Storm Forecast
Valid: Sun 02 Jul 2006 06:00 to Mon 03 Jul 2006 06:00 UTC
Issued: Sun 02 Jul 2006 06:50
Forecaster: DAHL

SYNOPSIS

Not too much of a change expected at upper levels ... with an upper ridge remaining anchored over northern/central portions of Europe ... and low geopotential over SE and SW Europe respectively. Rather strong vort max will cross the Iberian Peninsula and S France late in the period ... being one focus for potentially severe convective evolution. Large SFC high is sprawling across NE Europe ... advecting rather dry air into the eastern parts of Europe ... while moist and unstable air is present over SRN parts of Europe. Weak cyclogenesis over Spain ... France and the W Mediterranean should accompany the Iberian upper trough in the late evening hours.

DISCUSSION

British Isles

GFS maintains development of precip across the British Isles ... due possibly to LL frontogenetical forcing and weak DCVA. Soundings should become weakly unstable during the day ... so that scattered TSTMS should be possible. Shear will likely increase towards the north ... where 20 m/s DLS should be available. Expect a few multicellular storms capable of marginally severe hail ... though an isolated mesocyclone cannot be discounted ... augmenting the hail threat.

Northern Iberian Peninsula ... SW France

Scattered high-based storms should develop over N Iberia ahead of the upper trough in the late afternoon/evening hours ... and spread into France during the night. Shear should be in the 15 to 20 m/s range ... and coupled with dry/deep CBLs this should promote threat of severe outflow winds ... though an isolated large-hail event or two cannot be ruled out either.

Storms may tend to become elevated however as they move into the Gulf of Biscay late in the day ... which should reduce the effective shear in their environment. However ... any storm that taps BL air over W France/E Biscay ... will have fair chances of becoming supercellular given stronly backed SFC winds. Main threat will be large hail ... but increasing LL shear may also promote a brief tornado or two.

Balkan States

The steep lapse rates across much of the Balkans have largely been mixed out ... yielding weaker CAPEs than on the previous days. However ... CAPE on the order of 1500 J/kg persists across the southern parts of the Balkans but minimal shear should limit organized severe TSTM threat. An isolated/brief large-hail event could occur if storms favorably interacted with the orography or outflow boundaries ... but this threat seems to be too conditional to warrant a categorical threat level.

Italy

Scattered TSTMS should develop in response to approaching upper vort max ... soundings across S Italy are reasonably unstable with MLCAPE on the order of 1500 J/kg. Organized severe threat should be limited by the absence of appreciable shear ... but e.g. orographic LL flow modification may promote LL wind profiles supportive of an isolated mesocyclone or two. Like over the S Balkans ... threat is too conditional for a categorical threat ... but an isolated large-hail/wind event could occur with the strongest cells.

Otherwise ... organized severe TSTM threat should be fairly low.