CONVECTIVE FORECAST
VALID 06Z SAT 19/03 - 06Z SUN 20/03 2005
ISSUED: 18/03 19:48Z
FORECASTER: DAHL

General thunderstorms are forecast across the western Iberian Peninsula.

SYNOPSIS

High-amplitude upper flow pattern existing over Europe ... with slowly E/NEWRD lifting Atlantic trough ... a ridge over W-central portions of Europe ... and a deep digging upper trough over NE Europe ... which is accompanied by deep continental polar/arctic air masses ... and which will continue to surge southwards ... covering most of E Europe by the end of the FCST period ... with strong low-level baroclinic zone stretching from the northern Black Sea across the western Balkan States and central Germany into the Nordic Sea by Sunday 06Z per GFS 12Z. Ahead of the Atlantic trough ... tongue of weakly unstable moist subtropical air mass is spreading NE ... reaching western Iberia late in the forecast period.

DISCUSSION

...France...
Models continue to generate CAPE over France in the afternoon hours. Firday's ascents indicate quite poor low-level moisture ... and FCST wind fields ... as well as current upstream low-level moisture ... do not suggest any increase of the moisture over France on Saturday. Also ... even if weak CAPE was to develop ... CIN on the order of several hundred J/kg would likely be present. Given negligible large-scale forcing for ascent beneath the ridge and no strong low-level boundaries ... convection is quite unlikely to be initiated. This is supported by available model guidance which does not advertise any precip over France on Saturday. Altogether ... TSTMS should be quite unlikely.

...W Iberia...
Current SFLOC data suggest that subtropical/Atlantic air mass is at least weakly unstable ... having allowed for scattered TSTMS on Friday. This air mass will spread into the extreme W Iberian Peninsula on early Sunday morning ... and chances exist that TSTMS will continue to occur in this air mass. Convection may tend to weaken some as the air mass spreads eastwards ... and severe threat is minimal. Nonetheless ... chance of a few lightning strikes exists ... marginally warranting a TSTM outlook.

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