Storm Forecast
Valid: Tue 04 Jul 2017 06:00 to Wed 05 Jul 2017 06:00 UTC
Issued: Mon 03 Jul 2017 19:46
Forecaster: DAFIS

A level 1 was issued for Poland and Belarus mainly for large hail and severe wind gusts.

A level 1 was issued for parts of the Alps mainly for large hail and severe wind gusts.

SYNOPSIS

West Europe will be under the influence of a ridge, while several short-wave troughs affect the other parts of the continent. The short-wave trough which caused damaging hail in Bulgaria, NE Greece and NW Turkey is moving fast east, over the Black Sea. Another short-wave trough travels from South Scandinavia towards the Poland and Baltic States, and it will be the main feature of todays forecast. Rather lower geopotentials over the Alps will create a more favorable environment for storms tomorrow. By the early morning of Wednesday, another short-wave trough will have approached the west coasts of the Iberian Peninsula.

DISCUSSION

.... Poland, Belarus and NW Ukraine ....

This area is expected to be under the left exit of a jet streak, where some significant advection of vorticity is forecast. At the surface, a cold front will move fast over Poland and Belarus, pushing a boundary of unstable air masses towards Ukraine. Under the development of 20-25 m/s DLS and meager MLCAPE, storms that will develop on this boundary will be able to produce large hail, but we expect no more than 2 cm, since NCAPE values seem rather low, as no steep lapse rates will be present. Moreover, strong downdrafts are expected within these storms, as 850 hPa wind speed will exceed 15 m/s. Storm activity will stop after 21z and maybe some remnants of elevated convection will still produce some flashes over Belarus and Russia.

.... Alps ....

Some slow-moving storms are expected over the Alps, where steep lapse rates and moist PBL will lead to the development of more than 1 kJ/kg CAPE in the afternoon. Forecast soundings show some fat profiles of CAPE mostly over the Italian Alps. A few storms may produce large hail and locally severe wind gusts. Storms will propagate slowly SE and will stop after sunset in most parts, but over N Italy elevated convection is expected during the night.