Storm Forecast
Valid: Tue 12 Apr 2016 06:00 to Wed 13 Apr 2016 06:00 UTC
Issued: Mon 11 Apr 2016 21:11
Forecaster: DAFIS

A level 2 was issued for SW France mainly for large to very large hail.

A level 1 was issued for parts of Portugal, Spain, France, Belgium and Germany mainly for large hail and severe wind gusts.

A level 1 was issued for Austria and S Germany mainly for large hail.

A level 1 was issued for Ukraine, Moldova and NE Romania mainly for excessive rainfall.

SYNOPSIS

A ridge of high pressure at mid and upper levels of troposphere is stretching from the Mediterranean into Central Europe. To the west a broad stationary cyclonic vortex advects warm air masses into continental parts of West Europe. Its center will be located NW of the Spanish coast with several impulses rotating around it. Another shortwave trough with its axis over Poland / Ukraine border will slowly move southwards on the forward flank of the ridge. At the surface, the main frontal zone will stretch from British Isles to West Mediterranean, with a warm front crossing southern France during the morning of Tuesday.

DISCUSSION

.... Portugal, Spain, France, Belgium, Austria and Germany ....

Latest model guidance suggest the development of up to 1000 J/kg of MLCAPE locally, over parts of France, under the jet stream. Deep layer shear (DLS) will be very strong under the mid-level jet, with values well over 30 m/s, as well as veering wind profiles will lead to the increase of SREH, so that more than 250 J/kg are possible. The surface heating should lead to the destabilization soon enough for storms to become organized and apart of a MCS or two in central France, a supercell is possible to emerge after 15z, due to the enhanced SREH values and strong shear, inside the level 2 area. Stronger cells will have the potential to produce isolated large hail, especially if supercells manage to form. This risk will probably quickly subside after the sunset with the diminishing instability. Quite moist air at low levels will result in low LCLs but LLS is expected to be very weak for potential tornadogenesis. Furthermore, the absent of strong forcing and SREH0-1km keep the tornado threat low. Storms over NE France, Belgium and Germany are not expected to have strong rotation, but the DLS overlaps with CAPE up to 800 J/kg, so a level 1 was issued for large hail, even though the LCL heights will also be low over this region.

.... Ukraine, Moldova and NE Romania ....

High resolution models produce about 1000 J/kg over eastern parts of Europe, where precipitable water is calculated around 30 mm. DLS will be weak, as well as the LLS, so we do not expect long-lasting organized storms, but strong cells could produce excessive rainfall and an isolated large hail event.