Storm Forecast
Valid: Sun 01 Jun 2025 06:00 to Mon 02 Jun 2025 06:00 UTC
Issued: Sat 31 May 2025 22:24
Forecaster: PUCIK
A level 2 was issued across N Spain mainly for large to very large hail and damaging wind gusts.
A level 2 was issued across S-central France to NW Switzerland mainly for large to very large hail and damaging wind gusts.
A level 1 was issued from Spain through France into Germany, Austria, Switzerland, Poland, Czechia and Slovakia mainly for large to very large hail and severe wind gusts.
A level 1 was issued for Denmark mainly for severe wind gusts and large hail.
A level 1 was issued across Romania mainly for heavy rainfall and large hail.
A level 1 was issued across Russia mainly for severe wind gusts and large hail.
A level 1 was issued across Turkey for heavy rainfall.
A level 1 was issued across Caucasus mainly for large to very large hail and heavy rainfall.
DISCUSSION
... N Spain ...
Ahead of a deep trough over the Atlantic, a cold front is forecast to progress towards the area, undercutting very warm airmass across northern Spain by the evening hours. Combination of orography and warm air riding over the cooler air advected from north will be the lifting mechanisms in this case. Q-vectors suggest strong warm-air advection regime setting up across the area towards the evening hours.
Within a belt of enhanced low-level moisture, MLCAPE of around 1000 J/kg is simulated by the models, with rather skinny CAPE in the upper troposphere.
Strong vertical wind shear is forecast across the whole region, increasing towards W. Across W fringe of the Lvl 2, 0-6 km bulk shear of well above 25 m/s is simulated, along with strongly curved hodographs. Convective coverage is uncertain here, but any sustained storm here will become strongly rotating supercell with threats of large to very large hail and damaging wind gusts. Further E, shear will be slightly weaker, but initiation is more certain. Expect a combination of supercells and linear segments capable of large to very large hail and severe wind gusts as well. Storms will become elevated as they travel NE and encounter progressively cooler air near the ground. Threat of very large hail may be mitigated to some degree by skinny CAPE profiles in the upper troposphere, while severe wind gust threat will be reduced by the storms turning elevated in the late evening to night.
... Southern France to Switzerland ...
As the cold front approaches Massif Central, a convergence zone will setup over the higher terrain and quickly trigger numerous storms in the afternoon hours. This is consistently shown by all of the inspected models. While all the high-resolution models show isolated initiation at first, some produce upscale growth towards the evening.
Storms will form in an environment of 1000 to 2500 J/kg of MLCAPE combining with 15 to 25 m/s of 0-6 km bulk shear and curved hodographs strongly supportive of right-moving supercells. Any supercell will pose a risk of large to very large hail and severe wind gusts. Risk of extremely severe wind gusts may develop in case a large cluster of storms forms and moves over a relatively drier area towards Switzerland, though this scenario is highly questionable. Lvl 2 has been expanded there in case this scenario unfolds. Besides the evening MCS risk, w and N Switzerland is likely to see a formation of supercells as well with attendant hail and wind risk.
Across SW France, elevated storms capable of large hail and heavy rainfall will arrive from Spain in the late evening to night hours.
... Germany, Austria, Czechia, Poland, Slovakia ...
Remnants of overnight convection will likely travel from Germany to Czechia and Poland in the morning hours and may serve as focus for the early afternoon convective initiation. Other potential triggers for the storms will be a weak cold front across Germany and local orography across the area. Overall, convective initiation will be rather easy across the whole highlighted Lvl 1 area.
Moderate MLCAPE values from 1000 to 2000 J/kg are forecast across the warm sector with 0-6 km bulk shear between 15 and 20 m/s and slightly higher values towards the cold front in Germany. A mix of linear segments and supercells is forecast across the whole area, posing risks of large hail and severe wind gusts. Stronger supercells may be capable of very large hail. The activity may easily persist into late evening or early night hours.
As of writing the forecast it was difficult to denote an area of higher severe weather risk that would match Lvl 2. However, within the broad Lvl 1 issued, it is expected that one or two corridors of higher severe weather risk will develop and these may be better apparent in the morning hours.
... Denmark to SW Sweden ...
Storms will initiate across Denmark in response to the cold front passage and quickly move towards Sweden in strong mean flow in the troposphere. Over Denmark, surface-based convection is forecast with isolated risk of severe wind gusts and perhaps marginally large hail falling with stronger updrafts. As storms move towards Sweden, strong warm air advection will yield strongly curved hodographs, but also a stable surface layer will be present. This should limit the risk of gusts or tornadoes.
... Romania ...
In weaker shear and weaker mean flow, the main hazard will be heavy precipitation in the topographically rich areas. Large accumulations of hail or marginally large hail may also occur with stronger cells.
... Turkey ...
Heavy rainfall producing storms are forecast in weak mean flow in the core of a pronounced low.
... Caucasus ...
Ahead of an advancing low at mid to upper troposphere, scattered storms will form across the local orography. Given strong shear, supercells can be expected with risks of large to perhaps even very large hail. Coverage of storms will increase overnight with the passage of the low.
... Russia ...
Ahead of a cold front, MLCAPE values of 500 to 1500 J/kg are forecast. Moderate to strong bulk shear is forecast and multi to supercells are anticipated to initiate along the front. Expect a risk of large hail and isolated severe wind gusts.
