Storm Forecast
Valid: Sun 28 Jun 2026 06:00 to Mon 29 Jun 2026 06:00 UTC
Issued: Sat 27 Jun 2026 16:07
Forecaster: TUSCHY

A level 2 was issued from NE Spain to France to Germany into S Sweden and NW Poland (including adjacent areas) mainly for large to very large hail, severe to damaging gusts and heavy to excessive rain.

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

A level 1 was issued for parts of CNTRL/S Italy mainly for excessive rain, large hail and gusts.

A level 1 was issued for parts of SW Russia mainly for hail, gusts and heavy rain.

SYNOPSIS

Extensive ridging persists over most of Europe with troughs confined to far NW and far E Europe but also to N Africa. A mobile low amplitude wave crosses Spain NE into S France during the day.

The western part of the level 2 gets framed by a gradually eastbound moving cold front. The main foci for CI however will be prefrontal outflow/mesocale convergence zones and surface pressure troughs with augmented moisture flux convergence but also passing/weak short waves.

DISCUSSION

... NE Spain, Parts of France, Belgium, Luxembourg to Germany into NW Poland and S-Sweden ...

A plume of extensive moisture advects N and features unseasonable high BL moisture content at least on a regional scale. This moisture input is driven partially by the intrusion of a subtropical airmass, but also by trajectories rooting into the NW Mediterranean, which experiences a severe marine heat wave with SST anomalies in the 4-7K range!
This moisture partially intersects a plume with steepened mid-level lapse rate, which is not a real EML but more a self-induced lapse rate increase by persistent subsidence and extreme positive temperature anomalies within the lower troposphere. The net result is an extensive MUCAPE plume of 1000 to regionally in excess of 3000 J/kg within the extensive area of interest.

Kinematics are mostly in the borderline range for organized DMC activity but with a regional increase into the 15-20 m/s range for 6 km bulk shear, while 3km shear magnitude resides in the 10-15 m/s range. Of note is the magnitude of DCAPE, which is in the 800-1500 J/kg range for most of the highlighted area. Hence, storm-intern dynamics will probably offset modest kinematics on the broader scale.

Main issue will be near absent synoptic-scale forcing as NWP guidance only highlights the passage of very weak IPV maxima. Short-wave activity in NWP guidance seems to be (at least partially) amplified by convective activity and hence not really reliable for CI forecast. However there are weak signals of low/mid-level frontogenesis, which could act to increase CI on a regional scale. Outflow boundaries and orography will be more foci to look for anticipated CI. In addition, a structuring 110 kt upper jet becomes more compact during the forecast and attendant divergent right entrance roots deeper into the extensive warm sector over CNTRL Europe (especially towards the night).

We start with an ongoing and gradually weakening MCS event over S Sweden into far NE Germany, which is accompanied by severe gusts and some hail next to heavy rain. Dependant on its timing, a diurnal destabilization trend downstream of the MCS could increase its strength again and attendant gust risk. Another round of strong to severe thunderstorms is possible over S Sweden during the afternoon with large hail, severe gusts and heavy rain. Recovering trend of the BL airmass needs to be monitored, dependant on how fast the MCS clears the area E.

Attendant outflow probably drives deep into NE Germany/NW Poland where it gradually dissolves. Intense differental heating establishes a zonal thermal gradient, which itself could be the focus for CI later the day but also residual BL convergence zones as the outflow breaks apart. Extreme heating erodes lingering CIN during the afternoon with isolated/scattered CI of high-based convection (LCL aoa 3km AGL). Dependant on the storm coverage, a growing cold pool could push an MCS into NW Poland. Very efficient downdrafts can produce severe to damaging gusts with isolated large hail. NWP weakens any potential MCS over NW Poland rather fast but would not be surprised about a longer-lived MCS event, riding the zonal thermal gradient E and hence deeper into N/CNTRL Poland (despite moving deeper beneath the ridge). Any storm, latching along the thermal boundary could produce an isolated tornado event, although even this environment will be only marginal favorable to say at least.

Other then that, the expected evolution of thunderstorms becomes too diffuse for diving deeper into details.

In general, NWP gudiance seems to react to the passage of a weak wave with scattered CI over E-CNTRL France into NW and CNTRL Germany (12z onwards). During the later forecast period (late afternoon into the evening hours) another increase of CI proabbilities is noted over the Massif Central but also along the Pyrenees.

Each activity will start with a mix of multicells and semi-discrete supercells and this activity is accompanied by large hail (numerous hail events in excess of 5 cm possible), strong to severe gusts and heavy rain. Betimes, numerous long-tracked severe MCS events could affect parts of the extensive level 2 area, as cold pools mature betimes. Swaths of severe/damaging gusts are possible with a mix of large hail and heavy to locally extreme rainfall amounts (as TPWs hover in the 35-45 mm range).
If we get a structuring MCS into CNTRL Germany going, the thermodynamic and kinematic background downstream could indeed support a severe NE ward racing MCS event with embedded RIJ/bow events and some NPW data is even hinting at a potential derecho event.
Another area of concern for swaths of damaging gusts exists for the convection over the Massif Central racing NE into E-CTNRL France during the evening onwards.
Finally NE Spain and far SW France could be in for more/severe MCS activity with damaging gusts, large hail and excessive rain as the mobile trough approaches from the W.

Nowcast trends need to be monitored closely within the extensive level 2 area for changes f.ex. by convection from the previous night.

... Alps into N Italy...

Slow moving and clustering convection poses a risk for locally excessive rain, hail and strong gusts. High/deep moisture content could support a few extreme rainfall events with damaging flash flooding. During the evening, convection moves S into N Italy, where stronger cap weakens convection betimes.

...CNTRL/S Italy ...

Despite ridging aloft, ongoing marine heat wave in combination with onshore emoving sea breeze fronts assist in extreme MUCAPE build-up up to 4000 J/kg on a local scale. Any updrafts, which break the cap could be accompanied by extreme rainfall, large hail and gusts.

... Far SW Russia ...

Scattered organized storms with hail gusts and heavy rain are forecast.