Forecast Update
Valid: Fri 03 Jul 2009 11:00 to Sat 04 Jul 2009 06:00 UTC
Issued: Fri 03 Jul 2009 11:19
Forecaster: TUSCHY

A level 2 was issued for the Pyrenees and surrounding areas mainly for large hail.

A level 1 was issued for extreme E-France, E-UK, Belgium, Luxembourg and W-/S-Germany mainly for excessive rainfall and large hail

A level 1 was issued for parts of the Czech Republic and N-Austria mainly for excessive rainfall.

A level 1 was issued for parts of Italy mainly for large hail and excessive rainfall.

A level 1 was issued for parts of Sweden mainly for large hail and strong to severe wind gusts.


SYNOPSIS

Please refer to the main outlook.

DISCUSSION

... Belgium, the Netherlands, Luxembourg, W-/S-Germany ...

The level-1 is scaled up, now including also W-/S-Germany and all of the Netherlands. 00Z sounding of Stuttgart already sketched the environment very well with a tongue of somewhat steeper lapse rates over the level-1 area. Although lapse rates start to weaken over S-Germany during the day, they remain ath the current magnitude over W-Germany , Belgium, Luxembourg and the Netherlands. Coupled with a very warm/moist boundary layer with surface dewpoints in the upper tens, lower twenties, abundant CAPE release is forecast. 1000 J/kg MLCAPE over S-Germany increases to probably 1500J/kg over the Netherlands and parts of Belgium.

Shear is very weak, what is reflected in latest VWPs. Also HIVIS images reveal quite symmetric anvil appearance. Clustering is already on its way over W-/S-Germany and today, some of those clusters could become better organized given degree of instability and cold pool strength. There is a high risk for flash flooding with this activity due to the slow storm motion and hight PWAT values. Next to that, large hail can't be ruled out despite weak shear, but hail cycling in feeder cells could offset that negative effect. Confidence increased regarding hail risk due to numerous robust updraft cores, represented in radar loops. In addition, persistent signals of 200J/kg LL CAPE in the level-1 area continue to indicate the risk for isolated tornadoes.

Thunderstorms keep going well into the night (probably all night long along eastward shifting convergence zone) with torrentail rain/isolated large hail being the main risk.

... Other changes ...

The thunderstorm/level area over Sweden was expanded to the SE due to the overall agreement in the evolution of a thunderstorm cluster, which ought to travel further to the south than anticipated.

The level-1 over the Pyrenees was upgraded as degree of thunderstorm coverage looks sufficient for more scattered initiation. Large hail and even an isolated extremely large hail event are possible.