Storm Forecast
Valid: Sat 02 Aug 2025 06:00 to Sun 03 Aug 2025 06:00 UTC
Issued: Fri 01 Aug 2025 22:30
Forecaster: PUCIK
A level 2 was issued across N Italy mainly for large to very large hail, severe wind gusts and to the lesser degree for heavy rainfall and tornadoes.
A level 2 was issued across E Slovenia, NW Croatia and SW Hungary mainly for large hail, severe wind gusts and heavy rainfall.
A level 1 was issued across N Italy, Croatia, S Austria and W Hungary mainly for large hail, severe wind gusts and heavy rainfall.
A level 1 was issued across S Germany, Switzerland and NW Austria mainly for heavy rainfall.
A level 1 was issued across Austria, E Czechia, W Slovakia and S Poland mainly for heavy rainfall, severe wind gusts and to the lesser degree for large hail.
A level 1 was issued across E Spain mainly for large hail and severe wind gusts.
A level 1 was issued for E Algeria and Tunisia mainly for large to very large hail and damaging wind gusts.
A level 1 was issued for Sweden mainly for heavy rainfall.
A level 1 was issued for Finland and NW Russia mainly for heavy rainfall and to the lesser degree for severe wind gusts and tornadoes.
A level 1 was issued for S Turkey mainly for severe wind gusts and heavy rainfall.
A level 1 was issued across E Black Sea and Georgia and Caucasus region mainly for large hail and heavy rainfall.
DISCUSSION
... N Italy ...
A short-wave trough will already start crossing the NW part of the country in the early morning hours with abundant thunderstorm activity around the Alps and Liguria. Heavy rainfall and some large hail are possible with stronger updrafts. The activity will swing E during the day with the most active period from 9 to 15 UTC, after that the short-wave trough will have passed towards Croatia, Slovenia and Austria. From 9 to 12 UTC, as a surface low develops south of the Alps, southerly wind component in the surface wind will set up a dryline near the Apennines. North of the dryline, MLCAPE around 1500 J/kg is forecast to combine with around 20 m/s of 0-6 km bulk shear. High-resolution models point at a high risk of supercells developing over southern Veneto and Emilia Romagna regions. A mix of large to very large hail, heavy rainfall and severe wind gusts is expected. Severe wind and very large hail threat will be mitigated to some degree by low LCLs. A tornado risk may develop with supercells passing over the dryline, which may act as a vorticity source. Storms will then spread over the Adriatic Sea towards Croatia.
Much more questionable is the activity in the late afternoon behind the trough over NW Italy. While CAPE/shear parameter space will remain at least modestly conducive to severe storms, initiation is uncertain with some drying noted around the mid-troposphere due to the subsidence. Decided to keep the area in Lvl 1 for large hail and isolated severe wind gusts in case some storms manage to develop over the mountains and persist as they move towards the lowlands.
... Croatia, Slovenia, S Austria, SW Hungary ...
Second corridor of enhanced severe weather risk is forecast in this area. Potentially negative factor may be the morning storms across Italy with lingering clouds and rainfall limiting the daytime heating. Lower resolution models show very similar environment to northern Austria or Slovakia, with about 1000 J/kg of MLCAPE and 10 to 15 m/s of 0-6 km bulk shear. Higher resolution models show stronger shear in the Lvl 2 corridor and also updraft helicity swaths representing potential supercell tracks. Expect enhanced large hail and severe wind gust threat here compared to the north. For this reason, Lvl 2 is issued over the area. Rather unimpressive shear/CAPE profiles will limit the chances for extremely severe phenomena.
... Austria to E Czechia, W Slovakia and S Poland ...
Scattered to widespread storms are forecast over the region. Much of the activity is forecast in the wake of the cold front that will move E during the day, especially after a wave develops over the Alps and the cold air surges in its wake to the east and southeast. The highest chance of severe weather will be shortly after 12 UTC to the north of the Alps, where ahead of the front, curved hodographs will overlap with up to 15 m/s of 0-6 km bulk shear may allow for a supercell to develop with large hail and severe wind gust threat. As storms cluster around the front, one or two systems may form, travelling north towards Poland. Severe wind gusts will be the dominant threat in the warm sector, maximized as the low-level flow ramps up in the evening hours, while heavy rainfall will dominate behind the frontal wave in the west and also in the overnight hours with training of elevated storms possible over certain areas.
... N Switzerland, S Germany, NW Austria ...
Forecast profiles reveal moist conditions with very low LCLs and CAPE concentrated in the warm part of the cloud, combined with weak mean wind. There will be an isolated threat of heavy rainfall even with unelectrified showers.
... W Spain ...
A dryline is forecast to setup over the area with an upslope moist flow from the sea and dry air present over the inland. Models diverge heavily in terms of whether initiation is possible with ICON-EU showing profiles without any CIN and dry layers. ECMWF based profiles look more questionable. With moderate shear and MLCAPE values exceeding 1500 J/kg, sustained storms will be capable of large hail and also severe wind gusts. Wind gust risk will be higher further inland where boundary layer is deeper.
... North Africa ...
Long hodographs featuring 0-6 km bulk shear of around 25 m/s will overlap with solid MLCAPE values between 1000 and 2000 J/kg and high LCLs, yielding high conditional probability of severe weather given that initiation can occur. While initiation and coverage is uncertain, any storm that forms between E Algeria and Tunisia will be capable of becoming supercell capable of large to very large hail and damaging wind gusts.
... Sweden ...
A short-wave trough will move across the area from E to W. At the same time, a stalling frontal boundary is forecast with moist airmass along and to the north of it. Profiles reveal easterly mean flow parallel to the front and moist conditions with low LCLs and large fraction of CAPE in the warm part of the cloud. Expect heavy rainfall to be the dominant threat with storms as they spread N during the day with slow movement of the front.
... Finland and NW Russia ...
Similar to Sweden, bottom heavy CAPE profiles with low LCLs are forecast with tendency for storms to produce heavy rainfall. Towards E, regions with enhanced 0-1 km bulk shear and also higher LCLs over Russia imply presence of marginal tornado and severe wind gust risk.
... E Black Sea, Caucasus and Georgia ...
A short-wave trough is forecast to cross the area, providing synoptic scale lift and aiding the development of scattered to widespread storms on the mountains. Profiles reveal moderate MLCAPE, especially over the lowland and 0-6 km bulk shear between 15 and 20 m/s with curved hodographs. At first, supercells with large hail may develop with storms clustering around the mountains later on with heavy rainfall risk taking over eventually.
... W Turkey ...
Extremely warm temperature at the upper troposphere will limit the EL of storms to -20 deg C, which will diminish the risk of large hail and perhaps also lightning activity of the storms. With 10 to 15 m/s of 0-6 km bulk shear, multicells will be the dominant convective type. Given abundant day time heating and deep boundary layer with high LCLs, severe wind gust risk will be dominant one with heavy rainfall as the secondary threat given mean wind locally below 5 m/s.
