Storm Forecast
Valid: Mon 14 May 2007 06:00 to Tue 15 May 2007 06:00 UTC
Issued: Sun 13 May 2007 21:19
Forecaster: GROENEMEIJER

SYNOPSIS

At 06:00 UTC... a trough stretches from the Norwegian Sea to the Iberian peninsula. To the east of the trough a strong mid/upper-level jet stretches from NE France to SW Sweden. It is associated with a frontal zone in the lower troposphere. A shortwave trough is in the process of rounding the trough's base over S Iberia and the W Mediterranean.
In the regions ahead of the shortwave trough and in the right entrance quadrant of the aforementioned jet, upward vertical motion falls are expected to activate the cold front, resulting in widespread precipoiation over SE France, the W Alps and later across Germany.
To the west of the cold front a cool air-mass is present in which scattered thunderstorms should develop in reponse to diurnal heating.

DISCUSSION

S E Germany, Central Alps, Czech, N W Poland, Kaliningrad, Baltic States...

To the east of the front, that only slowly moves eastward, some latent instability should form, that is maximized along a prefrontal trough in the level 1 area. SBCAPE of up to 1000 J/kg is expected despite low-level moisture being relatively meager (surface dewpoints are expected to be in the 12-16 C range). Scattered thunderstorms are forecast to develop in the level 1 area in the afternoon in response to diurnal heating. Given the vicinity of the jet, strong deep-layer shear of about 25-30 m/s in the 0-6 km layer should be present. Initiating cells will therefore likely evolve into supercells, with a threat of producing large hail and possibly a few near-severe wind gusts.

N Italy...

During the late night and/or early morning, surface cyclogenesis and strong forcing for upward vertical motion are expected across northern Italy. These will likely lead to the development of some CAPE that is being released in storms. Severe threat should be rather marginal within the forecast period.