CONVECTIVE FORECAST
VALID 06Z SAT 05/06 - 06Z SUN 06/06 2004
ISSUED: 04/06 19:37Z
FORECASTER: DAHL

General thunderstorms are forecast across the Iberian Peninsula.

General thunderstorms are forecast across east-central Europe ... the N Mediterranean and SE Europe.

General thunderstorms are forecast across NE Europe ... NW Russia.

SYNOPSIS

Eastwards progressing Atlantic upper trough will weaken west-European long-wave upper ridge during the period. Meandering ... upper frontal zone led by jet streak analyzed over the Nordic Sea on Friday 18Z ... is advecting eastwards ... resulting in narrow band of moderately strong upper WSW'lies reaching from the central Atlantic into N Russia by the end of the period. SE European upper trough is expected to remain in place ... exhibiting several disturbances at its periphery. At low levels ... cyclogenesis is forecasted over N Scandinavia beneath left-exit of the N-European jet streak. Weak low-pressure system will persist over the Balkan states beneath SW European upper low.

DISCUSSION

...Iberia...
With unimpeded insolation ... weakly unstable ... uncapped inverted-V profiles will likely develop late in the day ... supported by weak upper trough approaching them the west late in the period. GFS' Friday afternoon run suggests CAPE in the 1000 to1500 J/kg range. There are no indications that such amounts of CAPE will be realized on Saturday based on modified Friday 12Z launches. Nonetheless ... dry/deep sub-cloud layers will favor strong downdrafts ... and a few marginally severe straight-line winds may occur.

...S Balkans ... NW Turkey ...
Models agree in maintaining 10 to 15 m/s 850 hPa flow at the periphery of the low-pressure system over the N Mediterranean and the Balkans. Indications are that theta-e plume at the E flank of this feature will not promote much CAPE owing to weak lapse rates/low-level moisture. Nonetheless ... scattered TSTMS should be maintained throughout the period as QG upward forcing overspreads the plume. 0-1 km/0-3 km SRH will be maximized over the Bosporus region and over Romania with values ranging from 50 to 150 m2/s2 / 150 to 200 m2/s2 per GFS 12Z. Thermodynamic setup is uncertain at the moment. Nonetheless ... any storm that forms may pose the potential of acquiring updraft rotation ... leading to a slight large hail threat. Given relatively large 0-1 km SRH values ... an isolated tornado or two may occur as well ... especially late in the day when LCL heights decrease. Allover severe threat is too low for a SLGT ... due mainly to expected weak thermodynamic parameters. Otherwise ... organized severe TSTM threat should be quite low.

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