CONVECTIVE FORECAST
VALID 06Z SAT 08/11 - 06Z SUN 09/11 2003
ISSUED: 07/11 23:27Z
FORECASTER: DAHL

General thunderstorms are forecast across the Iberian Peninsula.

SYNOPSIS

Closed upper low ATTM at the S periphery of the N European upper high ... will continue westwards to be ingested by upper longwave trough approaching from the Atlantic. Associated SFC high centered over Scandinavia ... continues to advect dry polar air into major parts of the FCST area. Plume of subtropic/Atlantic airmass will affect Iberia and the Biscay during the period.

DISCUSSION

...Iberia...
Airmass advected into Iberia is not yet sampled by available radiosonde data ... but lightning data and numerical analyses suggest that airmass is at least weakly unstable. Appreciable DCVA is coherently simulated to overspread Portugal/Spain late Saturday afternoon/evening into the night ... in response to which a few TSTMS will likely form. Deep shear is expected to be on the order of 50 knots ... with relatively weak low-level wind fields. The strongest cells could produce some hail and strong wind gusts ... but chance of severe should be rather low.

A few isolated/shallow TSTMS could form across the Adriatic/Ionian Sea and over southern parts of Italy ... but coverage is expected to be too low for a general TSTM area.

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