Storm Forecast
Valid: Thu 11 Apr 2013 06:00 to Fri 12 Apr 2013 06:00 UTC
Issued: Wed 10 Apr 2013 20:35
Forecaster: GATZEN
SYNOPSIS / DISCUSSION
A long-wave trough enters Europe from the west. Ahead of this trough, a strong mid-level jet across Spain and France will spread into the west Mediterranean and Germany. Warm air advection takes place especially ahead an occlusion that crosses Germany.
In the wake of the occlusion, a frontal boundary that becomes nearly parallel to the flow will extend towards the Bay of Biscay and moves slowly southward. Low-level moisture will be augmented along this frontal boundary across central and southern France, where low-level mixing ratio exceeds 8 g/kg.
Mid-level lapse rates will be poor at the same time, but diurnal heating may result from some sunny spells in the wake of the Pyrenees that enables weak CAPE ahead of the cold front.
Some showers and thunderstorms are not completely ruled out there, but overall chance seems to be too low for a thunderstorm area. However, if storms indeed will form, they may quickly become supercells given strong vertical wind shear (20 m/s 0-3 km bulk shear) and large hodographs (SRH 200 mē/sē). Large hail and tornadoes are not ruled out if storms can develop in the afternoon hours.
Behind the cold front, the trough enters France and the southern British Isles where lapse rates will become steeper. A few storms are not ruled out but weak moisture and low-level stabilization in the evening hours will limit the thunderstorm chances. An isolated hail or wind event is not ruled out given the strong vertical wind shear, but chances are too weak for a level 1 area.
