Storm Forecast
Valid: Wed 25 Apr 2018 06:00 to Thu 26 Apr 2018 06:00 UTC
Issued: Wed 25 Apr 2018 05:52
Forecaster: PUCIK

A level 1 was issued Algeria mainly for heavy rainfall, large hail and severe wind gusts.

A level 1 was issued across Poland and W Belarus mainly for severe wind gusts and tornadoes

SYNOPSIS

A brisk zonal flow has established over much of W and Central Europe near and south of the frontal zone with windspeed easily exceeding 25 m/s at the 500 and 20 m/s at 700 hPa. A short-wave trough is evident in the satellite imagery, crossing Denmark as of 05 UTC Wednesday and translating fast to the E. A frontal system is associated with the trough and the cold front is forecast to cross Germany, Poland, the Czech Republic and much of Belarus by Thursday 06 UTC. To the S, a cut-off low resides over Algeria and over the extreme SE Mediterranean.

DISCUSSION

...Algeria...

A band of thunderstorms is already ongoing over the area at the moment in the environment of moderate CAPE and DLS in the range of 15 - 20 m/s, suggesting a potential for well organised DMC. Multicells and supercells may be capable of large hail and severe wind gusts, but forecast profiles suggest that heavy rainfall may pose the highest risk, given high RH in the low to mid-troposphere and flow oriented parallel to the initiating boundary.

... Poland to Belarus ...

Ahead of the fast moving short-wave and of the cold front, CAPE on the order of several hundred J/kg is forecast by NWP. Despite the fact that substantial cloud cover may hinder surface heating, it seems that models are well on track with the observed 2m dewpoint and temperature values, such that the simulated CAPE values are plausible. Isolated to scattered DMC will develop, perhaps including a few short line segments ahead of the cold front. Storms will form in strongly sheared environment, exceeding 20 m/s of 0-3 km and 10, or locally even 15 m/s of 0-1 km shear. Combined with LCL heights generally around 500 m, tornado threat will be present with any supercell. The threat may be diminished somehow by the presence of almost purely linear hodographs, while the threat of severe wind gusts may hindered somehow by the lack of well mixed boundary layer. Neverthless, combination of both suffices for Lvl 1.