Forecast Update
Valid: Tue 18 Jun 2013 16:00 to Wed 19 Jun 2013 06:00 UTC
Issued: Tue 18 Jun 2013 16:55
Forecaster: PUCIK / GROENEMEIJER

SYNOPSIS

Refer to the original forecast

DISCUSSION

... Poland ...

Surface observations reveal that low level convergence has shifted more to the south than was expected in the original forecast. Poprad and Wroclaw soundings reveal moderately unstable airmass with notable vertical wind shear while soundings to the south reveal extremely unstable airmass along with weak vertical wind shear. Legionowo sampled mid and upper level jet observed just to the north of the warm front. Numerous severe thunderstorms have erupted and will likely be ongoing in the next few hours as the threat shifts more towards southeast. Very large hail and damaging wind gusts will be likely with more organised thunderstorms and there is still a possibility of storms to consolidate into an MCS towards the late evening / night hours with primary threat of severe to extremely severe wind gusts.

... France ...

It looks like thunderstorm activity streaming from S France towards north might have eventually become surface-based. Trappes 12 UTC sounding reveals very high values of 0-3 and 0-6km bulk shear with mostly unidirectional wind profile, while models simulate enhancement of SREH values towards the evening. With SSE-ly low level jet over the area, SREH values exceeding 300 m2/s2 are simulated while DLS values should reach between 30 - 40 m/s. In such environment, given the fact that storms are able root in the boundary layer, well organised DMC is expected, including long-lived supercells capable of (very) large hail, severe wind gusts and also tornadoes or bow echoes capable of isolated extremely severe wind gusts.

Only minor changes were made to other areas...