Extended Forecast
Valid: Wed 21 May 2025 06:00 to Thu 22 May 2025 06:00 UTC
Issued: Mon 19 May 2025 17:46
Forecaster: TUSCHY

A level 1 was issued for parts of the Balkan States mainly for isolated hail, severe wind gusts and heavy rain.

A level 1 was issued for the S Adriatic Sea mainly for an isolated tornado, heavy rain, hail and wind gust risk.

A level 1 was issued for parts of E Albania, N Greece into S N-Macedonia mainly for severe wind gusts and large hail.

SYNOPSIS

Once again a high-latitude blocking event (the last impact of the waning stratospheric final warming event of 9th March 2025) evolves with positive geopotential height anomalies stretching from the E Atlantic N towards Iceland. A broad cyclonic gyre over Scandinavia becomes established and supports the influx of a cool and rather stable airmass from the N.

Along the S fringe of that Scandinavian vortex, numerous low-amplitude waves shift SE/E: one over France, another one from Italy to the Balkan States and a third one deep into Russia.

Despite a broad plume of unstable air, covering most of S-CNTRL Europe, this airmass is either avoid of stronger shear or suffers from strong capping issues so the overall risk of organized DMC activity remains manageable.


DISCUSSION

... Adriatic Sea into the Balkan States ...

The passage of the weak and broad upper wave adds enough background forcing for scattered to widespread CI next to weak CIN and support from the complex orography (onshore).

The Dinaric Alps become one focus for more widespread CI during the day. As this activity shifts E it encounters a rather unstable (500-1000 J/kg MUCAPE) airmass with DLS around 10 m/s. A mix of pulsating convection and a few multicells poses a hail and strong to isolated severe wind gust risk next to heavy rain before thunderstorms start to weaken beyond sunset.

Shear increases towards the S Adriatic Sea (15 m/s DLS) and a few multicells and one or two transient supercells may pose an offshore and coastal heavy rain and large hail threat next to strong gusts. A rather warm/stable sub-900 hPa layer could hamper the tornado risk but an isolated event cannot be ruled out as not much modification for near surface based activity is needed.

Further SE, over E Albania into far N Greece and extreme S North Macedonia, a few elevated supercells are possible with large hail and severe gusts as capped 500-1000 J/kg MUCAPE overlap with 20 m/s DLS. However this area needs to be monitored closely for an eroding cap (like GFS is indicating) as otherwise 20 m/s 0-3 km shear and abundant 0-3 km SRH would point to an enhanced risk for swaths of severe wind gusts and large hail. This activity weakens until midnight as cap strength increases again after sunset.

... Lightning areas ...

The rest of the highlighted areas will see pulsating convection with local instances of heavy rain and or some hail and gusty winds. That far out no level 1 upgrade becomes necessary for any of those areas.