Torrential rainfall for north Italy, northwest Slovenia, northwest Croatia in the next 24 hours
A cutoff low will push across the northern Mediterranean / southern Alpine region today. Combined convective and orographic rainfall is expected, with peak 24h cumulatives locally above 100 mm.
Strong southerly winds will advect warm, moist airmass northwards into the region. Expect moderate to locally strong instability to develop, with 1000-2500 J/kg MLCAPE. Strong 30-50 kt mid-level (500 mbar) southwesterly flow will combine with the southerly to southeasterly low level flow to produce a strongly sheared environment with up to 50-60 kt deep-layer shear. Expect severe thunderstorms across the northern Adriatic region, with pre-frontal isolated/discrete supercells, and a squall line with embedded/training supercells in the afternoon (Sunday). Main threats will include torrential rainfall, severe straight line winds and [mesocyclonic] waterspouts which may make landfall along the coast of NE Italy, SW Slovenia and NW Croatia.
Strong southerly low level flow will translate into strong upslope flow on the southern slopes of the Alps and western slopes of the Dinarides, producing additional orographic rainfall. Totals until midday on Monday (local time) will locally exceed 100 mm. Expect local flooding, potentially very significant in the narrow valleys of the southern Alps and western Dinarides.