CONVECTIVE FORECAST
VALID Mon 06 Jun 06:00 - Tue 07 Jun 06:00 2005 (UTC)
ISSUED: 05 Jun 20:45 (UTC)
FORECASTER: GROENEMEIJER

There is a slight risk of severe thunderstorms forecast across a part of Russia including teh adm. regions of Smolensk, Moscow, Tver, Yaroslavl and Vladimir .

SYNOPSIS

Monday at 06Z...a broad longwave trough over northern and central Europe amplifies. East of a frontal zone over eastern Europe, warm air is advected northward. Cental Europe is within an air-mass polar origin.

DISCUSSION

...SLGT risk area ...
A frontal zone is initially expected from eastern Bulgaria to near lake Rybinsk and further northeastward. A stable baroclinic wave is expected to move rapidly northeastward along the frontal zone. 500-1000 J/kg MLCAPE, perhaps slightly more in places, should be able to build along an axs east of the front. The wave and the associated upper-jet should...in combination with strong insolation provide the necessary ingredients, lift and latent instability, for convective initiation. The 0-6 km shear vector that has a magnitude of around 20 m/s has a strong front-parallel component, suggesting that the storms will rapidly cluster. A few short-lived bow-echoes are possible that may produce some severe winds. Additionally, there is a small threat of a few tornadoes as low-level shear is in the 10-15 m/s range, and LCL and LFC heights are forecast to be low. Isolated large (2-5 cm diam.) hail is a possibility as well.

...Poland, Czech Republic, Slovak Republic, Baltic States, extreme western Russia, Belarus and northwestern Ukraine....
Convection will probably reinitiate on a large scale in the polar air-mass. Rather low lifted condensation levels, generally below 1000 m, weak low-level winds shear and strong insolation between showers seem to provide rather favourable conditions for the formation of a few weak and short-lived "spout-type" tornadoes. The threat that those pose is marginal.

...central and western Balkans, central Italy...
A few 100s of J/kg of CAPE is expected to build over land areas in the region and weak capping should allow scattered storms to form during the afternoon. Deep-layer shear on the order of 15-20 m/s, and locally over 20 m/s in Italy, will promote the formation of well-organized multicell storms and perhaps one or two supercells. As a result, a small threat of large hail and gusty winds is expected. An upgrade may be issued if instability turns out to be stronger than currently expected.

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