Storm Forecast
Valid: Sat 05 Jan 2008 06:00 to Sun 06 Jan 2008 06:00 UTC
Issued: Fri 04 Jan 2008 19:43
Forecaster: DAHL

SYNOPSIS

Rapid transition to quite a progressive upper flow pattern is in progress ... at least over western and central Europe, as sturdy high pressure ridge persists across E Europe and Russia. Noteworthy is the strength of the upper frontal zone over the E Atlantic, suggesting some potential for rapid cyclogenesis along this frontal zone. However, for Saturday the past model simulations appear to be quite coherent in simulating merely a comparatively weak frontal wave at the nose of a 90 m/s Atlantic jet streak, affecting France on Saturday afternoon/evening. A large-scale SFC low-pressure complex is covering the NE Atlantic, with frontal waves moving along its S periphery. High pressure persists over E Europe and Russia.

DISCUSSION

... N Benelux ... N Germany ...

It seems that a tongue of weakly unstable polar air will be present underneath the lead vort max, which will be located over Benelux/W France by the beginning of the period. A couple of comparatively shallow thunderstorms may develop, bearing some threat for small mesocyclones, capable of spawning a brief tornado or two, given about 10 m/s LLS. Deepest convection should occur over Benelux and N Germany. Threat does not seem to be too robust, given only moderately strong LLS and rather weak DLS. It thus seems that the threat is too low for a categorical risk.

... W France to SW Germany ...

Some convective potential will also exist with the frontal wave that crosses France in the afternoon and evening hours, eventually moving into S Germany towards Sunday morning. At the moment it does not seem that the situation will become baroclinically unstable, so the degree of large- and mesoscale forcing for ascent will likely be limited somewhat. This is also reflected in the comparatively weak thermal structure of the system at low levels. At this time, it thus seems unlikely that a line of forced convection will appear along and/or ahead of the cold front belonging to the frontal wave. If convection did occur, threat for severe wind gusts and for isolated tornadoes would exist. Potential is too low to warrant a level-one threat area, although the probability for severe weather is slightly enhanced over this region.