Storm Forecast
Valid: Wed 30 May 2007 06:00 to Thu 31 May 2007 06:00 UTC
Issued: Tue 29 May 2007 22:11
Forecaster: GATZEN

SYNOPSIS

Low geopotential has spread into western and central Europe. At lower levels, rather cool maritime air mass is present west of a cold front from Sweden to the eastern Poland and eastern Balkans. To the east of the cold front, warm and unstable air mass characterized by steep mid-level lapse rates/EML over north-western Russia as well as rich low-level moisture over most places.

DISCUSSION

North-western Russia

Very warm air mass has spread into western Russia ahead of the European trough. A well-developed EML was present in the range of this air mass as indicated by latest soundings. The northern surface warm front is expected near 60 degree north over north-western Russia. Ascends over this region indicate rich low-level moisture underneath the EML, yielding high CAPE in the order of 1000 J/kg. On WED, upper short-wave trough propagates northward at the eastern flank of European long-wave trough, providing QG forcing in the warm air mass over Russia. Initiation is most likely along the western part of the warm front over northern Baltic states, where low-level moisture flux convergence and QG forcing are expected to be strongest. Storms that form will likely become supercells due to low-level easterly winds and associated favorable veering as well as moderate deep layer vertical wind shear of 15 m/s. Large or very hail is expected to be the most significant threat. However, every supercells that forms will have a slight chance to produce severe wind gusts and tornadoes. Storms will likely spread eastwards along the warm front in the afternoon/evening hours. Further south, rather weak vertical wind shear is expected, and chance for organized convection is lower. However, given strong instability, a few large hail reports are not ruled out.

Belarus/western Ukraine

In the range of the cold front, low-level moisture convergence and diabatic heating is expected and thunderstorms are forecast. Given weak vertical wind shear, severe storms are not likely, but given strong instability, a few hail/wind reports are not ruled out with the stronger storms.