Storm Forecast
Valid: Sat 04 Nov 2017 06:00 to Sun 05 Nov 2017 06:00 UTC
Issued: Sat 04 Nov 2017 03:03
Forecaster: TASZAREK

A level 2 was issued for parts of NW Mediterranean mainly for large hail, severe wind gusts, excessive precipitation and tornadoes.

A level 1 was issued for W Mediterranean and NE Spain mainly for severe wind gusts, large hail and excessive precipitation.

A level 1 was issued for S-CNTRL France mainly for excessive precipitation.

SYNOPSIS

Ridge covers most of E, S and SE Europe. A long-wave travels eastward through W and SW Europe affecting British Isles, France, Iberian Peninsula and W Mediterranean. Jet stream stretches from Greenland to British Isles, and then up to N Scandinavia. The best conditions for organized DMC are located in W Mediterranean where enhanced boundary layer's moisture overlaps with EML from NW Africa and QG-lift associated with the passage of the trough.

...W Mediterranean...

An overlap of 9-10 g/kg MIXR with > 7.5 K/km lapse rates associated with EML advected from NW Africa ahead of the trough creates ML CAPE over water surface up to 1000-1500 J/kg. Over land in Spain and S France, CAPE is expected to be much lower (200-400 J/kg). Along with intensifying diurnal heating, a weak and isolated convection with occasional lightning should develop over Iberian Peninsula and S France in the afternoon hours, locally creating a threat for excessive precipitation, small hail and severe wind gusts. In the late evening and nighttime hours, trough axis will shift into waters of W Mediterranean and from now on convection should benefit from higher instability. Along with 15-20 m/s DLS and good lift, thunderstorms should organize into multicell clusters and then MCS. Lightning activity in the evening and during nighttime is expected to increase within these storms. A linear system capable of producing severe wind gusts is possible. Few supercells with a large hail and tornado/waterspout potential cannot be ruled out, especially along NE Spanish and S French coast where enhanced LLS (~ 10m/s) and SRH (> 150 m2/s2) will be available along with CI. Superimposing stratiform and convective precipitation in S-CNTRL France may also result in a few excessive precipitation and local flash flooding events. Eastwardly moving MCS should grow during nighttime hours over W Mediterranean and reach Corsica and Sardinia in the end of the forecast validity period.