end of this MD's validity time.

... central Romania ...

Scattered storms are also about to initiate over the central Carpathians between Hunedoara and Brasov. Surface observations indicate somewhat lower dewpoints (13-17°C) in this area. Next to large hail, the higher cloud bases may promote severe downbursts. Due to the strong capping inversion, it is doubtful if storms can detach from the mountains and also affect the forelands later on.