Storm Forecast
Valid: Thu 28 Aug 2008 06:00 to Fri 29 Aug 2008 06:00 UTC
Issued: Wed 27 Aug 2008 19:32
Forecaster: GATZEN

SYNOPSIS

West-east orientated jet stream from northern British Isles to southern Scandinavia and Russia is dominated by shorts-wave troughs travelling eastward during the period. A rather intense trough will move across Scandinavia into the Baltic States. A mid-level jet curves around the troughs base providing strong QG forcing over Finland, and deepening surface is expected over central Baltic Sea. To the south, weak upper trough over Adriatic connects to the northern trough and moves eastward. Over south-western Europe, upper ridge remains. Warm air mass spreads into Iberian Peninsula east of a cut-off low over the Atlantic.

DISCUSSION

Central and southern Balkans

To the south-east of an upper trough over Adriatic, rather warm air mass is present over southern Balkans. This air mass is characterized by rather steep mid-level lapse rates as indicated by latest Brindisi ascent, while boundary-layer moisture is also quite rich over southern Balkans. On THU, expect that instability will likely develop. Given some warm air advection east of the upper trough as well as low-level convergence lines in the range of hilly terrain and outflow-boundaries, initiation is forecast in the afternoon hours. Although vertical wind shear is rather weak, some veering in the lowest 3 km may support a few supercells that may produce isolated large hail. Thunderstorms are forecast to weaken after sunset.

Turkey

Latest soundings indicate an elevated mixed layer over Turkey and deep moisture at lower levels, resulting in CAPE around 1000 J/kg. On THU, daytime heating and weak height falls will likely result in CAPE around 1000 J/kg again. Some thunderstorms are not ruled out over the hills capable of producing isolated large hail. Thunderstorms will decay after sunset.