Storm Forecast
Valid: Mon 24 Aug 2026 06:00 to Tue 25 Aug 2026 06:00 UTC
Issued: Sun 23 Aug 2026 21:16
Forecaster: PUCIK
A level 3 was issued across NE Spain and S France mainly for large to very large hail and damaging wind gusts.
A level 2 was issued from NE Spain through S and central France towards NW Mediterranean and Liguria mainly for large to very large hail, damaging wind gusts and heavy rainfall.
A level 2 was issued across NW Italy mainly for heavy rainfall and large hail.
A level 1 was issued for France and the Alps mainly for large hail, severe wind gusts and heavy rainfall.
A level 1 was issued from Portugal to NW Spain mainly for tornadoes and heavy rainfall.
A level 1 was issued for Bulgaria and North Macedonia mainly for large hail and severe wind gusts.
DISCUSSION
... NE Spain, France towards Corsica and NW Italy ...
A synoptic-scale trough is forecast to cross the region, with a cold front stagnating across the Iberian penninsula and WAA regime ongoing across France. A complex mesoscale pattern is anticipated, with several convergence zones simulated across Spain and France. Drylines developing owing to the downslope winds will play a significant role both over NE Spain and S France. Furthermore, orography will also act to trigger storms. Large gradients in MLCAPE values are simulated by the models, with local hotspots over both highlighted areas. Here, the MLCAPE will, thanks to a significant overlap of abundant low-level moisture and mid-tropospheric lapse rates exceeding 7 K/km, reach around 2000 J/kg.
From NE Spain to S France, a very strongly sheared environment is forecast, with 0-6 km bulk shear between 20 and 30 m/s, combined with locally strongly curved hodographs where 0-3 km SRH will exceed 250 m2/s2. Such an impressive environment may sustain extremely severe storms capable of very large, perhaps even giant hail, and destructive wind gusts. Both areas have some flies in the soup. First and foremost, the impressive CAPE-shear overlap zone is relatively narrow. In both cases, a strongly right-moving supercell is required to maximize the residence time within it. Over Spain the storms may quickly race towards a lower-CAPE environment over the Pyrenees. Over France, an upscale growth would make the convective system take a more northerly direction towards lower CAPE. Second, morning storms over the Pyrenees may affect the daytime heating over France. Third, Spanish storms may suffer from dry air intrusion at mid-troposphere in the wake of the trough and given very strong shear at that height, this could make the storms suffer.
All these points are raised to signal the following: Both areas have the potential to see extremely severe weather, but neither is a slam dunk.
What seems quite likely is an evolution of a convective system over south-central France with one or more swaths of severe wind gusts. Before that happens, western France may see a mix of multi- to supercells with large to very large hail. As shear weakens towards the north and so does the CAPE, the severe weather potential will weaken as well.
An overnight development is also far from certain: as the trough progresses east, the storms may hug the French coastline and feed on the high CAPE environment over the Mediterranean. High CAPE and strong shear would ensure a high likelihood of severe weather. The storms may continue towards Corsica and Liguria and maintain high intensity. Given the lack of clear mesoscale lift, storm-scale processes will dictate the outcome. An increase in the storm coverage is also forecast over Piemonte, near the Alps, with heavy rainfall and large hail becoming a concern with late-night and early-morning storms.
... Portugal to W Spain ...
The proximity of the surface low slowly shifting north/northeast will result in a strong flow in the lower troposphere. Due to the friction, strong low-level shear is forecast with values of 10 to 15 m/s in the bottom 0-1 km layer. Furthermore, strongly curved hodographs are simulated with 0-500 m SRH values of 100 to 200 m2/s2. Combined with low LCLs, the environment will support tornadoes in supercells. Skinny CAPE and warm, very moist profiles with low ELs and insignificant mean flow will limit other hazards, perhaps beyond heavy rainfall.
... Bulgaria to North Macedonia ...
Orographically driven scattered storms are forecast in the afternoon hours. With moderate shear allowing for some longer-lived multicell clusters, higher LCL environment combined with high CAPE will allow for isolated large hail and severe wind gusts.
