Storm Forecast
Valid: Sat 18 Jul 2026 06:00 to Sun 19 Jul 2026 06:00 UTC
Issued: Fri 17 Jul 2026 16:36
Forecaster: TUSCHY
A level 2 was issued for parts of NE Italy into the NW Balkans for large to very large hail, severe gusts and heavy rain.
A level 1 surrounds the level 2 with similar hazards but lowered probabilities.
A level 1 was issued for SE Finland and S Sweden mainly for heavy rain.
A level 1 was issued for parts of E Spain mainly for isolated large hail, severe gusts and heavy rain.
SYNOPSIS
The long-lived blocking ridge breaks apart as strong height falls over Scandinavia spread S. Residual ridging over the CNTLR Mediterranean and ridging into E Europe keep parts of S/SE Europe hot and stable.
DISCUSSION
... NE Italy to Slovenia into Croatia and parts of Bosnia and Herzegovina/Serbia ...
A brisk westerly flow regime with a gradual decrease in geopotential heights and with numerous weak/progressive low-amplitude waves affect the area of interest for most of the day.
Most of the unstable airmass remains beneath synoptic-scale subsidence with some lift along the S Alps. The main focus for CI resides along the periphery of an approaching frontolytic cold front, which aligns from NE Italy into the Balkans. A broad/diffuse confluent BL wind regime results in additional lift and increases confidence in CI.
The sweetspot with best CAPE/shear overlap exists from NE Italy to Slovenia, Croatia into N/W Bosnia and Herzegovina with DLS in the 15-20 m/s range. Forecast hodographs feature straight signatures with HP-style cell signatures. Hence expect active cell splitting with growing small-scale clusters. Any more discrete and deviating cell however can rotate, increasing the large hail risk. This messy picture features a compact swath with a more focused (large) hail, severe gust and heavy rain risk - enough for upgrading to a level 2.
A separate level 2 was added for E Emilia-Romagna and far S Veneto, where onshore moving sea breeze fronts (or dried downslope wind from the Apennines) could break the weak cap. MUCAPE up to 4000 J/kg and impressive shear favor a few supercells with very large hail, severe gusts and heavy rain.
Both level 2 areas were merged over the N Adriatic Sea to highlight the risk of numerous offshore moving multicells and supercells with all kind of hazards. The level 2 was expanded into N Serbia to account for a progressive cold pool driven severe MCS event, growing upscale from mentioned convection.
Within the surrounding level 1, numerous intense updrafts will produce severe events like large hail, severe gusts and heavy rain, but no clear focus for maximized coverage is seen in latest NWP data. Hence no upgrading.
... E Europe to S Scandinavia ...
The level 1 was expanded far E/NE towards the Baltic States admits a N-ward fanning plume with roughly 1000 J/kg MUCAPE and adequate shear / hodograph curvature for a transient risk of rotating cells with hail (isolated large), strong to severe gusts and heavy rain.
S Finland will see a tightening warm front/improving isentropic ascent with embedded convective elements admits 500 J/kg CAPE in lowest 5km AGL. WAA driven curved hodographs support transient rotating updrafts, mainly boosting rainfall rates with local flash flooding possible.
... E-CNTRL France to Switzerland and S Germany ...
Diminished BL moisture but still adequate shear for transient updraft rotation support a risk for a multicell/isolated supercell mix. Hail, strong gusts and heavy rain will be the main hazard.
... S Sweden ...
Placed beneath the upper trough with some wrap-around moisture approaching from the E, expect numerous slow moving thunderstorms with heavy rain and a few events with lots of small hail/gusts. Isolated flash flooding is possible.
... E Iberia ...
Anticyclonic mid/upper flow regime persists with virtually no noteworthy thickness change during the day. Onshore flow of an extremely moist marine airmass with 2m dewpoints in the mid to upper twenties (driven by positive 3-4K SST anomalies) advects beneath a stout African/Spanish EML plume. This offers MUCAPE in the 3000-5000 J/kg range and a textbook-style loaded gun situation with ongoing capping. We cannot rule out a few mountain storms due to upslope advected moisture into the capped area or due to passing weak/transient synoptic waves from the W. A dry 650 hPa layer could hamper growing updrafts with effective entrainment but any maturing updraft would then grow into a more humid layer above 600 hPa. EPS/ENS data gives enough QPF signals (medium/maximum) along the orography for adding a confined level 1 due to large hail/severe gusts and heavy rain - on a local scale.
