The long-lasting heat dome and heatwave across a large part of Europe is, at least temporarily, collapsing and will be replaced with much colder air mass. Significant weather will likely develop across central Europe, accompanied by severe thunderstorms, hail, flooding, and damaging winds.
A dramatic weather change comes after a long period of unusually hot weather across much of continental Europe in recent weeks. As we reported, many countries and hundreds of weather stations have shattered their highest temperature records for June, some even July records. The heatwave was historic.
The heat dome, which has trapped an extremely warm air mass underneath, is finally losing its breath and is expected to collapse as we head into the weekend. Triggered by a building blocking High over the North Atlantic, a cold wave emerges from the north towards central Europe, with significantly colder air masses forecast early next week.
This will create a strong temperature and pressure contrast between the cold wave from the north and a decaying intense heatwave in the south. With amplified upper-level winds (jet stream) supporting intense lifting, widespread severe weather development is likely from Saturday through Tuesday.
Below is the video animation of the weather pattern change and much-needed refreshment and rainfall for some parts of the European continent. Significant to extreme drought conditions have been observed in many countries, followed by much below-normal precipitation in recent weeks and months. It is time for a short break.
Let’s dig into the pattern evolution over the weekend that will lead to severe weather and flooding potential early next week.
Sharp pattern change takes place, leading to a heat dome to collapse, and a cold wave blast follows
The weather pattern change will be dramatic over the weekend into early next week, thanks to a strong upper-level ridge strengthening over the North Atlantic. This causes a deep cold wave from the north to dig far south into central Europe and towards the Mediterranean after Sunday.
This is typical when an intense blocking High over continental Europe collapses and is disturbed, replaced by an upper trough or low. When this occurs, severe weather followed by cold refreshment is expected.
The surface pressure chart is even clearer regarding the emerging dipole weather pattern; on Monday, we can see a strong Azores high-pressure system with an extensive low-pressure system over northern and central Europe.
Since the air mass in the Northern Hemisphere travels counterclockwise around the Low and clockwise around the High, we can see that the air flow will be from the north towards the south between the two large-scale weather systems.
The air mass behind the core of the upper wave/low will be significantly lower than we have been experiencing in the recent weeks, around 5 to 8 °C below normal at the 850 mbar geopotential height (approximately 1200m above sea level). This is quite anomalous and a significant change. If we remember, we had an air mass around 12-15 °C that was too warm just recently.
As we can see, the remnants of the heatwave will travel far east into eastern Europe and the Black Sea region mid-next week.
The temperature change and contrast between the current exceptionally high temperatures and those forecast for Monday and Tuesday next week will be even more dramatic.
While temperatures on Thursday and Friday this week were 10-12 °C above the average, a noticeable difference is seen if we compare them with temperatures the following Tuesday. Those will be 6-10 °C below normal at the surface levels. So, there is nearly a 20 °C change from the current ones.
Once the upper cold wave begins shifting east around Wednesday, temperatures will start climbing back into the upper 20s to 30s, also thanks to intense Sun heating in early-mid July and a return of the warm plume from southwestern Europe.
Record-breaking marine heatwave to fuel widespread severe weather beneath an intense jet stream
The ongoing record-breaking marine heatwave across the Mediterranean is a vast energy reservoir for thunderstorms. High water temperatures mean the moisture is much higher than usual, and warm air temperatures significantly increase dewpoints.
You can read more about the ongoing historic marine heatwave here: Mediterranean Marine Heatwave brings water temperatures to record levels.
With 20-30 °C sea waters across western and north-central Mediterranean, dewpoints will be around mid-20s across North Italy.
This directly translates into high energy fuel for thunderstorms, pushing Convectively Available Potential Energy (CAPE) into the 2000-3000 J/kg range. This is high to extreme instability.
Placed underneath an intense jet stream aloft, associated with the deep cold wave, intense upper-level winds will support widespread lift and forcing for thunderstorm initiation.
The following chart represents 200 mbar winds, with a textbook jet stream rounding the base of the cold wave/trough. The most favorable period for widespread thunderstorm activity from Sunday through Tuesday is marked with a red box.
Therefore, a combination of high instability, coupled with strong winds aloft, will provide conditions to support severe thunderstorms. Those will be capable of producing all weather hazards, including large to very large (giant) hail, damaging winds, torrential rainfall, and tornadoes.
Strong wind shear on Sunday will support violent thunderstorm activity from Switzerland to Austria and northern Italy. In contrast, from Monday to Tuesday, the most significant forcing will support widespread storms across Italy, Slovenia, and northern Croatia.
A multi-day severe weather event will also contribute to high rainfall sums across central Europe, precisely around the Alps from Switzerland and Austria to northern Italy, Slovenia, and northern Croatia.
Locally, rainfall amounts are likely to reach 100 to even 200 mm in places, mainly if severe thunderstorm clusters with trailing cells occur. Therefore, the area also supports torrential rainfall, flash floods, and mudslides risk.
However, the amounts of rainfall will vary a lot since severe storms will be isolated despite the widespread thunderstorm activity.
Rising potential for another significant heatwave through mid-July 2025
The upcoming weather change is forecast to gradually vanish by mid-next week, and then global models indicate a return of significant heat back into continental Europe.
Although this forecast is still around 10 days in advance, the general trends hint at the new heat dome and blocking High forming after July 10th.
This would push temperatures back into the mid-30s to 40s in many areas, hence the anomaly charts hinting at a 10+ degrees Celsius warmer-than-normal air mass into mid-July.
It is still too far in advance to determine how intense and which regions will be worst hit, but it is worth monitoring the trends developing on both the GFS and the ECMWF weather models.
Evapotranspiration would be intense since such an intense heatwave would come after significant rainfall across central Europe. Thus, there would be much higher moisture and temperature dewpoints until the air mass dries out after a few days.
We will continue to monitor the evolution of the weather pattern and Mediterranean marine conditions in the coming weeks and update the forecasts accordingly. Stay tuned.
WeatherBell, Windy, Wxcharts, and ClimateBook provided images for use in this article.
