Storm Forecast
Valid: Tue 03 Jun 2025 06:00 to Wed 04 Jun 2025 06:00 UTC
Issued: Mon 02 Jun 2025 19:55
Forecaster: TUSCHY
A level 2 was issued for parts of E/NE Spain into far SW France mainly for large to very large hail, severe gusts and heavy rain.
Numerous level 2 areas were issued across S-CNTRL France all the way into far NW Italy, over far NE Switzerland into S Germany and N Austria, another one over SE Austria into W Hungary and finally a small one over NE Italy mainly for large to very large hail, swaths of severe gusts and heavy rain. An isolated tornado event is possible.
A level 2 was issued across the N Ukraine and far S Belarus for large to very large hail, severe gusts and heavy rain. An isolated tornado event is possible.
A level 2 was issued for far E Slovakia into far SW Ukraine and far E Hungary mainly for large hail, severe wind gusts and heavy rain.
All level 2 areas are surrounded by a broad level 1 with similar hazards but lowered probabilities for all kind of severe.
A level 1 was issued for parts of the Atlas Mountains for large hail and severe donwbursts.
SYNOPSIS
A strengthening and blocking ridge becomes established over SE Europe, which faces a constantly deepening cyclonic gyre over far NW Europe into Iceland. Latest EZ-ENS data has a rather tightly clustered MSLP member cloud in the 970-975 hPa range for this vortex, which is rather low/impressive for this time of year. This vortex gets not only framed by the mentioned positive height anomalies over SE Europe but also by another area of positive anomalies over the far E-CNTRL (subtropical) NE Atlantic. This configuration results in an extensive belt of at least two anomalous strong upper jets, one exiting E towards NW Russia with another one approaching from the NE Atlantic.
Most of Europe resides in a cyclonic W/SW-erly mid/upper flow regime, which partially overlaps with an extensive CAPE plume admit constantly improving BL moisture along a zonally aligned synoptic-scale front (which runs from N Spain to S-CNTRL Germany and E towards the Ukraine). This front serves as main focus for DMC activity on a national scale.
DISCUSSION
... Spain ...
Most of Spain resides beneath an upper trough, which temporarily opens up into a wave before merging back into the polar front jet.
CNTRL parts of Spain see weak shear beneath the vortex and slow moving/clustering convection occurs in 500-1000 J/kg MUCAPE and less than 10 m/s DLS. Heavy rain/large amounts of small hail and a few strong downburst gust are forecast.
Kinematics improve steadily towards E/NE Spain, where MUCAPE pushes into the 1000-1500 J/kg range with DLS between 20-25 m/s and up to 15 m/s 0-3 km shear (peak overlap next to the coast). Numerous long-lived multicells and supercells with large hail, severe gusts and heavy rain are forecast. Splitting cells are anticipated as backed wind profiles cause rather straight/elongated hodographs. Destructive intereference of cells occurs, which lowers longevity of any cell but any longer-lived (semi-)discrete supercell could produce even an isolated very large hail event in excess of 5 cm in diameter. This activity weakens beyond sunset.
... S-CNTRL / E France, S Germany into Switzerland, Austria and N Italy ...
Sliding the boundary E towards France, we see a broad belt of 800-1500 J/kg MUCAPE overlapping with 15 m/s DLS and 0-3 km shear in the 10-15 m/s range. Weak ridging aloft keeps CI in check until noon/early afternoon before a passing weak wave and diabatic heating/the orography itself cause scattered CI. Most likely areas for CI reside along the Pyrenees N into SW France but also along the Massif Central E towards Switzerland and far NW Italy.
WAA along/S of the front enlarges hodographs, which show better LL curvature especially towards E-CNTRL France but also over far NW Italy (forced by the orography). CAPE/shear space supports numerous multicells and a few long-tracked supercells. Diffuse background forcing should assist in more discrete CI with a mix of classic to HP supercells as upper winds abate. Expect large to isolated very large hail, heavy rain and strong to severe gusts the main risk but modest 0-3 km CAPE, LCLs around 500-700 m and slightly enhanced LL shear along the front itself also indicate an isolated tornado risk, especially towards E-CNTRL France into far W Switzerland.
Towards NE Switzerland into Austria and far S Germany, CAPE shear space resembles the parameters further W, although CAPE remains a bit less bullish. ICON however increases 0-3 km shear into the 20 m/s range from Switzerland into S Germany, which would enlarge the lower parts of the hodograph, offering lots of strong SR inflow, with ICON pushing into the 30 kt 0-2 km SR inflow range. Lots of shear for sure for a mix of multicells, bowing segments and a few supercells with all kind of hazards possible including large hail, severe gusts and heavy rain but also an isolated tornado event. We added this area into a level 2 for the chance of a few long-trakced cells with all kind of hazards including hail larger 5 cm in diameter.
... SE Austria into Hungary ...
Another favorable area for organized multicells and a few supercells exists in the mentioned area although there could be an issue with increasing CIN as convection moves away from the orography. EZ remain more bullish with the cap, whereas ICON indicates only weak CIN. As convection taps into a plume of very unstable air into far W Hungary, upscale growth into a longer-lived bow echo is a possibility with up to 15 m/s 0-3 km shear forecast. The main hazard in this area of interest will be large hail, severe gusts and heavy rain. An isolated tornado event during the more (semi) discrete phase is possible. This is more a borderline level 2 event and depends on the final magnitude of the cap.
... NE Italy ...
Although CI could be an issue with weak background lift, we expect at least isolated thunderstorms to evolve in the level 2 area. This activity shifts into 1500 J/kg MUCAPE with 15 m/s DLS, which is enough for a few well organized multicells and isolated supercells with large hail and severe gusts next to heavy rain.
... Parts of E Slovakia to W/N Ukraine and far S Belarus ...
Yet another area along the front, which experiences plenty of CAPE for deep updrafts with MUCAPE pushing into the 1000-1500 J/kg range including local higher peaks. DLS increases up to 15 m/s next to the SE ward shifting cold front with similar peaks in the 0-3 km layer, so a mix of multicells/bowing segments and a few supercells is forecast with large hail (isolated very large hail not ruled out), severe downbursts and heavy rain on a local scale. Due to the high coverage of severe with a few extreme (hail/wind) events not ruled out, another level 2 upgrade was performed for N Ukraine into S Belarus. Betimes, a structuing LL depression, widespread CI and an improving outflow connection to the right entrance region of an upper jet streak over NW Russia could support upscale growth into a large cluster of storms, like an MCS and even further structuring into a long-lived MCV event is possible, which shifts into Russia during the overnight hours before starting a gradual weakening trend. A broad area of heavy rain could evolve along the N/NW fringe of the progressive surface low, which crosses the far N Ukraine E and places far SE Belarus in the highest risk for heavy rain on the broader scale.
E-Slovakia was also upgraded as a plume of 1000-1500 J/kg MUCAPE interacts with 15 m/s DLS. A passing wave adds enough background lift for scattered to widespread CI with a mix of multicells and a few supercells. Large hail, severe gusts and heavy rain become the main issue. This activity grows upscale into a SEward shifting cluster betimes.
... Poland into the Baltic States ...
Placed N of the surface front and affected by rather strong subsidence behind an eastward departing mid/upper wave, isolated to scattered CI is still anticipated beyond noon in a more or less uncapped airmass. 300-600 J/kg MUCAPE and strong DLS are enough for a few organized thunderstorms with rotating updrafts, which cause some hail, gusty winds and instances of heavy rain. An isolated tornado event cannot be ruled out especially from NE Poland into NW Belarus and SE Lithuania, where confidence for CI is a bit higher. We covered this area in a broad level 1.
... N Algeria ...
A few thunderstorms erupt along the orogaphy with lots of mid-level CAPE and adequate shear for a few rotating updrafts with large hail and severe downbursts.
