Storm Forecast
Valid: Fri 05 Aug 2011 06:00 to Sat 06 Aug 2011 06:00 UTC
Issued: Thu 04 Aug 2011 21:50
Forecaster: KOROSEC

A level 1 was issued for NE Iberia into central France mainly for large hail, excessive convective rainfall and strong winds.

A level 1 was issued for SW Balkan peninsula mainly for excessive convective rainfall and some strong wind gusts.

SYNOPSIS

A deep trough/low west of UK will be the focus for today's activity. An associated mid-level jet advects moisture well to the north across central Europe. A weak short-wave trough is still in place over the Balkans, affecting the SW part of Peninsula. At surface, a cold front moves across the W-CNTRL Europe and rounds towards NW across SW Scandinavia around the SFC low over North sea.

DISCUSSION

... SW Balkan peninsula ...

Another day of rather robust and widespread convective activity for the Balkans. While shear remains low, high PBL moisture and warm/hot airmass provides moderate instability. Once the weak capping in eroded, storms will initiate by early afternoon hours. Multicells will be the primary mode. Given then expected slow storm motion vectors, the main threat will be the flash flooding and locally some strong winds. Some marginal hail will also be possible, but less likely than other threats. Storms will diminish soon after sunset when instability rapidly vanishes.

... NE Iberia into central France ...

A SFC cold front and an upper level disturbance arrives into western Europe towards the afternoon hours, providing some QG forcing. Warm and unstable airmass remain in place ahead of it. Storms should first initiate along the convergence zones over the complex terrain of NE Iberia and central France, then also along the frontal boundary. Combined with moderate instability and at least around 10-15 m/s of deep layer shear, organized severe storms will be possible. Those could locally bring some large hail and strong winds. Given the high PWAT values, local flash floods are possible as well.

Elswhere, marginal instability and low shear precludes any severe storms to occur, so mostly daytime driven activity is expected. Some overlaping seem likely to occur along the lifting front into SW Scandinavia, but too low probabilities to warrant a threat level 1.