Storm Forecast
Valid: Sat 14 May 2016 06:00 to Sun 15 May 2016 06:00 UTC
Issued: Sat 14 May 2016 06:11
Forecaster: TASZAREK

A level 1 was issued for S Romania, SE Serbia, FYROM and Bulgaria mainly for the large hail and in lesser extent for severe wind gusts.

A level 1 was issued for W Latvia, W Lithuania, Kaliningrad Oblast and part of NE Poland mainly for excessive precipitation.

SYNOPSIS

Most of the W, S and E Europe is covered with polar warm air while tropical mass is pushed aside over Africa and E Mediterranean. On their border a subtropical jet stretches from Tunisia trough Greece, Black Sea up to S Russia. Polar jet is fragmented over far N Europe due to high extending over British Isles and long-wave with axis stretching from Svalbard up to CNTRL Europe. Increased jet flow runs from Iceland up to Benelux. Most of the SW Europe is covered with 1020-1025 hPa ridge mostly inhibiting DMC. A broad low on the right flank of the long wave provides advection of a warm and moist airmass from Black Sea area up to Baltic countries and E Europe. A remaining cold-mid levels due to a vanishing cut-off over SE Europe (and partly overlapping with a subtropical jet), provides a steep temperature lapse rates.

DISCUSSION

...S Romania, SE Serbia, FYROM, and Bulgaria...

Thanks to cold air remaining at mid-levels the development of a steep vertical lapse rates overlapping with 7-9 g/kg mean layer mixing ratio results in a CAPE up to 1000-1500 J/kg over a portion of SE Europe. At a SE edge of this area (Bulgaria), a jet streak with DLS up to 20-25 m/s runs WSW-ENE. Although in the most of the profile a shear is indirectional, a S/SW low-level advection provides a SRH up to 100-200 m2/s2. Given the possibility of the supercell thunderstorms, steep lapse rates, and a lowered elevation of 0C isotherm thanks to cold mid-levels, a threat for large hail up to 3-5cm exists. Area covered with level 1 threat receives a convective triggering factor thanks to the well-pronounced PVA in the afternoon hours. The best conditions for supercells fall on the area of S and E Bulgaria, however due to a CIN up to 50-100 J/kg extending on this area, CI remains uncertain. It cannot be also ruled out that thanks to undirectional shear and MLS exceeding 15 m/s, convection will cluster into a linear feature and pose a more pronounced threat for the severe wind gusts. Tornado threat is limited mainly due to a weak low-level wind shear. LLS increases in the evening hours over E and SE Bulgaria, but remains in a weakly unstable airmass and outside CI zone.

...SW Latvia, W Lithuania, Kaliningrad Oblast and part of NE Poland...

Although a CAPE thanks to poor lapse rates will remain low, a rich boundary layer moisture content (> 10-11 g/kg) and high PW values (> 30 mm) along with weakly sheared environment and thus slow storm motion, pose a threat for excessive precipitation. A signal of a southern PVA in the afternoon hours will help to initiate thunderstorms which in the form of a traning mode will pass an area covered in level 1 threat. A superimposing convective and large-scale precipitation may result locally in a sum up to 80-100mm.