Storm Forecast
Valid: Tue 17 Apr 2012 06:00 to Wed 18 Apr 2012 06:00 UTC
Issued: Mon 16 Apr 2012 23:02
Forecaster: KOROSEC

A level 1 was issued for parts of southern Balkans mainly for severe winds, large hail, tornadoes and excessive convective rainfalls.

A level 1 was issued for southern UK and NW France mainly for severe wind gusts.

SYNOPSIS

A complex setup across parts of Europe on Tuesday. A broad upper trough over south-central Europe rapidly advances east while becoming negative tilted by Wednesday morning. On its front flank, a secondary SFC low forms around Greece and rapidly intensifies while moving NE-wards. A frontal system affects the area with all kind of severe weather possible. On the back side of the trough, very cold mid levels overspread UK, while a deep SFC low rapidly moves towards SE.

DISCUSSION

... southern Balkans and SE Mediterranean ...

An aforementioned trough transformation results in a new cyclogenesis over S Mediterranean and deepening while moving onto Greece by Wednesday. A surface low over S Adriatic sea slowly diminished meanwhile. A large scale ascent will be available for widespread convective activity as well as strong WAA from the south. This will result in unstable airmass across the warm sector. Once the strong cold front accelerates from Ionian sea eastwards, storms will reorganize and gain intensification within the moderately sheared environment. Expect severe storms as well with threat for large hail, severe winds and a lot of intense rain locally. With enhanced SREH/shear in the lowest levels, LL mesocyclones will be possible, posing a threat for a few tornadoes as well. Storms should cluster into a large system overnight while advancing into Aegean sea. Therefore additional threat for intense rain and severe wind gusts will exist. However, threat seem to warrant a high-end level 1 while activity will be closely monitored for an upgrade into level 2 if needed.

Another surface frontal zone extends from western Russia SW-wards across central Ukraine and Bulgaria where some destabilization is expected along it mostly during the daytime hours when some instability will release. But rather marginal shear seem to limit organized severe storms, however some intense cells could be possible with threat mainly for severe winds and large hail. But too sporadic to warrant a threat level.

... southern UK towards NW France ...

A deep surface low rapidly translates from Ireland SE-wards across the UK, characterized by intense wind field. Marginal instability will result from steep lapse rates behind the cold front which should support widespread showers and thunderstorms in cold maritime airmass, some of them could bring some marginal hail. While early in the forecast period, some convective activity cannot be excluded along the leading edge of the cold front, placed within the highly sheared envirnment. However, a marginal level 1 has been issued to cover mostly the severe winds threat.