Storm Forecast
Valid: Sat 23 Mar 2013 06:00 to Sun 24 Mar 2013 06:00 UTC
Issued: Sat 23 Mar 2013 00:05
Forecaster: PISTOTNIK

No threat levels were issued.

SYNOPSIS

Behind a deepening trough over Eastern Europe, again very cold and dry air pushes South and West over large parts of Europe. Finally the resistance of a decaying Atlantic low results in a "delta" pattern with a sharp and stationary frontal boundary from the British Isles via Eastern France and the Alpine region to the Balkans. On the other side, the continental cold air gets attacked but not seriously endangered by the warm air advection shield of a powerful cyclogenesis near the tip of the Eastern European trough, which is coating the Eastern Ukraine and adjacent Russia.
While snow and freezing rain pose a hazard outside of the ESTOFEX forecasting scheme for these mentioned regions along the fringes of the enormous cold air body, the chances for thunderstorms are pushed back to Southwestern Europe, the last bastion of a seasonably mild air mass beneath rather low 500 hPa geopotential heights.

DISCUSSION

... SW-ern Europe ...

Cool upper levels allow the build-up of limited CAPE (<400 J/kg) over sea surfaces and, supported by diurnal heating, also over land. Isolated thunderstorms are possible throughout the forecast period over the Eastern Atlantic and mainly in the afternoon hours over Portugal, parts of Spain and Western France.
Weak deep-layer shear (10-15 m/s) should preclude any severe weather.

... Western Mediterranean ...

With light Southwesterly flow ahead of the broad area of low geopotential, the Western Mediterranean Sea will likely be capped by a weakly defined "elevated mixed layer" from Algeria during daytime, but persistent synoptic-scale lift support and increasing boundary layer moisture may be sufficient to break the cap and allow a few thunderstorms overnight. However, by then deep-layer shear will decrease enough to keep the severe weather risk very low, too.