Storm Forecast
Valid: Sun 26 Jul 2026 06:00 to Mon 27 Jul 2026 06:00 UTC
Issued: Sat 25 Jul 2026 08:29
Forecaster: TUSCHY

A level 3 was issued mainly for very large hail, damaging gusts and heavy rain. Numerous extreme events are forecast. In addition an intense tornado risk exists.

A level 2/1 surround the level 3 with similar hazards but lowered probabilities.

A level 1 was issued for the W Mediterranean mainly for large hail, severe gusts and heavy rain. An isolated tornado is possible.

A level 1 was issued for parts of Austria mainly for a few heavy rain events.

A level 1 was issued for parts of the Netherlands, Belgium into N/CNTRL Germany mainly for a few gusts and an isolated tornado risk.

A level 1 was issued for parts of W Russia mainly for large to very large hail, severe gusts, heavy rain and an isolated tornado.

SYNOPSIS

The long-lived blocked wave regime over SW into S-CNTRL Europe breaks apart as the formerly barotropic ridge dissolves over/south of Sicily. In the meantime, the stationary upper low W of Iberia shifts E while de-amplifying into a progressive lower amplitude wave with a persistent positive tilt. This wave starts to cut-off from the frontal zone somewhere W of the Tyrrhenian Sea with a more uncertain track more to the S, whereas parts of this energy drift E towards the Balkans as a sharp short-wave trough.

A steering vortex W of Norway takes the frontal zone with a wave into CNTRL Europe, accompanied by a brisk westerly flow regime, whereas a longwave trough over E Europe starts to fill and lift E/NE towards Russia.

This rather complex pattern gets accompanied by eastward progressing fronts over NW into CNTRL Europe and a N-ward moving and intensifying vortex (with cold/warm fronts) over W Russia, all serving as foci for thunderstorm development.

DISCUSSION

... CNTRL Mediterranean ...

This evolving severe event gets accompanied by one of the most impressive parameter space the forecaster has seen for Europe.

Regarding forcing, the main show will be the approaching trough from the W. Its persistent positive tilt creates an unusual tight pressure gradient along its S/SE edge towards the weakening subtropical ridge. The SW-erly winds increase into the 2-3 sigma range for H7-H25, which translates to H7 winds in the 55-70 kt range. The mentioned speed maximum spreads E over most of Italy during the forecast. This puts the DLS into a 25-40 m/s range with 0-3 km shear running a tad lower with 20-35 m/s - values, which are impressive during winter, let alone during peak summer season.

Forecast hodographs show very long and straight signatures, offering very fast storm motions. Increasing BL shear onshore induces stronger hodograph curvature, which not only increases SRH substantially, but also lowers effective storm motions. We therefore expect a very dynamic event with a mix of fast moving, splitting and temporarily back-building convection.

A very moist marine airmass (fuled by the ongoing marine heatwave) with BL mixing ratios in the 16-18 g/kg range/2m dewpoints in the lower to mid twenties spreads NE/N into the approaching wave and the stretched out extensive warm sector, which covers most of Italy. Steep mid-level lapse rates aloft push MLCAPE into the 2000-3000 J/kg range, increasing into the 4000-5000 J/kg range towards the W Tyrrhenian Sea. Combined with the mentioned shear, this creates a volatile background for organized DMC activity with EFI CAPE/shear exceeding +2 SOT.

However we also have to talk about a few caveats, which could impact our forecast. First of all, the wave's positive tilt creates rather diffuse signals for more focused synoptic-scale lift. Ejecting lead waves certainly affect Italy during the forecast with a prolonged period of favorable upper divergence atop the warm sector. NWP guidance however still has some issues with the exact track/timing and strength of those lead waves. Secondly, the warm low-tropospheric airmass due to the wave's tilt keeps a cap alive during the forecast, which is especially true for S Italy during the daytime hours. This however could support more discrete CI, which is not good in such an extreme CAPE/shear background. And thirdly, the wave's WCB offers intense cross-isentropic ascent, which could induce more clouds/elevated convection and hence limited diabatic heating for parts of CNTRL Italy.

Even with those issues, we still expect isolated to scattered CI all day long with various foci like ongoing convection from the previous night (N-Italy), initiation along the orography, along sea breeze fronts or convergence lines or due to augmented frontogenesis along the apex of the wave.

Any thunderstorm has the chance to rotate with all kind of extremely severe possible: very large to giant hail, damaging gusts in excess of 30 m/s and extremely heavy rainfall (and extreme rainfall rates due to the organized nature of the updrafts). In addition, despite the iffy looking BL thermodynamic profile: improving CAPE3 onshore and regionally substantial LL shear next to the mentioned CAPE/shear space add an augmented tornado risk and an intense/damaging tornado event is not ruled out! This risk already starts from 06Z onwards over N-CNTRL Italy.

The level 3 upgrade was most certain over N Italy for the 06Z (ongoing from the previous night) to 15Z period for an eastward passing cluster of (potential tornadic) supercells, growing upsalce into a severe MCS atop the N Adriatic Sea. The second confident upgrade was along the leading edge of the impressive moisture plume, which points towards CNTRL Italy. Numerous discrete supercells are forecast. The southern fringes of the level 3 and 2 areas have lower confident as cap strength dictates the final severe risk.

The level 2 was expanded towards the W Balkans mainly for organized coastal convection during the day but an inland spreading severe risk during the night with all kind of severe possible like large hail, severe gusts and heavy rain next to a tornado threat.

A separate level 1 was added for the W Mediterranean Sea for organized DMC activity. Multicells and a few supercells are possible with all kind of severe, which evolve along a stalling N/S aligned offshore dryline just W of the Balearic Islands. Low thunderstorm coverage keeps this in a level 1 as synoptic-scale subsidence spreads towards the E during the day. A long-lived supercell event is certainly possible however with large hail, severe gusts, heavy rain and a tornado in up to 2000 J/kg MLCAPE and intense shear, which decreases to the N.

... The Netherlands, Belgium into N/CNTRL Germany but also S Germany to Austria ...

A progressive low-amplitude wave approaches the area of interest (Netherlands/Belgium to N/CNTRL Germany) beyond noon while interacting with a plume of better BL moisture. Steepening of the H8-H5 layer lapse rates assists in some low-end 0-4 km CAPE (200-600 J/kg), which spreads E into N/CNTRL Germany. Forecast hodographs reveal long/curved signatures admits 20-25 m/s DLS and 100-150 J/kg SRH3. In addition, the left exit region of a strong upper jet approaches the area and adds improving upper divergence.

Expect increasing thunderstorm coverage from the late afternoon into the overnight hours and lines of organized shallow convection race E/SE. NWP gust signals (also in EPS data) remain reluctant, probably due to moist profiles and weak (D)CAPE. However, strong gusts and graupel will be a risk. In addition, an isolated tornado is possible in this low LCL and improving CAPE3 setup. A broad level 1 was added for this event, where diurnal cycle and some gust imprints in NWP guidance show somewhat better chances for near surface based activity with an isolated tornado risk (combined with a spotty heavy rain risk with merging updrafts). Overall the severe coverage could stay spotty.

Over S Germany into Austria, 400-800 J/kg MUCAPE and weak shear result in scattered slow moving thunderstorms with isolated heavy rain. A level 1 upgrade was performed for parts of Austria, where slow moving and clustering convection poses an isolated heavy rain risk.

...W Russia ...

A structuring depression shifts N and is accompanied by a broad and strongly sheared warm sector. The warm front remains capped with abundant MUCAPE, so very large hail and heavy rain will be the main issue. Further S next to the vortex itself, weakening CIN increases the risk of severe gusts and tornadoes next to large hail and heavy rain. A borad level 1 was issued as some discrepancies with the depression's geometry still exist and hence no clear focus of highest severe probabilities. Regional level 2 conditions are possible.