CONVECTIVE FORECAST
VALID 06Z SAT 08/05 - 06Z SUN 09/05 2004
ISSUED: 07/05 20:41Z
FORECASTER: DAHL

General thunderstorms are forecast across central ... western ... southern ... eastern and northern Europe.

SYNOPSIS

Scandinavian upper high is expected to weaken during the period ... with central-European upper low being progged to remain in place ... with several vort maxima rotating about its periphery. Main upper frontal zone is stretching from the Atlantic across Iberia across the S-central and E Mediterranean into SRN Russia ... over W Europe merging with the SE periphery of the central European upper low. At low levels ... weakening SFC low expected over the BeNeLux States at the beginning of the period will weaken during the day ... while large-scale low pressure region will persist over central and E-central Europe during Saturday.

DISCUSSION

...Scandinavia ... Finland...
TSTMS will likely develop with diurnal heating over Scandinavia and Finland in weakly capped air mass. Soundings reveal deeply mixed/dry boundary layer ... and storms will likely produce strong outflow winds. Cold-pool formation may be favored owing to strong evaporative cooling of the downdrafts ... and a few TSTMS may briefly evolve into bowing short lines with a threat of marginally severe wind gusts. Weak vertical shear and minimal CAPE will limit allover severe TSTM threat though.

...NW and N-central Mediterranean...
In the polar air mass overspreading the W Europe and N Mediterranean regions ... cellular convection will likely form over France and the NW Mediterranean. Strong vort max crossing the NW and N-central Mediterranean during the day ... will likely augment the convection. 500 hPa flow should be in the 25 to 40 m/s range ... with 15 m/s at 850 hPa per latest MM5 run ... and though convection will likely be rather shallow ... shear should be sufficient for a few rotating updrafts ... posing the threat for marginally severe hail and brief tornadoes given quite low LCL heights. ATTM allover severe TSTM threat is considered too low for a SLGT ... but an upgrade may be required in later outlooks.

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