Storm Forecast
Valid: Mon 02 Jun 2014 06:00 to Tue 03 Jun 2014 06:00 UTC
Issued: Sun 01 Jun 2014 18:02
Forecaster: PISTOTNIK

A level 1 was issued for Belarus and the Ukraine mainly for excessive precipitation and large hail.

SYNOPSIS

An extensive area of rather low pressure at all levels stretches from the British Isles across Central Europe and the Balkans to Turkey. It is flanked by a subtropical high to the Southwest and another blocking high over Russia.
Insolation gradually starts to heat the cool air masses over most of the European continent again. Dynamics are weak, and the last prominent surface cyclone is filling up while it regresses from the Western Ukraine into Northeastern Poland. The other noteworthy cyclones near Iceland and off the Libyan coast barely influence our forecast area.

DISCUSSION

... NE Europe ...

A tongue of warm and very moist air is advected northward in the warm sector of the occluding low. CAPE on the order of 1000 J/kg will build in response to diurnal heating. Highest instability will be centered over Belarus.
Isolated storms can already be active in the morning or initiate early, and by the afternoon and evening another round of widespread storms is forecast. With mostly weak vertical wind shear, single cells and pulse storms will be the dominant mode, followed by more or less rapid clustering. Excessive rainfall and large hail are the main risks. The former is maximized closer to the center of the low over Belarus where the storm coverage will be highest, and the latter is maximized over the Eastern Ukraine where deep-layer shear increases to 15-20 m/s near the diffuse trailing cold front.
Storms will go on into the night and will move northwestward while gradually becoming elevated and weakening.

... Aegean Sea, Turkey ...

An eastward moving vorticity maximum and a small body of particularly cold upper levels will likely fuel thunderstorm activity over the Northeast Aegean Sea before 12 UTC. Heavy rainfall and one or two waterspouts are possible.
Later in the day, thunderstorms will move onshore in Western Turkey or redevelop over the Turkish mainland. The subtropical jet starts to proceed northward, so the Southernmost storms might benefit from increasing deep-layer shear up to 20 m/s. However, magnitude of instability (a few hundred J/kg) and its overlap with the better shear regime are quite modest, so a better storm organization remains questionable. Extensive mid-level cloud coverage and limited insolation may be another limited issue.
In general, severe weather risk seems to be too low for a level 1 area both over the Aegean Sea and over Turkey.

... other thunderstorm areas ...

Limited and CAPE will regionally develop in response to diurnal heating and will soon be consumed into scattered thundery showers. Weak vertical wind shear makes severe weather unlikely.