CONVECTIVE FORECAST
VALID 06Z SUN 25/07 - 06Z MON 26/07 2004
ISSUED: 24/07 21:27Z
FORECASTER: DAHL

General thunderstorms are forecast across eastern Spain ... the central Mediterranean Regions ... SE and E Europe ... Scandinavia.

SYNOPSIS

Atlantic upper low is progged to shift eastwards into S Scandinavia during the period ... with main vort max at its southern periphery crossing portions of western and central Europe. Weak southern-stream vort maxima will continue to affect the central Mediterranean regions ... promoting weak cyclogenesis over the Tyrrhenian Sea/S Italy towards Sunday evening. Main ... slowly weakening ... SFC low will linger off the Norwegian W coast ... with the trailing cold front expected to extend from central Norway across the Baltic States and Poland into the N Mediterranean by Sunday midday.

DISCUSSION

...E Europe...
Air mass across most of E Europe is weakly capped ... but only modestly unstable with afternoon MLCAPEs in the 500 to 1000 J/kg range. However ... CAPE in excess of 2 kJ/kg in the Rjazan 27730 12Z ascent from Saturday suggests that CAPE is varying substantially within this air mass.

It seems that convective development will be tied to weak bands of DCVA in the vicinity of weak upper low present over and N of the Black Sea. Also ... boundary-layer features like outflow boundaries from Saturday's convection or orography will likely aid in TSTM initiation.

Mean shear profiles are expected to be very weak ... and allover severe TSTM threat should be quite low. However ... low-level shear will likely exhibit some variability as well ... and a small probability exists that regions of enhanced CAPE and enhanced low-level shear coincide ... which may result in a severe TSTM event or two. Severe threat is too conditional for categorical risk though.

...eastern Spain...
Spain will likely experience another round of high-based afternoon TSTMS ... given 10 to 15 m/s 0-6 km shear over N Spain ... and very dry deeply mixed boundary layers ... a few downbursts may occur. Coverage of these events should be quite low and a SLGT is not necessary ATTM.

...Italy...
As moisture depth is quite inhomogeneous over Italy ... degree of MLCAPE is difficult to ascertain. Based on model fields and on Saturday's 12Z soundings ... maximum CAPEs should be on the order of 1500 J/kg.

Shear will be enhanced at the periphery of vort max/developing upper cut-off low crossing the region during the day ... with 10 to 15 m/s 700 hPa flow. Given the mountainous terrain ... regions of enhanced low-level shear are likely to exist ... and some chances for a severe TSTM or two exists. Depending on TSTM coverage and on the presence of widespread ample CAPE ... an upgrade may be required on Sunday.

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