Storm Forecast
Valid: Fri 27 Jun 2025 06:00 to Sat 28 Jun 2025 06:00 UTC
Issued: Thu 26 Jun 2025 23:46
Forecaster: PISTOTNIK

A level 2 is issued for E Romania mainly for severe convective wind gusts and to a lesser degree for large hail and excessive convective precipitation.

A level 1 is issued for Romania, Moldova, Bulgaria, North Macedonia, Serbia and Montenegro for severe convective wind gusts, large hail and excessive convective precipitation.

SYNOPSIS

An unseasonably strong, slightly meandering zonal flow still covers Europe with an axis between 50N and 55N. A short-wave trough and its attendant surface cyclone move from S Scandinavia towards Belarus and the Ukraine. Its diffuse cold front crosses the Balkans and Italy.
Another, stronger cyclone is centered near Iceland. Its warm sector overspreads the British Isles, and pronounced warm air advection starts building a mid-level ridge from Spain towards the North Sea. The mid-level flow slowly veers from W to NW over central and E Europe in response.
Temperature levels remain seasonable to above-average across most of Europe, with very hot and synoptically quiescent conditions still present towards the SE and SW.

DISCUSSION

... Balkans, Italy ...

The elevated mixed layer that has travelled across Spain, France and central Europe in the past few days overspreads the Balkans on Friday, though it weakens somewhat due to heavy convective overworking. Nonetheless, lapse rates are still steep enough to allow CAPE between 1000 and 2000 J/kg in a broad belt ahead of the advancing cold front, where low-level moisture accumulates beneath the capping inversion.
Unlike in the past two days, cold air advection creates a background of subsidence that is hard to overcome by the more confined lift of a short-wave trough embedded in the W-erly to NW-erly mid-level flow. Scattered thunderstorms will likely form in the afternoon and evening over orographic features and in general ahead of the short-wave trough. Deep-layer shear between 10 and 15 m/s (or somewhat less towards Italy) favors a multicellular storm mode, though the odd supercell is not ruled out. A few widely scattered large hail and excessive rain events or severe downbursts are expected, the latter further favored by the deep and well-mixed convective boundary layer, and are covered by a level 1. A confined area in E Romania is upgraded to a level 2, since convection-resolving models show one or two more concentrated swaths of severe wind gusts east of the Carpathian Mountains, where the best overlap between CAPE and vertical wind shear exists. Remaining convection will travel SE-ward towards the Black Sea while it turns elevated and weakens after sunset.

... central Europe to the Ukraine, south-central Sweden ...

Additional short-wave troughs overspread the cooler postfrontal airmass in these regions. Scattered, mostly daytime-driven and partly thundery showers are expected, but limited CAPE and weak to moderate vertical wind shear keep the severe weather hazards on the low side.