Storm Forecast
Valid: Fri 21 Mar 2014 06:00 to Sat 22 Mar 2014 06:00 UTC
Issued: Thu 20 Mar 2014 23:14
Forecaster: TUSCHY

SYNOPSIS and DISCUSSION

An extensive Rossby wave settles over far NW Europe. Despite ongoing flattening of the large-scale high pressure area over S-Europe, a rather calm weather pattern persists over the Mediterranean. An exception will be a cold-core low over the W-Mediterranean, where environmental conditions become more favorable for a few thunderstorm events. Weak shear but 500-800 J/kg MLCAPE support a few pulsating and slow moving storms, which bring isolated large hail and heavy rain to NE Algeria and Sardegna. This activity decays until midnight.

EZ and GFS disagree with initiation over NE Spain and SW France. Marginal CAPE exists but forcing will be very weak. A short-lived and non-severe event can't be ruled out, but the coverage of this activity will be too isolated for a lightning area.

Widespread active marine convection occurs from Ireland to Norway. Brisk flow at 850 hPa and a well mixed subcloud layer point to strong/isolated severe wind gusts. A pronounced wave approaches Ireland during the afternoon hours with an increasingly veered BL flow. Atop, a coupled upper-level jet configuration adds some divergence, which could support rapid upscale growth into an area of stratiform rain with embedded convection due to the weakly capped nature of that air mass. This could lower the overall risk. Nevertheless more isolated thunderstorms stay in an environment with low LCLs and SRH-1 in excess of 200 m^2/s^2, which indicate a chance for funnels or an isolated tornado event. This risk extends from NW/N Ireland to W/NW Scotland. A level 1 was considered but meager CAPE and widespread initiation/rapid upscale growth of showers keep confidence below that threshold.