Storm Forecast
Valid: Wed 26 Aug 2026 06:00 to Thu 27 Aug 2026 06:00 UTC
Issued: Tue 25 Aug 2026 20:42
Forecaster: PUCIK
A level 2 was issued across France for large to very large hail, severe wind gusts, and tornadoes.
A level 2 was issued across extreme N Spain for large to very large hail and severe wind gusts.
A level 1 surrounds level 2 for same threats but lower coverage and overall lower intensity.
A level 1 was issued for N Portugal to NW Spain mainly for tornadoes and heavy rainfall.
A level 1 was issued for Romania mainly for heavy rainfall and marginally large hail.
DISCUSSION
... France ...
A short-wave trough at mid to upper troposphere will eject over the region from Spain, crossing the area from late afternoon to night hours. Closer to the surface, a frontal wave will pass from the Bay of Biscay towards the SE UK. A warm front will cross central to northern France, while a cold front will approach from the west in the evening hours. The cold front will serve as a primary trigger for storms with its anabatic circulation. The majority of storms are forecast to develop in the wake of the surface cold front. A modest overlap of low-level moisture and steep mid-tropospheric lapse rates will exist along the cold front, with deeper low-level moisture in the wake of the front. MLCAPE/MUCAPE will increase from northwest to south with values ranging from 800 to 3000 J/kg across the Lvl 2. At the same time, a strongly sheared environment is forecast with 20 to 30 m/s of 0-6 km bulk shear and 0-3 km SRH locally exceeding 300 m2/s2. Locally and especially near the warm front, strong low-level shear and low-level helicity are simulated. The strength of deep-layer shear will also increase from north to south.
A mix of hazards is forecast with well-organised storms developing along the front and in its wake. Initiation will become more uncertain over S France, where the best CAPE/shear overlap will exist. Risk of very large hail will increase towards the south, where fat CAPE profiles are simulated, and storms may remain more isolated. Damaging wind gusts will be most likely where storms cluster, which would be along the cold front in W France. Tornado risk is more likely in lower LCL and stronger 0-1 km shear environment along and south of the warm front. Models are not in complete agreement concerning low-level stability and how many storms will be surface-based as the low-level shear increases in the evening. Especially over NW France, a large fraction of the storms may be elevated, riding the cool side of the frontal wave. Still, they may bring large to very large hail and severe wind gusts.
... extreme N Spain ...
A very strongly sheared environment will be present over N Spain, with 0-6 km bulk shear up to 35 m/s and 0-3 km SRH exceeding 300 m2/s2. Such a kinematic setup could support intense supercells. MLCAPE around 1000 J/kg is forecast by models, with initiation provided by mountains. There is a question of how sustained the storms will be as they blow through the mesoscale lift mechanism very quickly. Should a supercell form here, expect large to very large hail combined with damaging wind gusts. But there is a chance updrafts will not make it, as they escape the initiation zone too fast in very fast mean wind of 20 m/s.
... N Portugal to NW Spain ...
Cold front will sweep across the area with 15 to 20 m/s lower tropospheric flow in the warm sector and curved hodographs. Moist profiles with low LCLs combined with substantial low-level shear point to an elevated tornado threat. Model soundings reveal that lower tropospheric stability may be a problem, especially further inland. Therefore, tornado risk is conditional on more substantial low-level SBCAPE being present. Besides tornadoes, local heavy rainfall event may occur with skinny CAPE profiles and low LCLs, should several cells pass over the same location.
... Romania ...
In northwesterly flow aloft, poor lapse rates, combined with modest low-level moisture will result in skinny CAPE profiles. 10 to 18 m/s of 0-6 km bulk shear are forecast with straight hodographs, suggesting multicells and some transient splitting supercells. Heavy rainfall and some large hail will be the main threats. Heavy rainfall will be most likely in the Carpathian area and along weak frontal boundary across the northern part of the highlighted area. More isolated mode is anticipated towards the lowlands.
