Valid: Mon 01 Aug 2016 06:00 to Tue 02 Aug 2016 06:00 UTC
Issued: Mon 01 Aug 2016 04:41
Forecaster: VAN DER VELDE
A level 2 was issued for N/W Belarus, E Baltic states and W Russia mainly for severe convective wind gusts and tornadoes.
A level 2 was issued for Croatia, Bosnia and Serbia mainly for large hail and severe convective wind gusts,
A level 1 was issued from Italy to Greece to Romania, Ukraine and W Russia mainly for large hail.
A Scandinavian low is the center of a broad mid level trough moving over Europe with a strong westerly flow, pushing a cold front into Italy, Balkan, Ukraine, Belarus and the Baltic states, where a surface low and occlusion point moves northeastward from E Poland to NW Russia. Strong shear is found in association with this feature. A zone with 10-13 g/kg mixing ratio stretches out from Italty along this cold front, producing 500-1500 J/kg MLCAPE in GFS. A shortwave mid level trough moves over the central Balkan countries during the afternoon, causing weak capping under steep lapse rates.
A low altitude dynamic tropopause (1-2 PVU) is found at 12Z over the western Balkan including Slovenia, Croatia, Bosnia and Montenegro. With significant CAPE from the Adriatic Sea, these areas will be affected mainly in the morning while Serbia has the best lifting conditions ahead of this dynamic feature during the afternoon. Low cloud base heights are depicted by GFS over the western Balkan, whereas LCLs higher than 2500 m span the eastern Balkan (Greece to Bulgaria and S/C/E Romania). The high cloud bases offer support for broader updrafts with large to very large hail and severe wind gusts, helped by a moderate 10-15 m/s 0-6 km shear to organize the storms and create long-lived systems.
...Belarus, eastern Baltic states, western Russia....
From eastern Slovakia to eastern Estonia, a very humid frontal zone is present with significant MLCAPE to its east. In some locations along this zone, excessive rainfall may occur as different storms could pass over. The low pressure system is supported by a shortwave trough, both moving rapidly NNE-ward with 1-3 km average wind speeds of 20-25 m/s east of the low. Forecast GFS hodographs are large and extremely veering with height, although the maximum occurs north of the occlusion point outside the CAPE zone. Through the CAPE zone, 0-3 km SREH of 150-250 mē/sē and 0-6 km shear of more than 15 m/s support supercells which can be accompanied by tornadoes, perhaps a significant one, supported by 0-1 km shear values of 12-16 m/s. These numbers also occur south of the low pressure center, over N Belarus, where triggering by the cold front should rather organize storms into a squall line with a severe wind gust threat. Large hail is also likely. These storms will move into W Russia, but GFS diminishes the CAPE as the low moves towards the north, and the episode may end shortly after nightfall.