Storm Forecast
Valid: Mon 08 Sep 2008 06:00 to Tue 09 Sep 2008 06:00 UTC
Issued: Sun 07 Sep 2008 22:17
Forecaster: GROENEMEIJER

SYNOPSIS

A ridge stretches from northern Scandinavia to the Central Russian Uplands. From the west it is followed by a
a trough that intially stretches from the German Bight to the Czech Republic to central Italy. It should reach Belarus on Tuesday morning. A well defined cold front precedes it, replacing a warm and moist air-mass with a much drier and cooler one.
In the wake of the trough a broad ridge builds over southwestern Europe. West of its axis, some destabilization is expected to occur in a warm advectuon regime, which will probably lead to some elevated thunderstorms in a zone from western Iberia into southwest France in the night to Tuesday.

DISCUSSION

NE Poland, Belarussian Oblasts of Grodno and Vitebsk, E Lithuania, E Latvia, SE Estonia, Russian Oblast of Pskov...

Ahead of the cold front, a rather narrow zone of moist air is advection northward by a strong low-level jet. In the range of this low-level jet, 0-1 km shear should be on the order of 10-15 m/s while deep-layer shear of about 20 m/s is expected. As about 1000-1500 J/kg MLCAPE develops during the day, some thunderstorm will likely develop on a prefrontal convergence zone. Because shear is almost front-parallel, the storms will likely not remain isolated very long. Still, the possibility of a few strong rotating storms will exist initially, with a threat of isolated large hail and perhaps a tornado. Severe winds gusts will also be possible. Gusts will remain possible with the clustered convection that will probably develop rather quickly. The severe threat should diminish during the late evening as the boundary cools and the remaining convection becomes elevated.

German Bight...

In vicinity of a decaying mid/upper-level low over the North Sea, showers and isolated thunderstorms will likely be ongoing for most of the daytime before gradually decaying from the west in the late afternoon and evening. Ample ambient horizontal vorticity and a moist boundary layer, a few waterspouts may occur.