Storm Forecast
Valid: Sat 26 Mar 2011 06:00 to Sun 27 Mar 2011 06:00 UTC
Issued: Sat 26 Mar 2011 06:03
Forecaster: VAN DER VELDE

SYNOPSIS and DISCUSSION

Under the influence of a large low pressure area over Scandinavia and Russia, cold air enters central parts of Europe from the north. In the warm airmass south of the cold front, in a band from southern Germany, over Austria, Hungary to Romania, slight CAPE is present and some thunderstorms can occur. Also over central France and northern Spain weakly capped instability and convergence zones present chance of local thunderstorms. The vertical wind shear and flow are weak, so storms will move slowly and are short-lived.

A more dynamic situation is present over western Spain and Portugal during late afternoon and evening, when the front side of a low arrives with a strong potential vorticity anomaly and quasi-geostrophic lifting. In mid levels a dry intrusion is found in theta-e fields. The GFS-predicted instability, though, decreases almost to zero as the sun sets. This might reduce convective potential to zero, but given the dynamic signals, potential instability, an increase of flow speed, 10 m/s low level shear, and 15 m/s deep layer shear, some marginally severe gusts cannot be excluded once a probably linearly organized storm would form. Storm-relative helicity seems insufficient for mesocyclone formation and tornado threat. Hence, support seems insufficient for a level 1.