Storm Forecast
Valid: Sun 20 Sep 2026 06:00 to Mon 21 Sep 2026 06:00 UTC
Issued: Sat 19 Sep 2026 11:53
Forecaster: TUSCHY

A level 1 was issued for the coastal areas of the S Baltic Sea to far NE Germany, N Poland and the W Baltic States mainly for a low-end severe gust and isolated tornado risk.

Numerous level 1 areas were issued for parts of the S-CNTRL Mediterranean mainly for heavy rain and isolated severe gusts.

SYNOPSIS and DISCUSSION

A rather quiescent pattern for DMC activity persists during this forecast period, as a dual jet configuration evolves over Europe.

A strengthening anticyclone builds up within this trap zone and affects most of W Europe, while a progressive trough crosses NE Europe with an active cold front passage.

A broad/flat upper trough covers most of the S-CNTRL Mediterranean with an augmented thunderstorm risk.

For the S-Mediterranean, another active day for slow moving thunderstorms is forecast with MUCAPE in the 1500 J/kg and DLS in the sub-5 m/s range. A moist airmass with TPWs in the 30-40 mm range (or up to 150% to the background climatology) support slow moving an regionally clustering convection with heavy rain the main risk. Isolated flash flooding is possible. In addition, a few short-lived wet-downburst events and isolated hail are possible despite only mediocre CAPE values.

Isolated NWP data points to a potential LL vortex spin-up E of Tunisia, which is not yet supported by most models/ensembles. However, if we get such a spin-up (both due to synoptic dynamics or driven by a bottom-down building positive PV anomaly within a long-lived thunderstorm cluster), locally heavy rain could become an issue for parts of E-Tunisia.

The level 1 from NE Germany to the Baltic States was issued due to a cold front passage and postfrontal convective activity. A 35kt 0-3km shear vector impignes with a small angle onto the cold front, so the setup is not ideal for an LEWP. Still a dried mid-level airmass overspreads the front and some low-end CAPE evolves mainly in the 0-3km layer. Despite CAA driven marginal SRH, an isolated tornado event is possible along those convetive breaks mainly from N Poland further NE, where LCLs lower. In addition, we added the coasts for a few severe (convectively induced) gusts, which is also valid for far NE Germany, where a somewhat deeper mixed BL persists.
We did not include Denmark for a gust-driven 1, as airmass dries out, while MUCAPE increases during the day, so confidence in gust-induced reports is too low for now. A spotty event cannot be ruled out however.