CONVECTIVE FORECAST
VALID 11Z MON 04/08 - 06Z TUE 05/08 2003
ISSUED: 04/08 11:11Z
FORECASTER: DAHL

There is a slight risk of severe thunderstorms forecast across extreme W Russia.

General thunderstorms are forecast across Scandinavia and west-central Russia.

General thunderstorms are forecast across W Europe.

General thunderstorms are forecast across east-central Europe.

General thunderstorms are forecast across the south-central Mediterranean.

SYNOPSIS

Large quasi-stationary upper high is covering central and parts of southern Europe. Upper trough at the northern periphery of this high ... is crossing Scandinavia and the Baltic States during the forecast period ... closed quasi-stationary upper low is present NE of the Black Sea. Shallow cool airmass is advecting into the northern portions of central Europe ... while weakly unstable ... seasonably warm airmasses dominate the rest of the European continent.

DISCUSSION

...Extreme W Russia...
TSTMS have initiated along and ahead of a cold front within weakly capped airmass in DCVA-regime downstream of the Scandinavian upper trough. IR imagery suggests that only limited diabatic SFC heating will be possible given increasing coverage of TSTMS and mid/high level clouds associated with the UVV regime. However ... temperatures have climbed into the upper 20s and dewpoints are in the 14 to 18°C range ... possibly yielding CAPEs on the order of 500 to 1000 J/kg ... Deep-layer shear is on the order of 30 to 40 knots ... suggesting that primary convective mode will be multicellular storms the threat of hail and isolated damaging winds ... however ... enhanced SRH will likely be present along outflow boundaries ... and a small threat of supercells exists as well. These cells would pose a threat of primarily large hail.

...S Ukraine ... Moldavia ... Romania ...
Ahead of SE European upper low ... strong DCVA is expected to overspread the region. LRBS soundings and latest SFC OBS suggest that instability will be quite weak ... with CAPEs possibly below 500 J/kg. Expect TSTMS to increase in coverage over the next hours. Mesoscale wind field associated with the vort max is poorly represented by operational upper-air observations ... and some uncertainty exists with respect to the shape of the shear profiles. However ... indications are that shear will increase over the region during the day. Though the majority of the storms should be short-lived and rather weak ... brief organization into small lines appear possible ... posing the threat of marginally severe hail and strong wind gusts ... which may briefly approach severe levels.

...W Europe ...
High-based TSTMS will likely develop late in the day with peak heating over Portugal and W Spain ... aided by weak UVV's ahead of subtle vort max. TSTMS will likely produce strong outflow winds given very deep/dry subcloud layer. As this airmass is advected north across the Biscay into the British Isles ... TSTMS may spread north especially during the night when low-level WAA will be enhanced.

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