Storm Forecast
Valid: Sun 16 May 2010 06:00 to Mon 17 May 2010 06:00 UTC
Issued: Sat 15 May 2010 22:35
Forecaster: KOROSEC
A level 1 was issued for parts of NE Sweden, central Finland and parts of NW Russia mainly for marginally large hail.
A level 1 was issued for coastal areas of Montenegro, Albania, NW Greece and western Macedonia mainly for excessive convective rainfall.
A level 1 was issued for NE Bulgaria, extreme eastern Romania and south-central Ukraine mainly for large hail and severe wind gusts.
SYNOPSIS
A deep trough/upper low which brought a severe weather period across the southern Balkans finally fills while slowly translating northeastwards on Sunday. At surface, deep low with an attendant cold front weakens while moving towards central Ukraine. The surface front quite rapidly shifts eastwards off the Balkans onto the Black sea. The rest of Europe stays stable while mostly daytime driven convective activity is expected along the difuse frontal boundary extending from NW Russia into eastern Scandinavia, as well as within the quasi-stationary unstable airmass across parts of western Russia.
DISCUSSION
... NE Bulgaria, eastern Romania and south-central Ukraine ...
Convective activity will continue along the rapidly eastward progressing cold front, beneath the upper-level dvergence where strong forcing will remain in place. A few hundreds of MLCAPE seem reasonably available ahead of the surface boundary. Despite the position of the strong mid-level jet with deep-layer shear above 25m/s a bit south of the main instability release, it should allow storms to organize into multicells as well as a few rotating storms. Large hail and especially strong damaging winds seem like the main threat. Minor threat for a LL mesocyclones development seem over the Ukraine, however.
... coastal areas of Montenegro, Albania, NW Greece and western Macedonia ...
Strong westerlies with moderate to strong deep-layer exceeding 30m/s shear will again support strongly forced convection onshore into over the coastal areas of Albania and surroundings as well as more inland onto the complex topography. Marginal instability seem enough to support excessive convective rainfall locally. Persisting upslope flow and possible organized/maintaining storms could enhance the risk for local flash floods. This threat should diminish late in the afternoon when jet streak moves towards southeast.
... parts of NE Sweden, central Finland and parts of western and NW Russia ...
Mainly diurnal driven showers and thunderstorms are expected over parts of eastern Scandinavia and western Russia where somehow difuse frontal boudaries/LL convergence zones remain quasi-stationary. Latest soundings from western Russia showed rich BL moisture with mixing ratios near 10-11 g/kg. With strong diurnal heating and temperature insolation this should yield instability with MLCAPEs exceeding 1000 J/kg, though in only marginal shear. Numerous storms will take place with threat for marginally large hail across the level 1 area. More to the south, slow moving storms could support excessive convective rainfall locally as well. Given the high LL instability and weak wind field, funnels/spouts cannot be excluded either.
... southern Poland, eastern Czech Republic and northern Slovakia...
The situation over these areas will be most likely non-convective excessive rainfall, while minor chances exist for some embedded convection. Placed on the back side of the surface low, strongly forced upslope flow over Tatra mountains will support lots of stratiform rainfall which could result in total accumulations locally reaching or even exceeding 100mm per 24hr period. However, if some convective rainfall occur as well, higher accumulations are therefore even more likely. Local flooding can be expected over these areas.
