CONVECTIVE FORECAST
VALID 06Z SAT 07/08 - 06Z SUN 08/08 2004
ISSUED: 06/08 21:02Z
FORECASTER: DAHL

General thunderstorms are forecast across W ... central ... S ... E and N Europe.

SYNOPSIS

Large-scale upper trough over the N Atlantic remaining in place through the period ... with weak upper frontal zone covering the Mediterranean Sea. Weak upper low will persist over SE central Europe ... with high geopotential building over C Europe. Weak trough ejecting from S periphery of Atlantic trough is expected to cross N Iberia and France on Saturday ... other vort max downstream is FCST to affect the Aegean Sea and Turkey. At the SFC ... extensive high pressure area is present over NE Europe and Russia ... advecting relatively dry low-level air into NE portions of central Europe. Increasing SLY low-level flow is progged to spread into extreme W Europe in response to intense cyclogenesis over the Atlantic. Otherwise ... quiescent conditions persist.

DISCUSSION

...Central Europe ... England/Benelux ... SE-central Europe/N Balkans ...
Weak CAPE is expected to persist across large parts central Europe on Saturday ... generally ranging from 500 to 1000 J/kg. Storms should initiate mainly in response to diurnal heating along small-scale boundary-layer features like old/weak outflow boundaries and/or weak baroclinic zones apparent in the 850 hPa theta-e analyses. Mid/upper flow will likely be quite weak ... with maximum values of 10 m/s at 500 hPa over SE central Europe and the Balkans at the periphery of weakening upper low ... the British Isles ... extreme W Germany and Benelux are expected to be overspread by 10 to 15 m/s 500 hPa flow towards late Saturday. Though majority of TSTMS will likely struggle to organize ... an isolated marginally severe hail/wind event or two could occur if cells favorably interact with outflow boundaries etc. However ... allowever severe TSTM threat is quite low.

...S France...
Best kinematic/thermodynamic setup will likely evolve over S France. Increasing SLY low-level flow should advect somewhat richer moisture into the region ... and CAPE should generally be several 100 J higher than over central Europe. 10+ m/s 500 hPa flow ... and DCVA-related UVM overspreading France during the afternoon/evening should support a few multicellular storms ... capable of producing strong wind gusts and some hail ... and large amounts of precip ... if confidence in large TSTM coverage increases ... an upgrade to SLGT may be necessary.

...Spain ...
About 20m/s mid-level flow will overspread inverted-V type thermodynamic profiles over Spain ... TSTMS should initiate late in the day ... aided by SRN fringe of French DCVA-regime. Coverage remains somewhat uncertain ATTM ... but threat for severe straight-line winds exists. Large TSTM coverage would likely favor rapid cold-pool formation with a threat for high-based bow-echoes and an upgrade may be needed if large TSTM coverage materializes.

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