CONVECTIVE FORECAST
VALID 11Z FRI 12/03 - 06Z SAT 13/03 2004
ISSUED: 12/03 11:22Z
FORECASTER: VAN DER VELDE

General thunderstorms are forecast across NW Spain, W France, Ireland

SYNOPSIS

In SWLY upper air flow, a sfc low will develop along the Atlantic occlusion at the left exit of the upper jet and the nose of a theta-e plume and translate NNE-ward from the entrance of the English channel over the eastern UK. Behind the cold front the airmass is unstable and allows convection deep enough for occasional thunder.

Another sfc low is filling up under increasing 500 hPa heights near Greece. The current thunderous convection is expected to cease due to the effects of subsidence.

DISCUSSION

...NWRM France...
Just south of the developing sfc low, low level pressure gradients are pretty steep and 0-1 km shear is expected to reach over 10 m/s. This combined with deep layer shear (0-6) over 30 m/s and LFCs below 700m and some instability may pose a chance for an isolated tornado if any convection organizes within the sfc convergence zone. High shear conditions and linear forcing at the cold front may set the convective mode favorable for a squall line which may have bow echoes, however, instability and 850 hPa winds for gusts at the SFC are not expected to that high to warrant a SLGT risk.

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