Storm Forecast
Valid: Tue 15 Apr 2008 06:00 to Wed 16 Apr 2008 06:00 UTC
Issued: Tue 15 Apr 2008 02:08
Forecaster: VAN DER VELDE

SYNOPSIS

A large upper trough stagnates over Europe, with lows/shortwave troughs passing over Romania/Ukraine, Italy/southern Balkan, and the UK. Between the large surface high pressure areas over western Europe and Russia an elongated zone of convergence exists where northwestern flow meets eastern flow. A warm unstable airmass is present in this zone, and thunderstorms will appear in the afternoon in an environment of a few hundred J/kg MLCAPE and cloud base heights of 1500-1800 m. Locally hail of 1-2 cm may occur, as well as flash-flooding due to slow movement of storms.

DISCUSSION

...Southern Balkan...

Positioning under the jet makes more dynamically evolved convection possible due to updraft interaction with vertical shear (20-30 m/s DLS). Some storms may develop rotating updrafts and pose a chance of isolated large hail, for which a marginal level 1 is issued. Low level shear and SREH are however not indicated (by GFS model) to be significant, and also CAPE is not very large (few hundred J/kg). Large-scale ascent from the trough coming out of Italy should aid activation of convective developments.