Storm Forecast
Valid: Thu 17 May 2007 06:00 to Fri 18 May 2007 06:00 UTC
Issued: Wed 16 May 2007 23:40
Forecaster: GATZEN

SYNOPSIS

European trough is only slowly propagating eastward and shows a tendency to cut off over Greece. At its eastern flank, upper southerly jet weakens during the period. At lower levels, frontal boundary stretches from western Russia to central Ukraine and further to Aegean Sea. To the east, warm air mass has become quite dry compared to Wednesday. Over north-eastern Atlantic, another long-wave trough starts to amplify.

DISCUSSION

Western Bulgaria, Romania, Ukraine, central Belarus, and western Russia

Along the frontal boundary, another round of convective activity is likely during the period. There are several indications that potential for severe storms has decreased again. Upper wind field is not that strong, while low-level cold air mass has spread far to the east. Additionally, warm air mass has become quite dry as indicated by latest soundings. As a consequence, outflow-dominant clusters of storms are expected to develop. Given quite impressive lapse rates in the warm air mass, severe wind gusts are expected to be the main threat. Best chances for severe convection exist over western Romania and Ukraine as well as central Belarus, where weak easterly winds will be present north of a surface low/frontal wave. Moderate forcing and vertical wind shear are expected to lead to some organized storms. As there are numerous boundaries in the warm air mass due to old convection, it is not ruled out that some cells may evolve into supercells, capable of producing large hail and severe wind gusts. Tornadoes are also possible in the range of old outflow-boundaries, where low-level buoyancy and wind shear may be favorable. Storms will likely merge into clusters that are outflow-dominant in the evening hours and are expected to decay during the night.