Forecast Update
Valid: Mon 18 Mar 2013 14:00 to Tue 19 Mar 2013 06:00 UTC
Issued: Mon 18 Mar 2013 15:00
Forecaster: VAN DER VELDE

An update to level 1 was issued for southern France mainly for chance of tornadoes and severe wind gusts.

SYNOPSIS

A large low pressure area is situated over western Europe with centers over the English Channel and northern Italy. Cool maritime unstable airmass advects deep into France. At the southern margin there is considerable overlap between CAPE and the jet stream and strong low level flow.

DISCUSSION

...southern France...

Currently, thundery convection has developed in the area. It lies directly under a 60 m/s jet at 300 hPa. Hodographs are large and slightly curved. The 0-6 km bulk shear reaches a very strong 40 m/s and 0-1 km shear over 15 m/s. Linear storms can develop bow echoes producing wind gusts over 25 m/s. Tornadoes are possible from embedded mesocyclones, LCL heights are favorable as well (500-1000 m).
The convective activity loses its energy as the sun sets (stabilization further increases low-level shear).