Storm Forecast
Valid: Mon 22 Sep 2025 06:00 to Tue 23 Sep 2025 06:00 UTC
Issued: Sun 21 Sep 2025 11:04
Forecaster: TUSCHY

A level 1 was issued for parts of the W/CNTRL Mediterranean for heavy rain, large hail, strong gusts and a few tornadoes.

SYNOPSIS

Over W Europe an extensive cut-off evolves during this forecast with residual energy lifting off towards Finland. In the meantime a blocking anticyclone resides over E-CNTRL Europe. This pattern assists in influx of a drier/more stable airmass into most of W/CNTRL Europe and Scandinavia with better quality moisture advecting NE/E towards Russia along the western fringe of the anticyclone. Deep moisture pools over the W Mediterranean, where the main DMC activity is forecast.

DISCUSSION

... Level 1 area ...

As the still digging cut-off over France approaches the level 1 area from the NW, a broad cyclonic SW-erly flow regime overspreads an unstable marine airmass.

MUCAPE resides in the 1000-2000 J/kg range with peaks near 3000 J/kg S of Sardegna. DLS improves from E to W with peak values near 15 m/s with strongest shear confined to the layer above 4-5 km AGL. Below, weak to moderate shear affects the unstable warm sector.

Not much synoptic-scale lift affects the area of interest although IPV maps show numerous low-amplitude waves, which exit the trough's base to the NE. These waves, combined with LL convergence along mesoscale (outflow) boundaries or along the orography/coasts should assist in constant CI during this forecast period - but more on a local to regional scale.
Dependant on where convection occurs, we could see an augmented flash flood risk f.ex. along the W-Italian coasts, where local training is possible (next to an isolated tornado risk). Some spots could see short time accumulations up to 100-200 l/qm with sharp rainfall gradients.

N Lombardy/Pidemont is another area, where localized training convection is possible with amounts in the 100-200 l/qm range for confined swaths.

Offshore activity could also be accompanied by large hail, strong gusts, heavy rain and a few tornadoes. The latter risk is especially enhanced in case of strongly deviating storm motions near convergence zones within the moist marine airmass.
Over N Algeria/Tunisia, large hail and strong to severe gusts become a concern with healthy convection. Clustering betimes adds also an heavy rain risk.

Overall the limited confidence in any hot spots and where f.ex. training coastal convection evolves preclude a level 2 upgrade for now.