CONVECTIVE FORECAST
VALID Sun 29 May 06:00 - Mon 30 May 06:00 2005 (UTC)
ISSUED: 28 May 19:43 (UTC)
FORECASTER: DAHL

There is a slight risk of severe thunderstorms forecast across Germany ... W Poland ... W Chech Republic ... NW Austria.

There is a slight risk of severe thunderstorms forecast across the Baltic States and extreme NW Russia.

There is a slight risk of severe thunderstorms forecast across the central Balkans and the S Ukraine.

SYNOPSIS

As vort max currently over the Atlantic approaches the base of the large-scale Atlantic upper trough ... formation of a cut-off low over and W of Morocco is expected ... allowing the vort max to continue its eastward track into W-central Europe until early Monday morning. At Sunday 06Z ... strong low-level cold-frontal boundary associated with the large-scale trough should extend from W Spain along the continental-European NW coast into SRN Finland ... curving into the SFC low over the NRN North Sea. Warm front should stretch eastward from the SFC low center into the N Baltic States. Warm advection ahead of the approaching vort max is progged to promote weak cyclogenesis over central Germany late in the period. Frontal wave expected over the N Baltic States by Sunday midday ... is FCST to continue eastwards and eventually weaken late in the period. Otherwise ... synoptically quiescent conditions will persist.

DISCUSSION

...France...
Ahead of the Atlantic short-wave trough ... models are generating strong precip signals associated with isentropic ascent spreading across NW France ... Benelux and NW Germany during the period. Models suggest that bulk of this precip will be nonconvective ... which does not seem to be unreasonable given rather weak thermodynamic profiles over France. However ... a few elevated TSTMS may be imbedded. CAPE should be minimal ... but about 20 m/s shear in the cloud-bearing layer may support an isolated marginally severe hail event. Allover severe threat should be rather low though. Late in the night ... scattered TSTMS may develop along the front over central France ... degree of instability is rather uncertain ... and given the bad timing ... a SLGT is not necessary ATTM.

...Germany ... W Poland ... W Chech Republic ... NW Austria....
MLCAPE ahead of the cold front may climb into the 500 to 1500 J/kg range over Germany and Poland ... mainly depending on the depth of the BL moisture ... which has been quite shallow on Saturday. SFC convergence associated with developing low over SRN Germany in the afternoon hours should promote rather widespread convective development in the early evening hours. BOLAM suggests plume of high 850 hPa theta-e's over extreme E France and the SRN half of Germany to advect EWD and NWD during the night ... with increasing low-level flow. Associated maxima of theta-e advection should be focus for one or more MCS's that may develop in the late evening hours ... and persist through the night. Shear appears to be somewhat marginal ... but may support bowing segments and possibly an isolated mesocyclone or two ... with the main threats being large hail and damaging winds. Persistent stratiform precip/cooling NW of the frontal boundary may augment mesoscale temperature gradient across the front ... which could enhance the low-level wind field. Depending on the proximity of the precip to the developing MCS ... the timing of convective development and the intensity of the precip NW of the frontal boundary ... this may increase organized severe TSTM threat somewhat ... though this scenario is rather speculative ATTM. Altogether ... SLGT is marginally warranted.

...Spain...
Chance of a few TSTMS again exists over Spain ... though coverage is somewhat uncertain ATTM due mainly to the lack of 12Z sounding data from Saturday. Boundary layer will likely be rather dry and deeply mixed ... so that a few strong/severe convective outflow winds may occur. Uncertainty on the coverage of the TSTMS is currently precluding SLGT.

...Baltic States...
Strong deep-layer and low-level shear will likely accompany the frontal wave over NE Europe. Though CAPE may be somewhat limited ... a few severe TSTMS should be possible. Along the cold front ... primary severe-convective storm mode may be rather isolated supercells and bow echoes given that deep-shear vectors will have large front-normal component. Expect a few severe wind and large hail events though an isolated tornado or two are not excluded.

...central Balkans and the S Ukraine....
Another round of TSTMS is expected over SE Europe in weakly capped ... and weakly to moderately unstable thermodynamic environment. Large-scale shear will be marginal ... but various outflow boundaries should be in place ... capable of augmenting the low-level shear profiles locally. Expect again rather numerous cells to form ... some of which may coagulate into larger clusters late in the day. Though main threat should be local flash flooding ... a few large-hail and severe wind events may also occur. Weak/no CIN and low LFC heights may in addition support a brief tornado or two ... altogether marginally warranting a SLGT again.

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