Storm Forecast
Valid: Sat 16 May 2009 06:00 to Sun 17 May 2009 06:00 UTC
Issued: Fri 15 May 2009 22:45
Forecaster: DAHL

SYNOPSIS

Vort max ejecting from a quasi-stationary Atlantic upper low off the British Isles will cross N-central Europe on Saturday. A wavy low-level frontal zone is collocated with the E periphery of this upper trough, with this frontal zone stretching from NW Spain across W France into Poland on Saturday evening. A weakening upper low persists over the south-central Mediterranean. At low levels, a rather intense SFC low is accompanying the Atlantic upper low. Elsewhere, quiescent synoptic SFC conditions prevail.

DISCUSSION

... N Italy ... Balkan States ...

Mainly diurnally-driven thunderstorms should develop over the E Balkans as well as over N Italy. Shear seems to be somewhat marginal for an organized severe weather threat, but an isolated marginally severe hail/wind event cannot be discounted. However, severe probabilities should be too low to warrant a risk level.

... central France ....

Models agree in developing weak instability over central portions of France late in the day ahead of a vort max at the periphery of the Atlantic upper low. Deep shear will be on the order of 20 m/s, with LLS of up to 10 m/s possible. Currently, it seems that convection will remain too shallow for an appreciable severe threat. Should thermodynamic support become stronger on Saturday than currently anticipated, an upgrade may be necessary.