Valid: Sun 05 Jul 2015 13:00 to Sun 05 Jul 2015 16:00 UTC
Issued: Sun 05 Jul 2015 13:52
Across the area, mid-level flow is increasing from the west as the trough approaches. A well-defined surface cold front was located along a line from a line from Utrecht to Brussels to Bourges at 12 UTC.
Ahead of the front, prefontal convection has induced an outflow boundary stretching from northern Belgium, to near Aachen to Kassel. Along this line, surface convergence is occurring and storms are starting to develop near this zone.
The Essen 12 UTC sounding indicated ample deep-layer shear, but also an air-mass that requires quite some recovery before surface-based convection can occur. This may be different a bit further south near the outflow-induced convergence across the Rhineland. The Essen sounding also showed that mid-level flow has strengthened to 20-25 m/s.
It appears likely that the storms that are now initating over the Rhineland will develop into a number of supercells capable of producing large hail and severe wind gusts.
it is very difficult to assess whether surface-based convection will also be able to develop within the cold pool north of the boundary. If so, a few tornadoes may also develop in the next hours, most likely just north of the outflow boundary - which will likely move northward over time. Here, low level shear should be maximized due to the easterly surface winds, and low-level shear should exceed 10 m/s.