CONVECTIVE FORECAST
VALID 06Z FRI 04/06 - 06Z SAT 05/06 2004
ISSUED: 03/06 16:56Z
FORECASTER: GATZEN

General thunderstorms are forecast across SEern Europe

General thunderstorms are forecast across central Mediterranean

General thunderstorms are forecast across Sern Iberian Peninsula

SYNOPSIS

Downstream of NEern Atlantic ridge ... European long-wave trough remains. Embedded cut-off is expected over the southern Adriatic on Friday morning. At the southern flank of this feature, moderately strong westerly jet streak will reach northern Greece, and UVM due to DCVA and WAA is forecast over the southern Balkans and Greece. Cold airmass will remain over the western Mediterranean and central, northern, and most of eastern Europe.

DISCUSSION

...SEern Europe ...
Focus of severe potential will be SEern Europe. Upper jet streak will rotate around the cut-off and overspread the region on Friday, where GFS model output suggests up to 60 kts SWerly winds @ 500 hPa. At lower levels, winds are forecast to back to SE just east of approaching cold front of Adriatic surface low. GFS suggests around 25 kts SSEerly surface winds over the Agean Sea. Weak instability will limit severe potential significantly over the affected region. GFS model forecasts suggest only some 100s J/kg CAPE east of the cold front due to relatively dry low-level airmass as confirmed by latest ascends. To the north, CAPE should also be limited as cloud coverage is expected to inhibit strong insolation. As the jet streak approaches ... rather strong synoptic forcing is expected ... and intense stratiform rain with embedded thunderstorms is forecast over the southern Balkans, spreading eastward. To the south ... thunderstorms may form along and ahead of the cold front. Rather strong vertical wind shear could be favourable for storm organization, and multicells or mesocyclones may form over Greece and the Agean Sea with isolated large hail and damaging wind gusts the main threat. Due to weak instability ... severe threat will be uncertain ... and a SLGT is not warrant at this time.

...Central Mediterranean ...
In the range of the upper trough ... airmass will likely destabilize during the day ... and CAPE may reach 500 J/kg due to GFS model output. Thunderstorms are forecast. Weak vertical wind shear will not support organized convection.

...Sern Iberian Peninsula ...
Steep lapse rates aloft and strong diurnal heating will lead to significant instability during the day. Orography may support initiation over southern Iberian Peninsula and thunderstorms should develop during the afternoon. Due to dry airmass ... strong downdraft winds will be possible, regional reaching severe limits.

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