Valid: Sat 05 May 2018 06:00 to Sun 06 May 2018 06:00 UTC
Issued: Fri 04 May 2018 23:08
A level 2 was issued for parts of Croatia, Bosnia and Herzegovina, and Serbia mainly for large hail, severe wind gusts and heavy precipitation.
A level 1 was issued for a corridor extending from W Russia through Balkan Peninsula up to Turkey mainly for the large hail, severe wind gusts and excessive precipitation.
SYNOPSIS and DISCUSSION
Almost stationary broad low overspreads W and CNTRL parts of Mediterranean. High overbuilds in the corridor from S British Isles up to S Scandinavia. A weakly amplified long-wave with a jet streak travels through N Atlantic with a secondary wave over Finland, NW Russia and Baltic Countries. SE Europe is under weakly diversified pressure field with a warm and unstable airmass, mostly dominated by steep lapse rates and enhanced boundary layer's moisture. Moderate instability under weakly sheared environment is expected to dominate over this area. Within the support of a strong diurnal heating, mostly isolated to multicell thunderstorms are expected to develop in the afternoon hours. Large hail up to 3-4 cm (given steep lapse rates), local downburst events (given enhanced delta theta-e) and excessive precipitation (given PW 25-30mm and slow storm motion) are the main threats within these storms. Excessive precipitation is predisposed along W Balkan Peninsula's mountain ranges where orographic lift and complex orography may results in a local flash flooding event. Highest chances for better organized storms involving multicell clusters and supercells are over parts of Croatia, Bosnia and Herzegovina and Serbia where a moderate ML CAPE (1000-2000 J/kg) will be supported by 15 m/s DLS and 150-250 m2/s2 SRH. Thunderstorms are expected to develop within the convergence zone in the afternoon hours. MCS in the late afternoon is possible. A local event of very large hail also cannot be ruled out, especially given proper convective mode (isolated supercell), environmental steep lapse rates and high ELs. Although convective activity will significantly drop in the late evening hours, in many places a local cells with weak lightning activity may remain during nighttime.