Forecast Update
Valid: Thu 31 Jul 2008 13:00 to Fri 01 Aug 2008 06:00 UTC
Issued: Thu 31 Jul 2008 13:10
Forecaster: GROENEMEIJER

SYNOPSIS

Refer to convective forecast...

DISCUSSION

France

There is more certainty now about the convective evolution as the boundary layer has warmed to over 30 C in many places and dew points have risen significantly since yesterday evening. At 12 UTC, a weak surface trough extended along a line from near Rennes to Clermont-Ferrand. Near this trough dew point temperatures over 20 C are observed, that should yield between 1000 and 2000 J/kg MLCAPE.

Per VIS satellite imagery, convective initiation appears imminent over Normandy, Pays-de-la-Loire, Centre and Poitou. The presence of about 15 m/s of shear in the lowest 3 kilometres creates an excellent environment for the development of a strong linear, bowing convective system as inital convective cells merge. Given that the Paris and Bordeaux soundings at 12 UTC indicate dry air layers above the boundary layer in the lower troposphere, strong cold pools will likely form. Hence, damaging gusts are expected as well as localized large hail. As strong 10-15 m/s low-level (0-1 km bulk) shear is forecast to develop across NW and N-central France during the late afternoon and evening, a few tornadoes will be possible as well.

The storms will likely move to the NE or ENE during the afternoon and evening into north-central France and later into the Benelux and NE France. During the late evening the severe threat should gradually diminish as the boundary layer cools.

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