Storm Forecast
Valid: Sat 03 Dec 2016 06:00 to Sun 04 Dec 2016 06:00 UTC
Issued: Fri 02 Dec 2016 23:56
Forecaster: TASZAREK

A level 1 was issued for SW Spain, S Portugal, and NW Morocco mainly for excessive precipitation, tornadoes and in lesser extent for large hail.

SYNOPSIS and DISCUSSION

A broad long-wave covers N, NE, E and partly CNTRL Europe. It is surrounded by jet stream with 40-60 m/s wind speeds extending from Iceland through Poland, Ukraine and SW Russia. A blocking ridge stretches from CNTRL and W Mediterranean through W Europe and British Isles. A well-pronounced cut-off low with strong winds on its S flank is moving towards Iberian Peninsula.

A mixture of moderate mixing ratios (6-7 g/kg) and moderate lapse rates (~ 6.5 K/km) over weakly sheared CNTRL Mediterranean provide lobes of weak CAPE up to 200-400 J/kg. Due to shallow free convective layer and small cap, only an isolated thunderstorms with a small potential of lightning are locally possible in the Mediterranean basin. A local 2-3 waterspouts are not ruled out. Thunderstorm activity should increase during nighttime hours between Sicily and Greece.

Within approaching relatively warm low from Atlantic, an overlap of ~ 10 g/kg MIXR, ~ 6.5 K/km lapse rates, ~ 20 m/s DLS and QG-lift on SE flank of the low will create conditions for the development of severe thunderstorms. A favourable wind profile (~ 200-300 m2/s2 SRH) may trigger development of supercells capable of producing tornadoes and large hail. However, the risk of the last one is strongly limited due to the lack of good lapse rates. A superimposing large-scale and convective precipitation in the environment of 30mm PW create a threat of excessive precipitation and local flash flooding, especially in the late afternoon hours when convective precipitation will intensify.