Extended Forecast

Extended Forecast
Valid: Sun 19 Jun 2016 06:00 to Mon 20 Jun 2016 06:00 UTC
Issued: Sat 18 Jun 2016 08:40
Forecaster: TASZAREK

This extended forecast is issued to highlight an elevated potential of severe thunderstorms over Balkan Peninsula on Sunday afternoon and evening hours. There is a risk of very large hail, damaging wind gusts, excessive precipitation and tornadoes.


On Sunday, Europe in mid-levels will be under influence of reversed omega pattern with ridges over SW Europe and Black Sea, and trough over CNTRL Mediterranean. Over the north, lows will be placed over N of British Isles and Scandinavia. In low-levels SLP will be more clearly divided into ridge over SW Europe and a lowering pressure bay over Balkans. A pressure over E Europe will start to increase and form a high over W Russia. Anticyclonically curved jet stream will be located over CNTRL Mediterranean with exit into W Balkans. Thunderstorms are expected on the southern flank of the developing high in W Russia and between trough over Italy where SE advection of a highly unstable tropical airmass will take place over Balkans.


...Level 2 and 1 areas...

Within a developing cut-off over Italy, an influx of highly unstable warm and moist tropical airmass will take place over Balkan Peninsula. An anticyclonically curved jet streak with DLS up to 25-30 m/s will cover instability areas with CAPE according to various model scenarios extending from 1500 up to 3000 J/kg. Thunderstorms are most likely to develop in the afternoon hours around 15-18 UTC thanks to lifting factors such as warm air advection, a slight PVA lobes, convergence areas and orographic lift. Because of uncertainties regarding CAPE magnitude, its placement, and range of tropical airmass influx and thus magnitude of CIN, NWP models do not agree with areas regarding CI. Some scenarios indicate CI on the border of Serbia/Bosnia and Herzegovina, CNTRL Serbia or SW Romania/E Serbia/NW Bulgaria. Currently the area of Serbia seems to be the most likely among all model scenarios, and therefore it is placed in the middle of our level 2. Western area consist of lower instability, while eastern has high CIN. After initiation, thunderstorm with the help of 300-400 m2/s2 SRH may quickly evolve into supercells capable of producing very large hail and damaging wind gusts. Thanks to strong airflow in low and mid-levels (MLS ~ 15-20 m/s), a clustering into linear features with bowing segments and damaging wind gusts cannot be ruled out. Given developing meso-low and thus favourable wind profile of curved hodographs with 100-200 m2/s2 0-1km SRH and > 10 m/s LLS on its eastern flank, a significant tornado event cannot be ruled out. In the late evening hours, convection may cluster into MCS that during nighttime will move northwardly towards W Romania, and fade due to sudden drop in instability. Level 1 area extending from W Ukraine up to Russia will remain under weakly sheared environment of < 10 m/s DLS, but a moderate to high CAPE that is predicted by the models may pose a threat of large hail up to 3-4cm and excessive precipitation given slow storm motion and very moist vertical moisture profile.

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