Storm Forecast
Valid: Fri 24 Jun 2011 06:00 to Sat 25 Jun 2011 06:00 UTC
Issued: Thu 23 Jun 2011 19:20
Forecaster: TUSCHY

A level 1 was issued for areas from Croatia to Ukraine mainly for large hail, severe wind gusts and excessive rainfall.

A level 1 was issued for NE-Poland to Estonia mainly for isolated large hail.

SYNOPSIS

Large-scale trough moves slowly to the east and affects most parts of N-Europe. Quiescent conditions are forecast over the Mediterranean with broad ridge in place.

DISCUSSION

... Croatia to Ukraine ...

Surface cold front surges southeastwards. Prefrontal air mass is moist, unstable with MLCAPE of 1000 J/kg and weakly capped. Also, rough topography assists in support for initiation and scattered thunderstorms are forecast. A modest (20 m/s) 500 hPa jet overspreads the baroclinic zone with gradual weakening during the forecast period. Enough speed and directional shear forecast for organized multicells/a few supercells with large hail and strong to isolated severe wind gusts. Convection becomes more disorganized after sunset with weakening shear and CAPE. Messy storm mode is expected with mainly an heavy rainfall risk.

...S-Norway, parts of Germany and Poland ...

Cold upper low and advection of a maritime air mass creates a favorable environment for daytime driven convection....probably a few vigorous updrafts included. Shear will be weak, so the dominant storm mode will be a pulsating one. Nevertheless, marginal hail, an isolated large event possible, and strong wind gusts accompany stronger activity. Thunderstorms weaken after sunset.

Storms may find a marginal better sheared environment over NE Poland to Estonia with DLS of 15-20 m/s and marginal CAPE. A large hail risk was the reason for upgrading that part.