EXTENDED FORECAST
VALID 06Z TUE 24/06 - 06Z WED 25/06 2003
ISSUED: 23/06 21:28Z
FORECASTER: DAHL

There is a slight risk of severe thunderstorms forecast across SE Central Europe.

General thunderstorms are forecast across western and eastern Europe as well as across the northern Mediterranean regions.

SYNOPSIS

Intense vort max ATTM over NE Germany/Poland ... is expected to unify with a vort max indicated over the North Sea by WV imagery ... and to move into SE central Europe by the end of the forecast period. Southern-stream vort max at the moment reaching the Iberian Peninsula ... is progged translate NNE-ward ... reaching the western parts of France on Tuesday night. At low levels ... deepening low associated with the intense vort max is present over N-central Europe ... with the trailing cold front stretching from the Baltic Sea into N Iberia. The cold front is expected to continue SE into deep SE Europe during the forecast period. Ahead of the Iberian vort max ... weak cyclogenesis is forecast over the N Iberian Peninsula on Tuesday.

DISCUSSION

...Poland...north/central Belarus...
Convection should re-develop along the cold front over E Poland/W Belarus during the afternoon ... and along the warm front extending across W Russia/E Ukraine. DCVA-related ascent is expected to be somewhat weaker tomorrow than it was today over N Germany. Also, tongue of high low-level theta-e is expected to weaken within the occluding warm sector. GFS does not assume any surface-based CAPE across this region, but at least weak elevated CAPE should still be available. Given strong shear ... TSTMS should be capable of producing locally very gusty winds along with small hail.

...Slight Risk Area...

Farther S however ... airmass ATTM residing over the N Balkan states will be advected into the pre-frontal environment. LDDD/Zagreb 12Z ascent indicates very steep lapse-rates extending as high as 500 hPa ... and with 17°C low-level dewpoints, MLCAPE of about 2500 J/kg. Indications are that such high CAPE will likely not be available across all of the warm sector tomorrow. However, GFS's CAPE forecasts do not appear to be overdone ... which assume CAPE's on the order of 1000 to 1500 J/kg ... locally up to 2500 J/kg. Deep-layer shear on the order of 40 knots is anticipated over this region ... with substantial low-level veering expected ahead of a developing pre-frontal SFC low over S Ukraine ... Moldavia and E Romania.

TSTMS should initiate along and ahead of the cold front during the afternoon ... Majority of the storms should be multicellular ... primarily producing damaging wind gusts and possibly isolated large hail. Late in the day ... TSTMS should evolve into squall line possibly with embedded damaging-wind producing bow echoes.

A few mesocyclones are anticipated though, especially late in the day just W of the Black Sea where low-level veering is progged to be best. If 2000 to 2500 J/kg of CAPE can indeed be realized ... a few very large hail events may occur. Given generally high LCL heights ... tornado threat appears to be limited, though observations indicate quite a high moisture variability over this region ... and late in the day, low-level thermodynamic environment could locally indeed become favorable for significant low-level rotation. Best chances for a tornado or two appears to exist over S Ukraine ... Moldavia and E Romania where SRH should be highest.

...Spain...N Portugal...France...
High-based TSTMS should develop especially over northern Iberia along and ahead of the cold front during the afternoon as upper trough crosses the region. Given inverted-Vee type profiles ... and increasing vertical shear ... possibly as high as 30 knots in the lowest 6 km towards the afternoon ... some damaging wind events are expected. An upgrade to SLGT may be needed if TSTMS become more widespread than currently expected.

In the WAA regime over the Biscay and France ... development of an elevated MCS is expected late on Tuesday/Tuesday night. Shear in the cloud-bearing layer will likely be marginal ... but a few marginally severe wind gusts along with some hail may occur. Also ... threat of local flash flooding will exist.

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