CONVECTIVE FORECAST
VALID 06Z SUN 25/04 - 06Z MON 26/04 2004
ISSUED: 24/04 16:33Z
FORECASTER: DAHL

General thunderstorms are forecast across the south-central Mediterranean regions and over much of eastern Europe.

SYNOPSIS

Central-European and Mediterranean upper cut-off lows will merge late on Saturday night ... resulting in one fairly extensive upper low settling over the central Mediterranean regions during Sunday. NRN-stream short-wave trough expected over the Baltic States at the beginning of the period ... is FCST to move SEWD and promote cyclogenesis along weak baroclinic zone over the belarus and W Russia towards the afternoon. SFC low over the Ionian Sea is progged to remain stationary ... with little change in strength during the period.

DISCUSSION

...Central Mediterranean...
Vort max will translate southwards at the W periphery of the developing central-Mediterranean upper low ... crossing the Tyrrhenian Sea ... moving into the Ionian Sea late on Sunday. Downstream vort max is expected to overspread the Aegean Sea and the S Balkans during the afternoon/evening hours. Saturday's soundings from the air mass over the central Mediterranean reveal a few hundred Joule of MLCAPE which may increase somewhat as DCVA-related UVV's overspread the region. Focus for TSTM development will likely be the SWWD progressing cold front ... the nose of wrap-around high theta-e's NW of the Ionian SFC low ... and orographic features over S Italy. Additional TSTMS should form over the southern portion of the Balkans in weakly capped environment ahead of vort max.

Deep-layer shear near the vort maxima is progged to be on the order of 20 to 25 m/s ... which will likely promote isolated marginal severe straight-line winds/hail.

There appears to be the tendency for the low-level moisture to become deeper towards the south of the central Mediterranean ... yielding nearly saturated boundary layers over portions of S Italy and the Ionian Sea ... any maybe also over Greece. In these regions ... chances for significant low-level rotation will be enhanced with any supercell that forms ... and a tornado or two may occur. However ... majority of the storms should be non-supercellular given weak large-scale low-level SRH.

...Belarus ... N Ukraine ... west-central Russia...
Weak CAPE should persist across E Europe and W Russia ... soundings show quite deep mixed boundary layers/high LCLs. As UVVs increase ahead of the short-wave trough ... TSTMS should form over the Belarus ... N Ukraine and extreme W-central Russia. 20 m/s deep-layer shear will be very marginal given only a few 100 J/kg of CAPE ... however ... dry BLs suggest that strong outflow winds will likely occur with the TSTMS ... which may organize briefly into short-line/bowing segments. Hail ... isolated approaching severe levels ... may also occur. Organized SVR TSTM threat is too low for a SLGT though.

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