Storm Forecast
Valid: Mon 13 Jul 2026 06:00 to Tue 14 Jul 2026 06:00 UTC
Issued: Sun 12 Jul 2026 09:30
Forecaster: TUSCHY
A level 1 was issued for the S Alps mainly for large to isolated very large hail, severe gusts and heavy rain.
A level 1 was issued for parts of NE Spain into SW France mainly for large hail (an isolated very large hail event is not ruled out) and severe gusts.
A level 1 was issued for parts of CNTRL France mainly for large hail and severe gusts.
A level 1 was issued for NW Germany into Denmark for isolated heavy rain. A low-end tornado risk exists for far N Germany into Denmark.
SYNOPSIS
A barotropic ridge, filled with tropical air (negative PV along the 320 K isentrope) starts to get in phase with a blocking anticyclone over NW Europe. Both features suppress any east motion of Rossby waves and even some retrogression is noted in latest Hovmoeller diagram.
This extensive ridge gets framed by a stationary trough W of the Bay of Biscay and a complex longwave trough over E Europe, which has numerous separate axes. A weakness within that ridge exists over Germany W towards the Bay of Biscay and a structuring zonally aligned trough axis evolves from CNTRL into W Europe.
Despite some weak/transient vortices within the lower troposphere (e.g. the Netherlands and CNTRL France), the MSLP gradient remains relaxed with no major frontal intrusion forecast.
DISCUSSION
... S Alps ...
Good diabatic heating and a diurnal onset of the Alpine pumping should induce enhanced CI probabilities along the S Alps. From noon onwards, expect numerous thunderstorms to initiate within a favorable CAPE shear space, as MUCAPE resides in the 2000 J/kg periphery with DLS in the 15-20 m/s range. In addition, a regionally augmented 0-3 km shear vector is noted, which results in elongated and straight hodograph signatures. Splitting cells are forecast with right movers drifting off the orography betimes and into a stronger capping background, which induces a gradual weakening trend betimes.
Overall there is a risk of numerous SE-ward moving severe hailstorms with large to very large hail (a few events with hail in excess of 5 cm), severe gusts and heavy rain. We thought about upgrading, but the confined CAPE swath and increasing capping issues beyond sunset/off the orography kept this in an high-end level 1.
... NW Germany to Denmark ...
A rather uncertain rain-driven level 1 was added. Dependant on the final track of a small-scale upper low and its low-tropospheric imprint, we could see a few afternoon thunderstorms over NW Germany. ICON is very reluctant regarding CI but right now this model remains an outlier regarding the handling of the upper vortex' path. But even ID2-EPS has some better LPI signals over NW Germany beyond noon.
A moist background with PWs in the 25-30 mm range and near zero storm motion thanks to contrary winds within the troposphere point to quasi-stationary convection with a heavy rain and local hail risk (the latter risk due to MUCAPE up to 1500 J/kg). Nowcast is needed regarding increased or lowered CI chances during the following NWP cycles.
Confidence in CI increases towards Denmark with slow moving convection posing an heavy rain risk on the local scale. In addition (but dependant on the vortex' path), augmented CAPE3 could cause a non-mesocyclonic tornado event from Denmark into far N Germany.
... Spain to France ...
A volatile environment exists with MUCAPE in the 2000-3000 J/kg range and DLS in excess of 15 m/s for most places. Capping however remains sturdy and most deterministic runs show little CI. In addition, drying in the 600 hPa layer could hamper growing updrafts and lower ECAPE magnitude.
However we stick with better signals in some EPS maxima of QPF as most of NE Spain and France reside beneath improving upper divergence, as a few weak waves shift NE/E during the day.
Hence we expect a few thunderstorms over NE Spain, erupting along the orography during the late afternoon onwards with minimal capping. Any more robust updraft could take profit of more than 2000 J/kg MUCAPE and 15-20 m/s DLS, so large hail and severe gusts would be the main issue. The same for convection over SW France, which starts along the orography (Pyrenees) and weakens betimes due to a strengthening cap with similar hazards. A level 1 was added.
Another level 1 was added for parts of CNTRL France. In response to improving BL moisture flux convergence and mixing ratios from the W, we could see nearly uncapped 1500-2000 J/kg MUCAPE around peak heating. DLS in the 15 m/s range is enough for a few organized multicells and large hail/severe gusts (deep BL mixing) are forecast. This convection spreads east and turns more elevated betimes with a decreasing severe risk.
... Baltic States to Belarus/E Poland ...
Another day with scattered slow moving thunderstorms is forecast. The airmass is worked over with weakened mid-level lapse rates. Rich BL moisture however still assists in MUCAPE up to 1500 J/kg. Initiating cells pose a local hail and gust risk. The main hazard however will be heavy rain on the local scale. Missing foci for any enhanced severe risk preclude a level 1 for now.
In addition a growing nocturnal cluster is possible over E Poland in response to the deforming upper low from the NW with improving upper divergence. Heavy rain will be the main hazard.
