Forecast Update
Valid: Wed 21 Jun 2006 13:00 to Thu 22 Jun 2006 06:00 UTC
Issued: Wed 21 Jun 2006 12:38
Forecaster: GATZEN

SYNOPSIS

Low geopotential is present over western Europe ... with an axis from British Isles to central France and further to eastern Iberian Peninsula. While the southern part of this trough cuts off over SWrn Iberian Peninsula, central parts accelerate northeastward reaching Central Europe during the period. At the surface ... a convergence line has formed over western Poland ... southeastern Germany ... that is expected to shift eastward during the day and is expected to be the focus of severe activity.

DISCUSSION

Eastern Germany, western Poland, Czech Republic, southern Baltic Sea

Quite impressive thermodynamic profiles are indicated over parts of central Europe. An EML indicated by latest soundings spreads from SErn France to Alpine region and further to central Poland. At lower levels ... rich moisture ... with low-level mixing ratio of 10 to 14 g/kg ... is present from western Alpine region and northern Balkans to eastern Germany and Poland. As latest soundings indicate ... MLCAPE values of 1000 J/kg ... locally up to 2000 J/kg should be available over eastern Alpine region ... northern Balkans ... and parts of Czech Republic/Poland. In the range of a convergence line from western Poland to southeastern Germany ... thunderstorms are expected to go on over Saxony spreading into Poland ... while additional thunderstorms are likely to develop over western Poland/eastern Germany ... where numerous outflow-boundaries are present. Thunderstorms that form will have a potential to organize into multicells and supercells. Best chances seem to exist over western Poland and north of the Erzgebirge mountains ... where vertical wind shear should be strongest ... with 15 m/s DLS and about 7-10 m/s LLS. Large hail ... with isolated supercells probably very large hail ... and severe wind gusts should be possible. There will be also a chance for tornadoes including a few strong ones given low LCL heights and enhanced low level wind shear. Later in the period ... a few MCS should move NEward into central/eastern Poland/southern Baltic Sea region ... where intense precipitation and severe wind gusts as well as isolated large hail should be the most significant threat. Chance for severe storms should gradually weaken over eastern Germany ... where relatively dry airmass spreads eastward and should lead to low-level stabilization.

Southern Germany, Czech Republic

Low-level convergence has passed most of southern Germany ... where westerly winds are present. Due to strong diurnal heating ... expect that northerly low-level winds will develop north of the Alps ... leading to upslope flow. Given strong instability ... thunderstorms are expected to form near the Alps. These storms may organize given enhanced vertical wind shear north of the Alps. Although DLS is not impressive ... expect that isolated supercells pose a threat of producing large or very large hail as well as severe wind gusts. Chance for tornadoes should be also enhanced given quite low LCL heights and enhanced LLS. Storms should merge into an MCS moving eastwards into Czech Republic/Austria ... with severe wind gusts and isolated large hail the most significant threat.

Alpine region

Thunderstorms that form may organize into mesocyclones or multicells that will likely produce isolated large hail and severe wind gusts given strong instability. Although vertical wind shear should be weak ... a few supercells are expected especially over eastern Alpine region.