Storm Forecast
Valid: Thu 23 May 2019 06:00 to Fri 24 May 2019 06:00 UTC
Issued: Thu 23 May 2019 00:11
Forecaster: GATZEN

SYNOPSIS

Within a large area of relatively low geopotential, most of the forecast area is affected by weak mid-level flow, and deep layer vertical wind shear is only weak. Exceptions is a strong jet across south-east Europe ahead of the trough, as well as a small but intense cut-off low centred over southern Norway that is surrounded by strong mid-level winds. At the flank of this low, cool and dry air has spread into western Europe, whereas warmer and moister air is present across the eastern portions. Here, CAPE is forecast in response to diurnal heating.

DISCUSSION

Southern Russia, Belarus, Baltic States, eastern Poland, Ukraine, eastern Romania and Bulgaria, eastern Hungary, Balkans, Moldowa, northern Turkey

Within a moist air mass, diurnal heating is expected to lead to CAPE on Thursday. Except for the southern parts, CIN will be weak and initiation is likely. Given weak vertical wind shear, slow moving and weakly organized storms or clusters of storms are forecast. Main threat will be excessive precipitation with these storms given the slow movement. Highest potential is expected in the northern parts where skinny CAPE profiles with rich moisture are present.

An additional threat is large hail mostly expected in the eastern parts where CAPE is higher in the hail growth zone. Additionally, vertical wind shear gradually increases towards the east and south, supporting better storm organization such as multicells or supercells across southern Russia and from Bulgaria towards northern Turkey. Here, severe wind gusts are also not ruled out with the stronger storms.

Italy

Diurnally driven storms are expected. In weak shear, storms will be weakly organized. Locally, large hail and excessive precipitation are forecast.

Western France and northern Spain

Ahead of an approaching trough, frontogenesis is expected in the evening and night. A warm and slightly unstable air mass will be in place ahead of a cold front and thunderstorms are forecast. Given weak CAPE, potential of severe weather is limited. However, slightly increasing vertical wind shear may support some better organized storms, capable of severe wind gusts. Additionally, storms may cluster and pose a threat of excessive precipitation.