Storm Forecast
Valid: Tue 26 Dec 2017 06:00 to Wed 27 Dec 2017 06:00 UTC
Issued: Mon 25 Dec 2017 23:20
Forecaster: DAFIS

A level 1 was issued for W France and NW Spain mainly for severe convective wind gusts.

DISCUSSION

A quite active weather pattern is forming in Europe the following days. During Tuesday 26/12 two troughs will influence W Europe, which will result in large-scale lifting of maritime air masses. Two more short-wave troughs will cross Italy and Balkans, also providing lift to unstable air masses, where several storms are expected mostly on Wednesday morning. Rather weak DLS will exclude extreme weather in Mediterranean Sea, but on the other hand, a low-level jet coming from the Atlantic will increase the potential of severe convective wind gusts. At the surface, two major cyclones will be found over Norway and the UK, accompanied by strong PVA signals in the upper levels. Storms should remain mostly offshore in the Gulf of Biscay, but GFS CAPE values over France and NW Spain suggest that storms could be fed also several kilometers inland. The main threat will be severe wind gusts as a 850 hPa jet shows wind speeds up to 30 m/s which can easily be translated to 20-25 m/s at the surface within thunderstorms.
The western parts of Italy and Balkans may experience locally strong storms after 00z on 27/12 which can produce excessive precipitation and strong wind gusts but spatial coverage of the events should be limited.