Storm Forecast
Valid: Tue 17 Apr 2007 06:00 to Wed 18 Apr 2007 06:00 UTC
Issued: Tue 17 Apr 2007 04:03
Forecaster: VAN DER VELDE

SYNOPSIS

Unstable airmass at the eastern flank of a blocking Atlantic high pressure area will yield a number of thunderstorms mainly over northern Spain and southern France. Farther north the air seems to dry. CAPE values have decreased a bit compared to previous days, in GFS and real soundings, with shear becoming weaker. Storms may still cluster and may produce strong gusts and some hail, but the chance seems not as high anymore and will leave away a level 1.
A dynamically weak cold front pushes into warm air over Germany, Czech Republic, Poland and the Baltics, but the question is whether instability is good enough by early evening to trigger some thunderstorms with also some orographic lift... 00Z Bergen (DE) has some hints but isn't there yet. Forecast tops not as cold as in France.
A trough enters southern Scandinavia and may cause isolated thunder.
A trough over southern Italy is likely to cause widespread thunderstorms with some chance of marginally large hail where moderate shear may just interact with storms.

The level 1 over Morocco highlights an area of moderate deep layer shear (15-20 m/s) and more than 200 m2/s2 SREH at the north coast. This can produce large hail and severe gusts, but it is not certain if convection in the shear area will not be capped or elevated too much (not great 0-3 km CAPE, Casablanca 00Z dry..., MU parcel better). Most CAPE is produced by GFS in the center of the upper low, while more lift and shear is present eastward with less precip signals... recommend watching developments though.