Storm Forecast
Valid: Fri 20 Jun 2025 06:00 to Sat 21 Jun 2025 06:00 UTC
Issued: Thu 19 Jun 2025 14:01
Forecaster: TUSCHY

A level 1 was issued for parts of Sicily and surroundings mainly for locally very heavy rain, some hail, strong gusts and a low end tornado risk.

A level 1 was issued for parts of far NW Italy and surroundings mainly for locally heavy rain, hail (an isolated large event not ruled out) and strong to severe downburst events.

SYNOPSIS

A more or less tranquil pattern continues over Europe with a blocking ridge persisting over SW/W into CNTRL Europe. In the meantime, numerous progressive troughs cross W Russia and far E Europe to the S/SE.
A long-lived cut-off over Sicily weakens while drifting E with otherwise no noteworthy feature to mention regarding DMC probabilities.

DISCUSSION

... Sicily to Calabria ...

The cut-off delivers another active day with thunderstorms for the mentioned area. Despite the partially worked-over mid-tropospheric airmass due to convection from the previous days with lowered mid-level lapse rates, rich BL moisture offshore and along the coasts still supports MUCAPE in the 1000-2000 J/kg range. Sub 10 m/s DLS improves a bit towards N Sicily (also with 0-3 km shear aoa 10 m/s), but this belt of stronger shear should stay to the N of most convection.

Expect another round of repeated CI with slow moving thunderstorms. Heavy rain on the local scale, some hail and strong downburst gusts are forecast. In case a storm taps into the very moist coastal airmass, an isolated tornado is not ruled out but mesoscale dictates that risk. A few waterspout events beneath the upper low are still possible. This activity weakens after sunset.

A level 1 was added mainly for the local flash flood risk with very effective to isolated extreme rainfall rates along the orography, which is fostered by lingering mid/upper level (modified tropical) moisture near the upper vortex' center.

... NW to far N Italy ...

Weak diurnal driven upslope flow, enhanced by alpine pumping sneaks beneath weak to moderate N-erly mid/upper flow. Rich BL is present and persists trough the forecast with deepening BL moisture along the complex orogrpahy.

Forecast soundings show mostly capped conditions for the lowlands, but a temporarily weakly or uncapped environment for the afternoon into the evening. MUCAPE in the 1500 to 2000 J/kg range meets weak shear at all levels although some improving anvil-layer shear evolves during the afternoonn in response to 40 kt N-erly winds at 300 hPa. ECAPE could be lowered somewhat with rather dry mid-levels but still enough CAPE for robust updrafts is anticipated.

Scattered afternoon thunderstorms evolve along the orography and remain more or less quasi-stationary for some time, before downdrafts/local cold pools induce some erratic foreward motions. Heavy rain becomes one issue on a local scale with hail also well possible. Even an isolated large hail event is not ruled out but this threat is driven on the storm-scale. Severe downburst gusts are also forecast with high based thunderstorms atop a well mixed BL and with dry air entrainment from the mid-tropospheric layers. These strong to severe downdraft winds could also outrun the thunderstorm activity itself and hence the level 1 was partially expanded beyond the lightning areas.

... Other lightning areas...

Parts of the Balkan States see another round of diurnal driven slow moving convection with isolated instances of heavy rain, hail and strong downdrafts. Initially stationary thunderstorms spread W/E during the evening hours before encountering a stronger cap. A low-end level 1 was considered but expected manageable time-frame for any severe and isolated coverage of potential instances preclude a level 1 for now.

Far NW Europe will see some elevated overnight convection without producing anything severe and convection over SW Russia experiences too marginal CAPE for any severe threat. Same for Spain with some afternoon/evening convection along the orogrpaphy.