Storm Forecast
Valid: Sun 27 Jul 2025 06:00 to Mon 28 Jul 2025 06:00 UTC
Issued: Sat 26 Jul 2025 21:56
Forecaster: PUCIK
A level 3 was issued across N Romania, N Moldova and S Ukraine mainly for very large hail, damaging wind gusts and tornadoes.
A level 2 was issued across Serbia to SW Romania mainly for large to very large hail and damaging wind gusts.
A level 2 was issued across Ukraine mainly for severe wind gusts, heavy rainfall, tornadoes and large to very large hail.
A level 2 was issued across Hungary, Slovakia, extreme northeastern Czechia and southern Poland mainly for heavy rainfall.
A level 2 was issued across the Adriatic Sea and the adjacent coastlines mainly for large to very large hail and heavy rainfall.
A level 1 was issued across N Italy and W Slovenia mainly for heavy rainfall and large hail.
A level 1 was issued across Switzerland, parts of eastern France, Austria, Croatia, Slovenia mainly for heavy rainfall.
A level 1 was issued across Sweden for heavy rainfall.
A level 1 was issued across W Estonia and N Latvia mainly for heavy rainfall.
DISCUSSION
... Serbia to Romania and Ukraine ...
An outbreak of severe storms is likely across the region. The situation is dictated by a wavy cold front and an advancing mid to upper tropospheric trough. The trough will swing from Serbia through Romania into Ukraine, providing synoptic-scale lift. Ahead of the trough, strongly-sheared environment will overspread the frontal zone and the warm sector. Initiation of the storms will be secured by the frontal boundary and the local orography. Several waves of storms are possible. The limitation of this forecast stems from the uncertainty of the overnight and morning storm activity, which should be abundant, especially over W Romania.
Storm coverage will begin increasing after 9 UTC over Serbia, where moderate MLCAPE of around 1000 J/kg will combine with 20 to 25 m/s of 0-6 km bulk shear. With majority of CAPE above -10 deg C, supercells will be capable of large to perhaps even very large hail, locally combined with severe wind gusts. There will be a potential for upscale growth as storms move towards Romania.
Across Romania, isolated development ahead of the band of storms from Serbia will be possible along the front itself and the mountains. A dryline will setup between the hot airmass with steep lapse rates over the southeast of the country and the moist airmass close to the front. Here, in this belt, fat CAPE profiles with MLCAPE exceeding 2000 J/kg are forecast. This belt of higher CAPE will reach into S Ukraine and N Moldova. Curved hodographs with 15-25 m/s of 0-6 km bulk shear and 0-3 km SRH of locally exceeding 300 m2/s2 will support long-lived supercells and linear segments. All severe weather hazards will be possible, including very large hail, damaging wind gusts, heavy rainfall and tornadoes as the storms travel to Ukraine. Dominant severe weather type will come down to the convective mode (either supercells or a bow echo or both), which is uncertain at the moment.
Tornado risk will peak between 15 and 18 UTC in between of N Romania and S Ukraine, when still enough SBCAPE will be present and the 0-1 km bulk shear exceeds 10 m/s with 0-1 km SRH locally exceeding 150 m2/s2. While low-level shear will increase further into the night, storms will likely start turning elevated as they travel further north into Ukraine. The main threats will be heavy rainfall/severe wind gusts with large hail possible in case that supercells remain part of the convective mix. Level 3 is issued for the most likely corridor of extremely severe weather, but note that the morning development may shift the corridor compared to the expectations.
... Poland, NE Czechia, Slovakia, Hungary ...
Within the core of the trough, the mid-tropospheric flow will decrease compared to the previous day. Strong synoptic-scale forcing will moisten the profiles, yielding extremely easy convective initiation. Skinny CAPE profiles with low LCLs will yield efficient warm rain processes. Combined with weak mean flow, it will be easy for storms to produce 1h accumulations of 50 mm or even higher locally. Models agree on the widespread nature of the storms, which results in a Lvl 2 for heavy rainfall. Across southeastern Poland, stronger low-level shear may yield a tornado or two in the late afternoon hours.
... Northern Italy to western Slovenia and northwestern Croatia ...
While the vertical wind shear will not be the strongest during the day, fat CAPE profiles are simulated across the area and scattered to widespread initiation on the mountains with storms spreading southward with time. Expect a combination of large hail and heavy rainfall risk. An approach of another short-wave trough from northwest will keep the storms going till the morning hours. As the trough approaches, 0-6 km bulk shear is forecast to increase, which will also increase the risk of supercells in the night hours. Then, there is a higher chance for severe wind gusts, as well as very large hail. Supercells are forecast to move off the Apennines towards the Adriatic sea.
... Germany, Switzerland, E France ...
Mean wind of around 5 m/s combined with low LCLs and skinny CAPE profiles will yield local heavy rainfall events across the area. The highest risk is expected over the mountains of Switzerland, where upslope flow will yield likely more waves of showers and storms, plus the strongest synoptic-scale lift is forecast here.
... Sweden ...
Continuous weak southerly upslope flow will have a chance to yield several rounds of showers/thunderstorms throughout the day. Given moist profiles, low LCLs and deep warm cloud depth, developing cells will be efficient heavy rain producers. Local flash flood event is thus possible.
... W Estonia, N Latvia ...
Sea breeze will initiate scattered storms throughout the day. Forecast profiles show skinny CAPE combined with low LCLs and mean wind close to 0. This will result in a possibility of a few local heavy rainfall events.
