NW, W and central France, BeNeLux...
Numerical models suggest that clustered convective activity will be ongoing over western France early on Monday. These storms appear to be associated with a maximum of warm air advection that is forecast to translate northeastward into the BeNeLux countries during the evening. The system, as simulated in the models is elevated and occurs on the cold side of an northward advancing surface warm front. This should mitigate the overall severe threat. Nevertheless, it is thinkable that some surface-based storms will develop as well, and benefit from strong deep layer shear (0-6 km bulk shear 25-30 m/s) and a strongly helical flow (300 m2/s2 storm-rel helicity). The environment would then be supportive of supercells with a risk of very large hail, severe winds and perhaps a tornado. Presently, this scenario is not supported by NWP models. With the elevated storms, severe hail should be the biggest threat. If confidence in the development of surface-based convection and/or in a high convective coverage increases, an update to a higher risk level may be warranted.
Numerical models suggest that clustered convective activity will be ongoing over western France early on Monday. These storms appear to be associated with a maximum of warm air advection that is forecast to translate northeastward into the BeNeLux countries during the evening. The system, as simulated in the models is elevated and occurs on the cold side of an northward advancing surface warm front. This should mitigate the overall severe threat. Nevertheless, it is thinkable that some surface-based storms will develop as well, and benefit from strong deep layer shear (0-6 km bulk shear 25-30 m/s) and a strongly helical flow (300 m2/s2 storm-rel helicity). The environment would then be supportive of supercells with a risk of very large hail, severe winds and perhaps a tornado. Presently, this scenario is not supported by NWP models. With the elevated storms, severe hail should be the biggest threat. If confidence in the development of surface-based convection and/or in a high convective coverage increases, an update to a higher risk level may be warranted.
