Storm Forecast
Valid: Sat 31 May 2025 06:00 to Sun 01 Jun 2025 06:00 UTC
Issued: Fri 30 May 2025 21:16
Forecaster: PUCIK
A level 2 was issued across N France, S Belgium, Luxembourg, W-central Germany mainly for large to very large hail, severe wind gusts and to the lesser extent for tornadoes or heavy rainfall.
A level 1 was issued from central France through NW Switzerland, S Germany into E Germany, Czechia and SW Poland mainly for large hail and severe wind gusts.
A level 1 was issued across Pyrenees mainly for heavy rainfall and large hail.
A level 1 was issued across NW Italy mainly for heavy rainfall and large hail.
A level 1 was issued across NE Slovakia, SE Poland and NW Ukraine mainly for marginally large hail.
A level 1 was issued for Crete, W Turkey, SE Ukraine mainly for heavy rainfall.
A level 1 was issued for Cyprus for large hail and severe wind gusts.
A level 1 was issued for NE Turkey and Caucasus for large hail and severe wind gusts.
A level 1 was issued for N Russia mainly for severe wind gusts and to the lesser degree for tornadoes.
A level x was issued across (areas) for (hail|tornadoes|wind gusts|extreme rainfall). (repeat for each level area)
DISCUSSION
... N France through Belgium, Luxembourg into Germany ...
Within the warm sector in between of a diffuse cold front slowly arriving from W France and a warm front across northern Germany, a belt of dewpoints of 16 to 18 deg C is forecast, overlapping with moderately steep lapse rates up to 7 K/km. South of the belt, deep dry boundary layer with abundant heating are simulated, resulting in Inverted-V profiles from central France through Switzerland into S Germany. MLCAPE values from 1000 to 2500 J/kg are forecast within the belt of enhanced low-level moisture. Multiple rounds of storms are likely across the area.
The first round of storms will be tied to a short-wave trough entering area around 09 UTC. Convective initiation will likely be ongoing towards 12 UTC, starting from an area of elevated showers that will move over progressively warmer and destabilized airmass. The most likely point of initiation will be extreme W Germany with storms spreading E/ESE. With 0-6 km bulk shear of 15 - 20 m/s, storms will be organised into transient supercells and short linear segments. Expect threat of severe wind gusts and large hail. Threat of severe gusts will increase if the storms propagate SE towards the deeper boundary layer environment. Evolving convective system may reach Czechia and southwestern Poland.
The second round of storms may follow in the evening hours with arrival of a second short-wave trough and finally also the cold front. Some models suggest slight increase in the deep layer shear with values around 20 m/s and multiple splitting supercells evolving across the area with threats of large to very large hail and severe wind gusts. With slight increase in low-level shear towards the evening hours, a tornado will be possible especially in case of a favorable interaction of individual storms. Storms may last well into the night and early morning hours as the cold front slowly moves across the area.
... SE Germany, Czechia, SW Poland ...
Same as in the area above, two rounds of storms are possible across the domain. The first round will be tied to the initiation over the orography with storms spreading towards SE and the lowlands. The second round of storms will be tied to the development across W Germany and the eventual upscale growth of a cluster of storms arriving from this area. CAPE - shear parameter space will be favourable for isolated severe convective storms. Bulk shear of 10 to 15 m/s is forecast in the 0-6 km layer, increasing towards N. Mostly multicells are forecast with a transient supercell not ruled out especially over S Poland/N Czechia. Isolated large hail and severe wind gusts are forecast.
... Pyrenees, central France ...
Isolated to scattered convective initiation is forecast across the higher terrain. Strong heating will yield Inverted-V profiles and with 0-6 km bulk shear around 10 m/s, at least marginal convective organisation can be expected. Isolated severe wind gusts and large hail may accompany stronger storms. Across Pyrenees, heavy rainfall may occur as well.
... NW Italy ...
Upslope flow will result in a convective initiation across the mountains. While shear will remain rather marginal, CAPE profiles suggest threat of large hail. Given slow storm motion, isolated heavy rainfall events are also possible.
... NE Slovakia, SE Poland, NW Ukraine ...
A very marginal Lvl 1 is introduced over the area ahead of a weak cold front. Environment will be characterized by skinny CAPE profiles and 0-6 km bulk shear of up to 15 m/s. Some well-organised storms are possible and despite the skinny CAPE, produce hail of 2-3 cm in diameter. Heavy rainfall threat will be diminished by the faster storm motion and severe wind gust threat by the low LCLs.
... N Russia ...
Ahead of an advancing cold front and south of a stalling warm front, moderate to strong unidirectional shear is forecast combined with MLCAPE values of up to 1000 J/kg. Linear segments are forecast to develop with isolated severe wind gust threat. Towards the warm front, shear is forecast to increase with spots of 0-1 km bulk shear exceeding 10 m/s. While forecast hodographs remain straight, tornado threat will be enhanced over this area.
... SE Ukraine, S Russia ...
Skinny CAPE profiles and slow storm motion combine into heavy rainfall threat with any developing storms. Storms will be short lived and their activity will quickly diminish after the sunset.
... W Turkey ...
Same as over Ukraine, skinny CAPE profiles and slow storm motion will yield an enhanced risk of heavy rainfall.
... Cyprus ...
A difficult forecast to make for the area. A strong synoptic-scale lift will overspread the island contributing to the development of MLCAPE of around 500 J/kg. At the same time, strong vertical wind shear with 0-6 km bulk shear exceeding 25 m/s is simulated by all the models. So a potential will exist for supercells to develop with threats of large hail and damaging wind gusts. Initiation is questionable though with some models indicating persisting CIN and rather high LFC. Will maintain a Lvl 1 and the convective evolution over the area needs to be closely monitored.
... NE Turkey to Caucasus ...
Steep lapse rates combined with 0-6 km bulk shear exceeding 15 m/s will result in an enhanced threat of large hail with stronger storms. Across Turkey, Inverted-V profiles further inland will also result in a threat of severe wind gusts.
