Storm Forecast
Valid: Tue 07 Apr 2009 06:00 to Wed 08 Apr 2009 06:00 UTC
Issued: Tue 07 Apr 2009 03:21
Forecaster: VAN DER VELDE

SYNOPSIS

A frontal zone almost parallel to the flow at the east flank of a mid/upper level trough moves slowly eastward over Spain, France, Benelux, Germany, and southern Scandinavia. East of the front a slightly conditionally unstable airmass is present. Sufficient moisture in low levels and a source of lift will be critical for triggering of thunderstorms, in a subset of the area where the model pictures CAPE. Moisture is rather scarce and outflow will be cold, undercutting and suppressing convection by lack of shear. In the Mediterranean area, initiation will be much dependent on sea breeze fronts and mountains today.

DISCUSSION

...eastern Spain...

A low pressure area is forecast to form in the jet entrance region over eastern Spain. GFS forecasts strong destabilization which will result in multicells or a MCS, sustainable in a moderate deep-layer shear environment (15-20 m/s 0-6 km). There is a slight chance large hail may be reported, but helicity, moisture content and CAPE values seem fairly low so no threat level is issued. During the night, around the center of the low - predicted by GFS south and by ECMWF northeast of the Balearic islands, convective activity is likely to persist, which can lead to large accumulated precipitation amounts.

...northern Algeria...

Moderate deep layer and low level shear (15 m/s and 10 m/s) and mid level PV poking into decent instability appear favorable for development of organized storms, possibly a MCS of squall line type, suggested by Corfidi vectors. These may produce severe gusts and blowing dust.