Storm Forecast
Valid: Tue 12 Jun 2018 06:00 to Wed 13 Jun 2018 06:00 UTC
Issued: Mon 11 Jun 2018 22:59
Forecaster: DAFIS

A level 2 was issued for Hungary, SE Austria, NE Croatia, NE Slovenia, N Serbia, W Romania and W Ukraine for large hail, severe wind gusts, excessive precipitation, and tornadoes.

A level 1 was issued for France, Switzerland, Austria, S Germany and N Italy mainly for excessive precipitation and severe wind gusts.

A level 1 was issued for N Balkans mainly for excessive precipitation, large hail, and severe wind gusts.

A level 1 was issued for parts of Romania, Ukraine, and Russia mainly for excessive precipitation and tornadoes.

SYNOPSIS

A long-wave trough in West Europe with several vorticity maxima has a twofold contribution to convective activity: first, it brings cold air masses in the mid-levels over unstable air masses in W Europe and second, it leads a plume of very moist air masses from the Mediterranean Sea towards C-E Europe. The steepest lapse rates are expected between Italy and N Balkans, in combination with up to 15 g/kg low-level mixing ratios, so MLCAPE is forecast to reach and exceed 2 kJ/kg.
A few more short-wave troughs will affect Scandinavia, SW Russia and Middle-East where several storms will form but the probability of severe weather events is low given the weak DLS and only marginally high CAPE (low NCAPE).

DISCUSSION

.... Level 2 area ....

During Tuesday 12/06 WAA from C Mediterranean towards C Europe and the Balkans will create a weak cap during the morning, but later in the afternoon, we expect several storms to form, fed by warm and moist low-level (LL) air masses. The DLS will be generally weak, only marginally exceeding 10-15 m/s in SE Austria and W Hungary, but 0-3km shear seems comparably strong, overlapping with 1.5-2 kJ/kg according to several NWP model outputs. Several storms will be able to become supercells and create all kinds of severe weather, mainly large hail and severe wind gusts. Moderate to strong LL shear with veering winds in E Hungary, S Poland, NW Romania and W Ukraine increase the probability of rotating updrafts able to produce tornadoes. More to the west and south tornadic activity will be limited but severe wind gusts will be an important threat due to high delta-Theta-e values in the model guidance.

.... France, Switzerland, Austria, S Germany, and N Italy ....

A cold-bubble over France creates steep lapse-rates along with the weak mid-level wind field. High PWAT suggests that stationary storms will be able to produce flash floods, especially in Switzerland and S Germany.

.... Balkans and Russia ....

Marginally high CAPE values are forecast in the Balkans and Ukraine - SW Russia. In the Balkans steep lapse rates and high PWAT increase the probability of large hail and excessive precipitation. High-resolution models forecast isolated storms that may become supercells, able to produce hail up to 3-4 cm.