Storm Forecast
Valid: Sat 07 Jul 2007 06:00 to Sun 08 Jul 2007 06:00 UTC
Issued: Fri 06 Jul 2007 23:51
Forecaster: DAHL

SYNOPSIS

Ample upper westerly flow exists over Europe, with an Atlantic upper trough slowly digging towards Europe during the period. Downstream ... an upper trough is present over eastern Europe and extreme western Russia. This upper system is accompanied by quite a strong surface low which maintains a strong westerly low-level flow over central Europe. Quiescent large-scale surface conditions prevail otherwise. The main frontal boundary is aligned parallel to the upper frontal zone, stretching from the N Bay of Biscay eastward across France and southern Germany towards SE Europe on Saturday afternoon per model guidance.

DISCUSSION

... Ukraine ...

It seems that strong DCVA-forced ascent will overspread the polar air mass over the Ukraine, which should become weakly unstable during the day. Strong shear profiles, especially at low levels, are expected. While this is supportive of low-level rotation of the thunderstorm cells, the LCL heights seem to be somewhat high, so the tornado threat may not be too high. However, wind gusts and hail, both reaching severe limits may locally occur.

... Spain ... S France ... N Italy ... Alpine Region ...

It seems that weak CAPE will evolve in the air mass across France and the N Mediterranean/N Italy. Current model guidance suggests that convective development will be very isolated however, and given minimal shear over these regions, severe threat should be accordingly small. Convection over the N Mediterranean region should reach peak activity in the late afternoon hours, while onsetting LL warm advection over W Europe may lead to an increase of convection over France and parts of Spain during the night/early Sunday morning.

... S Finland ... NW Russia ...

Thunderstorms are also likely over NE Europe and W Russia amidst plume of wrap-around moisture, associated with the NE European low-pressure system. Available numerical fields suggest that this activity will exist just outside the favorably sheared regions, so that the severe threat should be minimal on Saturday.

... N Germany ...

Comparatively shallow, and possibly weakly electrified convection should develop over N Germany with diurnal heating. Strong LLS will be in place, and chance for isolated/brief funnel clouds and tornadoes exists. Threat seems to be too low for a categorical risk, however.