CONVECTIVE FORECAST
VALID 06Z SAT 13/03 - 06Z SUN 14/03 2004
ISSUED: 12/03 21:01Z
FORECASTER: DAHL

General thunderstorms are forecast across S Iberia.

SYNOPSIS

Current high amplitude upper flow pattern over Europe will become largely zonal towards the end of the forecast period ... with the Atlantic upper longwave trough closing off into an upper cut-off low over S Iberia/N Morocco late in period. Slowly eastward moving and de-amplifying large-scale upper ridge will cover the eastern parts of Europe with its axis stretching from the central Mediterranean into the Baltic States/NW Russia by Sunday 00Z. At low levels ... main feature will be vigorous WAA regime present over SW Europe ahead of the Atlantic trough/developing upper cut-off low.

DISCUSSION

...W and NW Mediterranean Sea ... E Spain ... S France...
NLY low-level flow has advected rather dry air across the central and W Mediterranean Sea ... with mean low-level dewpoints in the 3 to 7C range ... and the eastern portions of the developing broad band of SLY low-level flow over the W Mediterranean should struggle to become unstable during the day. The western part is expected to consist mostly of air originating from the subtropical Atlantic ... featuring somewhat richer low-level moisture. However ... degree of instability within this air mass is uncertain ... and confidence that significant amounts of CAPE will develop is rather low. Sheets of weak elevated CAPE may be present along and W of the low-level baroclinic zone E of the developing upper low ... but TSTMS will likely be too isolated to warrant a GEN TSTM area.

...S Iberia...
Beneath the upper thermal low associated with the cut off ... TSTMS will likely persist over the ocean ... and may spread into S Iberia during peak heating hours. Shear will likely not be particularly strong ... and given marginal CAPE ... organized severe TSTM threat should be quite low.

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