Storm Forecast
Valid: Fri 17 Jul 2026 06:00 to Sat 18 Jul 2026 06:00 UTC
Issued: Thu 16 Jul 2026 18:06
Forecaster: PUCIK
A level 2 was issued in a belt from E France through the Alpine range into SW Hungary mainly for large to very large hail and severe wind gusts.
A level 1 was issued from central France to Germany, Poland, Czechia, Slovakia, Denmark, N Austria and Hungary mainly for large hail, heavy rainfall and severe wind gusts.
A level 1 was issued from southern Norway into central Sweden mainly for heavy rainfall.
... NE France through Germany to Denmark, Czechia, S Sweden, W Poland and N Austria ...
Ahead of a weak frontal boundary, moist airmass with specific humidty around 12 g/kg will overlap with modest mid-tropospheric lapse rates of around 6.5 K/km. As a result, MLCAPE will reach 1000 to 2500 J/kg. Moderate vertical wind shear is forecast, reaching 10 to 15 m/s in the 0-6 km layer, locally perhaps slightly higher. Scattered storms will be initiated by the frontal boundary, leftover outflow boundaries/MCVs from early morning storms and orography. A mix of multicells, small linear segments and transient supercells is expected with various hazards. Large hail will be most likely in the early phases of the storm with threat more shifting towards wind and rain as storms grow upscale. Storms will spread east during the day and will persist overnight especially over Poland.
... SE France through Alps into SW Hungary ...
This will be the primary corridor of severe weather. Expect that some early morning storms will exist over the area and may influence the secondary development of storms in the early to late afternoon hours. Strong unidirectional shear of 20 to 30 m/s in the 0-6 km bulk shear is forecast, supportive of splitting supercells. Supercells are forecast also by the high-res models and with MLCAPE of around 1000 J/kg, they will be capable of large to isolated very large hail and severe wind gusts. Given fast storm motion, long hailswaths are possible. A development of linear segment is possible especially towards E Austria and W Hungary, where the threat could shift more towards damaging wind gust should this happen. In this region, expect storms developing over the Alps and spreading towards N Slovenia, W Hungary and perhaps NW Croatia. How far south/southeast will the storm activity spread is questionable. Except for the western Hungarian plains, there is a high uncertainty if some right-moving supercells will make it over Piemonte, Lombardia or FVG plains. Some members of the high-res ensembles point at this possibility and it should be taken seriously as storms will tap into much higher CAPE environment. However, the presence of a significant dry layer in the mid-troposphere will allow only the truly powerful storms to "pass".
.. S Norway to central Sweden ...
A slowly moving, but pronounced cold front will provide a widespread lift for airmass characterized by MLCAPE between 500 and 1500 J/kg. Majority of storms will form on the cool side of the boundary and will be elevated. Slow motion of the boundary toward the south, while storm motion will be to the north, points at a risk of cell training and excessive rainfall. Marginally large hail may also occur with stronger updrafts, especially those that develop closer to the boundary in CAPE richer airmass.
