Storm Forecast
Valid: Mon 16 Apr 2007 06:00 to Tue 17 Apr 2007 06:00 UTC
Issued: Sun 15 Apr 2007 22:24
Forecaster: GROENEMEIJER

SYNOPSIS

Monday at 06:00 UTC... a slack mid-tropospheric low remains situated over the western mediterranean region, while a weakening anticyclone over western continental europe weakens. A 20 m/s easterly jet at the 500hPa level flows in between those systems.

Srn France, Nrn Spain...

Relatively steep lapse rates exist over much of France. A capping inversion has in many places prevented the development of convective storms on Sunday, especially as mid/upper level support had been lacking. Exception has been the Massif Central where convective initiation is once again likely on Monday. The main convective activity is expected across southern France, where upslope flow over the Pyrenees and subtle forcing for upward motion by warm air advection will aid in removal of the cap. SBCAPE of 1000-1500 J/kg is expected which in combination with moderate 10 m/s deep-layer shear should prove adequate for the formation of multicell clusters with a threat of large (2-4 cm diameter) hail. Wind gusts are possible as well, but these are not likely to be particularly strong given the weak lower-tropospheric winds.

Wrn France, Srn Britain...

A small vorticity maximum over the Channel region will support upward motion over Brittany and southern England, likely leading to convective initiation in those places. A small threat of large hail exists. However, low values of instability and wind shear indicate suggests a threat below level 1 thresholds.