Storm Forecast
Valid: Tue 21 Jul 2026 06:00 to Wed 22 Jul 2026 06:00 UTC
Issued: Mon 20 Jul 2026 21:34
Forecaster: PUCIK
A level 3 was issued from Italy to S Croatia, S Bosnia, Montenegro and Kosovo mainly for very large hail, destructive wind gusts and to the lesser degree for tornadoes.
A level 2 was issued from Italy to Romania and Bulgaria mainly for large to very large hail and severe wind gusts.
A level 1 surrounds level 2 for the same threats but with lower coverage.
A level 1 was issued for Pyrenees mainly for large hail and severe wind gusts.
A level 1 was issued for Baltics mainly for heavy rainfall.
DISCUSSION
!!! This situation will likely result in a major severe weather outbreak from Italy towards southeastern Europe. Fast-moving and long-lived supercells and bow-echoes with long swaths of (extremely) severe weather are forecast !!!
After days of zonal flow without any major disturbances across the forecast area, a trough at mid to upper troposphere will approach from northwest. This will lead to:
1. Further intensification of vertical wind shear, especially above 1 km
2. Synoptic-scale lift overspreading the area and eroding the CIN and moistening the mid-troposphere
3. Frontal zone shifting south throughout the afternoon and evening hours with cooler and drier air following behind.
Expectation is that both the coverage of storms and also the intensity will ramp up compared to the previous day(s) from central Italy into Bulgaria and Romania. Especially over Italy, southern Bosnia and Montenegro, an extremely impressive CAPE-shear overlap is forecast with 1500 to 3000 J/kg of MLCAPE, 0-6 km bulk shear of 25 to 35 m/s and 0-3 km shear of around 20 m/s.
... Italy ...
From the thermodynamic perspective, Apennines and adjacent eastern lowlands in Italy will be the area with the highest risk of giant hail, given the largest values of buoyancy above -10 deg C isotherm. Some morning storms will be possible, especially in the northwestern fringe of the Lvl 2 and these may dictate exactly where and when will be the start of the most intense starts. Expect initiation of supercells over Apennines and the Alps, spreading towards the lowlands and then over the Adriatic Sea. ICON-D2 EPS shows high likelihood of supercells combined with very high values of updraft helicities with the storms initiating over the Apennines. Destructive hail and wind gusts are expected, sometimes in combination with a possible upscale growth as storms interact together. Straight hodographs point to the possibility of storm splits, which upon the collision of right- and left-movers can speed up the upscale growth into a bow-echo that may race through the Adriatic eastwards. While tornadoes will not be the main hazard, a strong tornado is not ruled out given the impressive CAPE-shear parameter space, combined with some local areas of 0-1 km bulk shear of 10 m/s and 0-1 km SRH of 100 m2/s2. Storms will spread south during the day with the highest threat between 12 and 21 UTC.
... Croatia, Bosnia, S Serbia, Montenegro, Albania ...
This region will have similarly strong deep-layer shear compared to Italy, though MLCAPE will be slightly lower, mostly in the range of 1000 to 2000 J/kg. Still, environment will be supportive of long-lived supercells and bow-echoes capable of very large hail and destructive wind gusts. Isolated spots of 0-1 km SRH around 100 m2/s2 also point to the possibility of a tornado with supercells. Storms will either: initiate directly over local orography, around the early afternoon hours and travel SE in form of isolated to scattered supercells. And/or: arrive from the Adriatic Sea in form of a long-lived supercells and bow-echoes that initiated over Italy. It is quite possible that a bow-echo capable of hurricane force wind gusts arrives from the Adriatic and continues inland. This scenario is especially likely should such system travel along the S-ward moving frontal boundary across the Adriatic, providing additional mesoscale lift. In any case, numerous rounds of (extremely) severe storms are possible in this region with activity persisting into late evening and night hours.
... Bulgaria and Romania ...
Isolated supercells are forecast in the afternoon hours with initiation tied to the local orography and lowlands staying mostly void of storms. Given substantial buoyancy above -10 deg C isotherm, supercells may be capable of very large hail. Besides that, expect isolated severe wind gusts in downbursts. Further increase in storm coverage is forecast in the late afternoon to evening with storms arriving from west and an approach of the frontal zone from north. A long-lived convective system may sweep across parts of the countries with severe wind gusts and large hail with storms exiting over the Black Sea towards the late night hours.
... Pyrenees ...
Isolated storms may form in an environment of strong shear and produce local downburst or large hail. Storm initiation is highly uncertain, but any sustained storm will benefit from favorable for severe storms.
... Baltics ...
In moist environment, skinny CAPE profiles, low LCLs and basically 0 mean wind, quasistationary showers and weak storms may produce locally high rainfall accumulations.
