Storm Forecast
Valid: Thu 11 Jun 2020 06:00 to Fri 12 Jun 2020 06:00 UTC
Issued: Wed 10 Jun 2020 22:25
Forecaster: GATZEN

A level 1 was issued across W Russia, Belarus, E Latvia, E Lithuania, E Poland for large to very large hail and extreme rainfall and to a lesser extent severe wind gusts.

A level 1 was issued across W and central Ukraine, Moldova and N Romania for large or very large hail, extreme rainfall, severe wind gusts and tornadoes.

A level 1 was issued for the Black Sea region mainly for large hail and extreme rainfall and to a lesser extend severe wind gusts.

A level 1 was issued across N Algeria mainly for severe wind gusts.

SYNOPSIS

Low geopotential extends across southern Europe. At its western flank, an intense cut-off diggs into the Bay of Biscay. Ridging is present across eastern Europe and Scandinavia. At lower levels, steep lapse rates have spread into the Black Sea region and farther north towards Belarus and advect west. These lapse rates overlap with rich boundary layer moisture that extends along a frontal boundary from W Russia to E Poland. Across W Europe, weak lapse rates and less moisture create a marginal set-up for thunderstorms.

DISCUSSION

W Russia to Belarus and E Poland

High CAPE is expected in the afternoon. Some frontal lift across Russia and numerous outflow boundaries farther south will be locations for new initiation. Vertical wind shear is weak, and most storms will be weakly organized. Stronger pulse storms will be capable of large or very large hail and severe wind gusts. Main threat is excessive rain due to the slow storm movement.

Romania, Moldova, Ukraine

Ahead of the low geopotential, enhanced flow from the east creates stronger vertical wind shear, and multicells are forecast to form. These will be capable of producing large or very large hail and excessive rain due to high CAPE. Severe wind gusts are also forecast, especially when clusters organize along their outflow boundaries. Additionally, tornadoes are not ruled out due to low-level curved hodographs and 0-1 km shear in combination with low LCLs.

Black Sea region

Along the Sea breeze convergence, convective storms are forecast in relatively high CAPE. While wind shear is weak to moderate, storms will be not too well-organized, however, local sea-breeze can increase the shear. Main threat is large hail and excessive rain, but severe wind gusts are not ruled out, especially in the eastern parts due to deeper boundary layer mixing.

N Algeria

Isolated storms across the Atlas can produce severe wind gusts in response to deep boundary-layer mixing. Deep layer shear is moderate and multicells are possible, however, weak CAPE will limit the potential of large hail.

NE Spain

In a strongly sheared environment, models predict some showers to develop. Convection initiation is questionable due to marginal CAPE and strong shear. If storms will develop, they can rapidly organize with a potential of large hail and severe wind gusts.