Storm Forecast
Valid: Sat 11 Jul 2015 06:00 to Sun 12 Jul 2015 06:00 UTC
Issued: Fri 10 Jul 2015 21:57
Forecaster: DAFIS

A level 1 was issued for parts of Germany, Switzerland, Austria, North Italy, Slovenia mainly for excessive rain, large hail and to a lesser extent severe wind gusts.

SYNOPSIS

A wide ridge extents from North Africa to Central Europe and high temperatures prevail in West Mediterranean. A low pressure system in NE Atlantic stays quasi stationary during this outlook between Iceland and the UK and a cold front crosses the British Isles during the morning, with some storms moving NE till noon.
Furthermore, another low pressure system associated with an upper air trough swirls in NW Russia, while a shortwave trough affects the Baltic states during Saturday.
In Central Europe a jet streak becomes visible during the second half of the Saturday where some storms may become organized.

DISCUSSION

....East Alpine region....

In south Germany signals of MLCAPE around 1000-1200J/kg according to GFS, mainly in Bavaria and DLS of 20m/s with locally up to 25 m/s later, indicate that any storm that pops up during the afternoon may become severe. WAA in lower levels may inhibit CI, something that ECMWF takes into account as CIN values exceed 50J/kg in addition to lower values of low level mixing ratio in contrast with GFS (~11g/kg). Other ingredients for severe storms will be the 15m/s 0-3km wind shear values over Austria and the SREH 0-3km that exceeds 150m²/s². Moreover, PW simulated by high resolution WRF runs, exceeds 30mm in the level 1 area, so excessive rain is a threat at the areas where low level convergence occurs. The strong 500-700hPa westerly winds will push the storms to the east after 18z, into a strongly sheared environment, so large hail events are not ruled out, whilst severe wind gusts will accompany these storms because of mid/low-level dry air. The tornado threat is low due to high LCLs and the weak LLS.


....Other areas....

NW Russia and the Baltic states will be under low geopotentials with a SW trough crossing the area. MLCAPE values of 1000J/kg cover a large area but deep layer shear is less than 10m/s, so the storms that will emerge due to diurnal heating will not become severe, but a local flash flood event is not ruled out as PW is almost 30mm.
In Sicily, very moist BL produce high MLCAPE values and convergence zones, enhanced by the sea breeze, may cause some flash flood events.
In NW Aegean Sea during the early morning, a convergence zone between Chalkidiki and Evboia island and LLS will produce a line of storms that might produce some waterspouts.