Storm Forecast
Valid: Mon 23 Jun 2025 06:00 to Tue 24 Jun 2025 06:00 UTC
Issued: Sun 22 Jun 2025 22:46
Forecaster: PUCIK
A level 2 was issued across parts of SE France mainly for large to very large hail and severe wind gusts.
A level 2 was issued from NE Switzerland through Austria into Czechia, Poland and W Slovakia mainly for damaging wind gusts and large hail.
A level 1 was issued across Denmark, S Sweden, N Poland mainly for severe wind gusts.
A level 1 was issued across Portugal, N Spain and S France mainly for large hail and severe wind gusts.
A level 1 was issued across SW Russia mainly for tornadoes.
DISCUSSION
... N Switzerland to SE Germany, Czechia, Slovakia, Poland ...
A complex and potentially dangerous severe weather situation is forecast to evolve across the area ahead of a developing frontal wave. Strong unidirectional shear profiles are simulated all over the warm sector with shear confined especially to the bottom 3 km. 0-3 km bulk shear between 15 and 25 m/s and 0-1 km bulk shear of 10 to 15 m/s is forecast. While the mid-tropospheric lapse rates will not be particularly steep, mixing ratios of 12 to 14 g/kg will allow for 1000 to 2000 J/kg of MLCAPE by the late afternoon hours. Forecast profiles and hodographs suggest an elevated risk of large hail and damaging wind gusts with supercells and linear segments that could be long-lived and long-tracked given the degree of the vertical wind shear and the fast storm motion. Risk of severe wind gusts will increase further east into the areas with very hot airmass and deep boundary layer experiencing substantial day time heating.
Considerable uncertainty remains with the forecast though:
1/ Degree of early morning convection
This will be important for the western half of Lvl 2. If too many storms develop early over Bavaria and western Czechia, these regions may at risk from the lack of airmass recovery. Fast easterward motion of clouds gives chances for quick clearing after any developing storms though.
2/ Convective mode
It is uncertain if isolated mode will dominate or if storms quickly congeal into a quasi-linear convective system and there is a large disagreement among the convection-allowing models. Currently, models do not show a pronounced lift across the cold front early on and the storms will quickly move away from the zone of the mesoscale lift. Most likely evolution is that first, isolated supercells form with threat of severe wind gusts and large to very large hail. The highest risk of very large hail will be over SE Germany to NW Austria with the highest CAPE values in the upper troposphere. Towards the late afternoon or evening hours, as storms moves east into profiles more favourable for strong cold pools and the cold front accelerates, an upscale growth to at least one linear segment. Then, a transition into damaging wind gusts as primary threat is expected.The exact track of the damaging wind gust producing storms is unknown at the moment and there is a considerable risk of this scenario all the way from S Poland through Czechia and Slovakia to SE Austria.
Storms will rapidly spread eastwards during the day and evening hours. 0-1 km shear is forecast to increase towards the evening hours and the LCLs will decrease. Should supercells persist still at that time, there will be a risk of tornadoes as well.
... NE Italy ...
Lvl 2 has been expanded over this region, where high-resolution convection allowing models show development of intense storms as the cold front approaches and storms spread from the Alps towards the lowlands. While 0-6 km bulk shear will not be extremely strong, a couple of supercells with large to very large hail and severe wind gusts are possible.
... Massif Central to French Alps ...
A regional hotspot in severe storms is expected over here. Orography will provide a mesoscale lift. Isolated storms will form in an environment of MLCAPE around 2000 J/kg, 0-3 km bulk shear of around 15 m/s and high LCLs. Large to very large hail and severe wind gusts will be possible with the most intense storms.
... Denmark to Sweden, NE Germany and NW Poland ...
Scattered to widespread storms will form ahead of a fast-moving short-wave trough and the rapidly advancing cold front. Several linear segments may form with threat of severe wind gusts given strong mean flow and 0-3 km bulk shear of up to 15 m/s.
... N Spain ...
Isolated to scattered storms are forecast in an environment of MLCAPE around 1500 J/kg and 0-6 km bulk shear of around 15 m/s. More intense updrafts can become transient supercells with risks of large hail and severe wind gusts.
... Portugal, W/NW Spain ...
A highly uncertain scenario is forecast across the area ahead of a low over the Atlantic. Strongly sheared environment will combine with steep mid-tropospheric lapse rates that had been advected from central Iberia. ICON-EU shows some profiles that would be suggestive of intense supercellular development, but ECMWF or GFS stay more conservative regarding the development with high values of CIN and high LFCs. The most likely scenario currently is that some elevated storms form in the late evening to overnight hours. Large hail will remain a risk given strong effective shear and at least modest CAPE through the upper troposphere.
... SW Russia ...
A pocket of higher SRH and stronger low-level shear is forecast with numerous storms developing ahead of a pronounced short-wave trough. As the enhnaced low-level shear combines with low LCLs, tornadoes are possible.
