Storm Forecast
Valid: Sun 03 Apr 2011 06:00 to Mon 04 Apr 2011 06:00 UTC
Issued: Sat 02 Apr 2011 21:42
Forecaster: DAHL

A level 1 threat was issued across central France and north Spain mainly for marginally severe hail and marginally severe straight-line wind gusts.

... SYNOPSIS ...

A deep long-wave upper trough is present over the eastern Atlantic and western Europe. This feature will slowly close off into a cut-off cyclone on Sunday, resulting in an eastward leap of the remaining northern portions of the trough. The low-level baroclinic zone tied to this trough will stretch from western Iberia northward nearly along the continental-European west coast into Scandinavia. The air mass east of this baroclinic zone is weakly unstable and will be the focus for scattered thunderstorms on Sunday.

... DISCUSSION ...

... eastern Iberia ... France ... Germany ...

It seems that a narrow plume of weak instability may materialize directly ahead of and along the surface cold front. Deep-layer and low-level shear will be minimal along most portions of the front, except over France and Spain, where 20 to 25 m/s DLS are expected.

Instability should be strongest over France (albeit still weak, probably less than a few 100 J/kg), decreasing further to the northeast into Germany.

It seems that scattered thunderstorms will form during and after peak-heating hours, aided by DCVA-related ascent. Over France, there exists a potential for line segments and/or mesocyclones, capable of marginally severe hail/winds. Shear and instability, as well as coverage may be somewhat less over eastern Iberia, but an isolated severe thunderstorm still seems possible.

Farther east ... it seems that isolated showers, capable of sporadic lightning, might form well ahead of the cold front over the mountainous regions of the Czech Republic, Slovakia, Austria, and Hungary. It currently seems that the overall lightning probabilities will be too low to highlight these areas.