Storm Forecast
Valid: Sat 10 Jun 2017 06:00 to Sun 11 Jun 2017 06:00 UTC
Issued: Sat 10 Jun 2017 06:51
Forecaster: TASZAREK

A level 1 was issued for a corridor from SE Poland to Serbia mainly for the excessive precipitation and in lesser extent for large hail and severe wind gusts.

SYNOPSIS

Most of the Europe remains under weak horizontal pressure gradient and warm polar airmass. Weak 1020 hPa high overspreads CNTRL and W Europe. Mid-level ridge pushes into SW Europe. A shallow fading wave passes trough Poland. Large trough with shallow warm sector approaches British Isles. "Thermal convection" scattered thunderstorms with heavy rain potential are possible over parts of SE CNTRL Europe and Balkan Peninsula where enhanced lapse rates and rich boundary layer's moisture is available. However, due to weak forcing and rather shallow surface moisture layer CI over this area is uncertain.

DISCUSSION

...corridor from Poland to Greece...

Along with strong diurnal heating and evapotranspiration a 9-10 g/kg surface mixing ratios develops in the boundary layer. Combined with 7 K/km lapse rates creates a thermodynamic instability up to 600-800 J/kg (ML CAPE). SB CAPE values are much higher and oscillate around 1400-1600 J/kg, but due to shallow moisture layer, it may be unlikely for the atmosphere to release such energy. Thunderstorms should develop in the afternoon hours as a classical thermal convection. However, due to relatively weak QG-lift and dry layers above shallow boundary layer's moisture DMC is uncertain over this whole area. Originating updraft may evaporate and others may be kept by the cap. In the current scenario, the highest chances for CI may be along mountain ranges and within local converegence boundaries in the corridor from Serbia up to SE Poland. CI over SE Poland is more likely, since some lift will be available along with westerly PVA lobes. Due to weak vertical wind shear and rather limited strength of the updrafts severe weather potential is small and limited mainly to heavy rain within slowly moving pulse/multicell thunderstorms, and downburst type severe wind gusts. Local 2-3cm large hail event along Dinaric Mountains cannot be ruled out since DLS over this area will be enhanced to 15 m/s. Along with wind profile interacting with mountains, a 1-2 low-topped weak supercells cannot be ruled out. The main limitations for the whole aforementioned area are uncertain instability and questionable CI.