Storm Forecast
Valid: Wed 15 Jul 2026 06:00 to Thu 16 Jul 2026 06:00 UTC
Issued: Tue 14 Jul 2026 12:10
Forecaster: TUSCHY

A level 3 was issued for parts of N Italy mainly for very large to giant hail and damaging gusts.

A level 2 surrounds the level 3 for large to very large hail, severe gusts and heavy to excessive rain. A tornado risk is present along the NW/N coastal fetch of the Adriatic Sea.

A level 1 surrounds the level 2 with similar hazards but lowered probabilities.

A rain-driven high-end level 1 was issued for parts of Czechia into Poland/Slovakia and far NE Germany for heavy rain with numerous excessive rain events not ruled out.

A level 1 was issued for the Caucasus and areas E mainly for some hail, gusts and rain.


SYNOPSIS

A complex upper air pattern exists for this forecast period. A barotropic ridge with negative PV anomalies along the 320K isentrope affects the W/CNTRL Mediterranean. This feature is accompanied by an impressive tropospheric thermal ridge.
Phasing of this ridge with another positive geopotential height anomaly over Norway/Sweden is underway and this scenario keeps any progression of Rossby wave activity blocked.

An upper low over N Germany, constantly gaining intensity during the past few NWP cycles, retrogrades along the S fringe of the Scandinavian anticyclone and remains connected to a quasi-stationary long-wave trough W of Iberia/the Bay of Biscay. A lowered thickness channel exists from Germany towards the English Channel.

An extensive but gradually filling trough still persists over far E/SE Europe into W Russia.

Once again synoptic-scale fronts won't affect this forecast, which is driven by a complex interaction of mesoscale dynamics (outflow boundaries, orography, BL moisture flux convergence) with an eastward sliding upper wave /IPV maximum, which moves from CNTRL France towards Austria.

DISCUSSION

Broadly speaking, we see an extensive overlap of strong shear (supergeostrophic enhancement and a tightened height gradient between the cut-off/short wave and the barotropic ridge to the S), rich BL moisture and enhanced mid-level lapse rates along the periphery of the extensive African EML. This results in numerous areas with organized DMC activity.

... France to Switzerland ...

A nebulous event is forecast as numerous waves of strong to severe thunderstorms are possible. Broadly speaking, we start beneath a strong and anticyclonic curved upper jet streak including a diffluent/slightly divergent upper flow regime. Another round of elevated WAA convection will be underway over W France before noon. This convection already poses an isolated large hail and heavy rain risk with MUCAPE in the 1000-1500 J/kg range.

From noon onwards, a mid-level low amplitude wave from the Bay of Biscay shifts towards CNTRL France until the evening hours. It's this time frame, when another transient BL vortex is forecast over CNTRL France, increasing BL lift on a regional scale by augmented moisture fux convergence signals. Finally, a transient coupled upper jet configuration increases upper divergence.

A bimodal event is forecast with one maximum of CI along the Massif Central E towards Switzerland. High based supercells with large to very large hail and severe/damaging gusts will be the main hazard beyond noon. Some local flash flooding is possible. This activity grows upscale into a progressive and severe MCS, which either turns into S Switzerland or SE France with large hail, severe gusts and heavy rain.
Switzerland has a favorable CAPE/shear space during the day, but degree of CI is a bit uncertain as subsidence along the periphery of a growing French cluster could hamper initiation. ID2-EPS LPI has no real minimum over Switzerland, so we go ahead and mention the chance for numerous supercells and/or clusters with all kind of severe. Nowcasting is needed for highlighting the corridor of most augmented severe.

A few organized thunderstorms are also possible from E France towards the Vosges area, although forecast hodographs reveal stronger mid-level backing, decreasing effective SRH a bit. Large hail and severe gusts are certainly possible however.

The other area of concern arises from WAA convection over NW France, which builds SE along the fringes of the E-ward moving and gradually filling surface low (respectively along an NW-SE aligned warm front, which runs from NW France into SW Germany). Hodograph signatures point to a few HP supercells with large hail, excessive rain and severe gust, which move from NW into CNTRL France during the afternoon into the evening hours.

... SW Germany to parts of Switzerland and Austria ...

The NW-SE aligned warm front edges into SW Germany and will be the focus for ongoing or very early CI on an isolated scale. Despite lingering subsidence from the synoptic-scale, the availabe thermally direct circulation along the warm front could support isolated morning convection, which will already be organized admits effective 15-20 m/s DLS. Large hail and isolated severe gusts will be the main risk with elevated morning convection. This activity however could turn more surface based until noon with large hail, severe gusts and heavy rain and a few severe hailstorms could enter W Austria from the NW. Damaging hail/gusts are possible.

Beyond noon, the troposphere recharges behind the initial convection and an impressive afternoon CAPE/shear space evolves. MUCAPE up to 2000 J/kg and long/straight hodographs (25 m/s DLS and 15 m/s 3 km shear) create a volatile background. The main uncertainty is if current NWP guidance takes the morning convection SE too fast. Lingering storms could hamper CAPE build-up. Also, the passing wave over Switzerland places SW Germany in a rather weak lift environment from the synoptic perspective.

The latest idea is that modest lift assists in scattered discrete supercell initiation during the afternoon onwards. Right moving cells will see ample of helical inflow in the lowest 3km, assisting in intense updrafts. Very large hail in excess of 5 cm is possible with deep updrafts and modest sub-freezing CAPE next to mentioned favorable kinematics. A mixed BL also assists in severe gusts and the combined effect could result in confined swaths with enhanced damage, which also includes the mountainous area of W Austria into far NE Switzerland. This risk lasts into the evening hours before a gradual weakening trend is forecast.

We pulled the level 2 quite far NW into the Vosges area to account for the aggressive ICON, which shows ample of CAPE/shear. This area is more uncertain and nowcasting trends will determine, if a downgrade could be needed.

... S Switzerland to N Italy and S Austria into Slovenia and Croatia...

Two waves of (extremely) severe thunderstorms are forecast.

The first round will be convection along the S Alps from N Italy and S Austria. Initiating cells will see roughly 1000 J/kg MUCAPE, strong shear and a mixed BL, so large hail and severe gusts will be the main hazard. Further W, towards S Switzerland, firing convection will already be placed in a 2000 J/kg CAPE environment and strong shear, so rapid supercell development is forecast with very large hail and damaging gusts.

Betimes, convection from N Italy moves off the orography and into an extreme CAPE/shear space with MUCAPE up to 3500 J/kg and 25 m/s DLS, so rapid intensification is forecast. Very large hail (probably in the 5-8 cm range) is possible next to heavy rain and damaging gusts. Despite increasing CIN after sunset, this activity continues well into the night. This is also true for Slovenia int Croatia, where less CAPE but favorable kinematics support long-lived supercells. Damaging hail and severe gusts are forecast next to heavy rain.

Finally the regions Lombardy, Emilia-Romagna and Piemonte have to be highlighted for an augmented evening/overnight risk of long-tracked severe supercells/bow echoes. As the synoptic-scale wave approaches from the W, the mentioned extreme CAPE/shear space favors swaths of damaging hail, gusts and excessive rain along the highlighted regions. This activity is persistently highlighted by long/intense UH tracks and LPI maxima, so given the augmented risk of giant hail/hurricane-forced gusts, a confined level 3 upgrade was performed. This event also affects the N Adriatic Sea with dangerous offshore conditions during the evening/night.

SE-ward moving mature supercells, which interact with the onshore moving sea breeze front from the N Adriatic Sea could also pose a tornado risk despite well mixed BL conditons.

... Parts of Czechia into E Saxony and Poland/Slovakia but also NE Germany ...

A lingering risk of slow moving clusters with locally excessive rain will be the main story from 06Z onwards and numerous 50-100 mm events in 3-6h are possible. This activity is bound to the near quasi-stationary upper low, which retrogrades late during the day. Anomalous TPWs up to 40 mm and a favorable environment for slow moving/back-building convection take this risk towards S/SE Poland and Slovakia during the day, either by the synoptic vortex or residual MCVs. During the night, this favorable fetch of training thunderstorm activity could also expand NW all the way into NE Germany.

Flash flooding is certainly possible on a regional scale and an extreme event cannot be ruled out.

... Other level 1 and ligtning areas ...

NE Spain into far S France will probably see another round of suppressed CI due to the stout cap. EPS/ENS signals for some precipitation increase a bit beyond noon and the layer above 650 hPa turns moist during the day, so some CI is possible along the orography of NE Spain. This idea is also supported by a passing weak IPV lobe around peak heating. Spotty large hail and severe gusts will be the main risk. Despite very reluctant deterministic runs, we issued a low confident level 1.

A few strong storms are possible over the Caucasus into Russia and a level 1 for isolated hail/gusts and heavy rain was added. Deeper into Russia, forecast profiles support slow moving convection with copious amounts of small hail and heavy rain on a local scale. This is not enough for upgrading.