CONVECTIVE FORECAST
VALID Sat 11 Jun 06:00 - Sun 12 Jun 06:00 2005 (UTC)
ISSUED: 10 Jun 20:27 (UTC)
FORECASTER: dahl

SYNOPSIS

Upper low dropping SWD from Scandinavia ... and SE European upper low are expected to merge during the period ... creating quite extensive upper-low system reaching from Iceland to SE Turkey ... with several vort maxima present at its periphery. At low levels ... tongue of moderately warm/moist air mass is present E of the developing upper-low complex ... and peripheral vort max is progged to induce weak cyclogenesis at the SW edge of the theta-e tongue over the Ukraine ... being focus for potentially severe evolution ... though models are not quite in agreement on strength/positioning of this feature.

DISCUSSION

...central Ukraine ... E Belarus...
Friday's 12Z soundings across E Europe indicate weak instability in the theta-e plume ... disregarding the 33791 ascent (S Ukraine) which exhibits too cold mid/upper temps compared to upper-air analyses. Large-scale ascent ahead of vort max should support rather widespread TSTM development ... probably being focused in the vicinity of developing SFC low. Shear profiles should support a few severe TSTMS ... with 20 m/s 500 hPa flow ... and possibility of strongly increasing 850 hPa flow in the evening hours. Though primary threat should be marginally severe wind gusts ... with convective lines being the dominant mode ... mesocyclones could become increasingly likely in the evening hours if low-level shear increases as advertised by MM5. These may produce large hail and possibly a few tornadoes in addition to severe outflow winds. Uncertainty on strength of developing SFC low and low-level shear profiles precludes a SLGT ATTM.

...Iberian Peninsula...
Ahead of small quasi-stationary upper low ... scattered afternoon showers and TSTMS should develop over the Iberian Peninsula. Indications are that TSTMS will be rather high-based ... and that CAPE will be weak. Though shear should be quite meager ... isolated/brief severe outflow winds may occur given deep/dry CBLs. Storms may merge into one or more large clusters in the evening hours.

...central Europe...
Scattered showers will likely develop in polar air mass across central Europe ahead of vort max ... however ... it seems that convection will be quite shallow again ... and that TSTM activity will be limited. Will thus not introduce a TSTM area across central Europe ... though an isolated CG or two may well occur.

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