CONVECTIVE FORECAST - UPDATE
VALID 14Z FRI 16/07 - 06Z SAT 17/07 2004
ISSUED: 16/07 15:07Z
FORECASTER: VAN DER VELDE

There is a slight risk of severe thunderstorms forecast across Northern Russia

General thunderstorms are forecast across France, Nrn Spain, Nrn Italy

SYNOPSIS

DISCUSSION

...France...
Current dewpoints 15-16 degrees after mixing of the morning boundary layer. 12Z soundings indicate enhanced midlevel lapse rates and dry air, inhibiting layer, but with temperatures of almost 30 degrees and more mixing along with lift from orography the cap has broken over the Cevennes, Pyrenees, western Alps and Nrn Spain. Around 1000 J/kg CAPE may be released. Shear is almost absent, especially in the lower 3 km, as is a decent trigger, so storm longevity is short.

The cells may be accompanied by strong gusts very locally due to evaporational cooling through the dry air aloft; and marginally severe hail. As shear increases somewhat towards the evening (10 m/s DLS) and cold pools merge, a few clustered storms may happen.

GFS UVVs, instability and convective precip indicate potential for morning clusters/MCS over Nrn/NErn France, accompanied possibly by strong gusts.

...Nrn Spain...
12Z Madrid sounding has an inverted-v shape and CAPE, that indicates a potential for dry microburst with the isolated high-based shallow storms that occur - severe gusts possible at a very local scale.

...Nrn Russia...
East of Finland, the Kargopol 12Z sounding indicates 1200 J/kg MLCAPE, steep lapse rates, a dry midlevel layer and some 15 m/s deep layer shear. Strong multicells/MCS seem the main threat. The area already has thunder since the morning. The trigger seems to be a warm front with an upper trough providing lift through CVA. A potential for large hail and severe gusts exists and are thought to be widespread enough for a SLGT risk.

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