Storm Forecast
Valid: Tue 24 May 2011 06:00 to Wed 25 May 2011 06:00 UTC
Issued: Mon 23 May 2011 18:59
Forecaster: SCHLENCZEK

A level one threat was issued for NW Iberia mainly for large hail and to a lesser extent for severe wind gusts and excessive rainfall.

A level one threat was issued for SE-central Europe mainly for large hail and to a lesser extent for severe wind gusts.

A level one threat was issued for E-central Ukraine mainly for large hail and severe wind gusts and to a lesser extent for tornadoes and excessive rainfall.

SYNOPSIS

The upper trough of a low pressure system centered over the S Norwegian Sea will lead to some convective activity over the North Sea and the British Isles.

Most of the convection on Tuesday should be tied to a region with a marginal relative minimum in geopotential heights within a high pressure area which stretches from Tunisia NNE-wards to the E Black Sea. Overall shear and helicity is weak in this area but locally enhanced instability may allow a few severe weather events.

DISCUSSION

...NW Iberia...

Some hundred up to about 1000 J/kg MLCAPE are expected to be created mostly by diurnal heating over Portugal and N Spain. Isolated storms may develop within the airmass and may produce isolated large hail. Severe wind gusts due to evaporative cooling are not ruled out either and a marginal level 1 is issued. GFS shows locally intense QPF signals and an isolated flash flood event may be possible as well.

...SE-central Europe...

As seen also on the days before, there is a local maximum in instability located over Hungary and Slovenia / Croatia towards Bosnia and Serbia. Weak shear but quite steep mid level lapse rates and LCL / LFC heights about 1,5 km are forecast which will lead to a slight risk of severe wind gusts and isolated large hail.

...Ukraine...

A small upper cut-off low over W Russia moves eastwards and its cold front will affect the Ukraine and W Russia. The highest instability is likely to be located over the southern / central parts where the progression of the cold front is expected to be rather slow. Even though forcing is not really strong and deep layer shear is quite weak, some organised multicells may develop and could produce isolated large hail / severe wind gusts. An isolated brief tornado cannot be discounted either. Later in the period, storms will tend to cluster and heavy rainfall with local flooding is not ruled out.