Storm Forecast
Valid: Sat 23 Apr 2011 06:00 to Sun 24 Apr 2011 06:00 UTC
Issued: Sat 23 Apr 2011 05:23
Forecaster: VAN DER VELDE

A level 1 was issued for Algeria and Tunesia mainly for large hail.

SYNOPSIS and DISCUSSION

Slight low pressure at surface level stretches from a low pressure center over the Iberian peninsula over France, Benelux and southern UK. The airmass is slightly unstable with a few hundred J/kg MLCAPE and weakly capped, except over The Netherlands. The maximum is predicted by GFS near the Belgian-French border of about 1000 J/kg. Central Europe also shows some unstable spots, the most significant being the Poland-Lithuania corner, associated with a distinct PV feature.
Shear conditions are benign and most likely result in single cell storm mode with a few multicells, but the combination of reasonable CAPE, steep mid level lapse rates and relatively cold LCL level could yield an isolated marginally large hail event around Belgium, if a storm manages to develop.
Deeper in Algeria unstable conditions and a strong convergence zone are present, with additionally a strong jetstream aloft, with vertical shear vectors >20 m/s favorable for supercells with a chance of large hail.