Storm Forecast
Valid: Sat 06 Aug 2016 06:00 to Sun 07 Aug 2016 06:00 UTC
Issued: Sat 06 Aug 2016 04:29
Forecaster: TASZAREK

A level 1 was issued for W Russia, NW Belarus, E Lithuania and E Latvia mainly for excessive precipitation, large hail, severe wind gusts and tornadoes.

A level 1 was issued for W Balkan Peninsula and CNTRL and S Italy mainly for large hail, excessive precipitation and severe wind gusts.

SYNOPSIS

Two highs are located over W Europe and W Russia and inhibit convective activity. Between them, a long-wave passes trough parts of CNTRL and N Europe. During forecast period, the axis of the wave is located along Scandinavia, Baltic Sea and N Poland. A low is spreading over N Scandinavia. A weakening cut-off is placed over Italy. Jet streak runs from British Isled, trough N Germany, Baltic Countries and NW Russia. Severe thunderstorms are possible on the eastern flank of the eastwardly moving long-wave and within a cut-off and its eastern flank.

DISCUSSION

...W Russia, NW Belarus, E Lithuania and E Latvia...

A well pronounced southerly warm air advection takes place in front of the eastwardly approaching cold front. Within 12-13 g/kg MIXR, ~ 6.5 K/km lapse rates and diurnal heating a CAPE in warm sector will develop up to 1500-2000 J/kg. Thunderstorms will develop along frontal boundary and fire up also in front of it. DLS in warm sector amounts 15 m/s and increases up to 20 m/s along frontal zone. Strong horizontal pressure and thermal gradient results in a strong flow and thus MLS (> 20 m/s) and LLS (> 15 m/s). Within such kinematics and linear forcing, convection will organise into line with bowing segments where severe wind gusts will be likely. A few isolated supercells and multicell clusters capable of producing large hail and excessive precipitation (given PW ~ 30-40mm) are possible to develop in front of the line. Due to strong LLS and veering wind profile (0-1 km SRH ~ 200 m2/s2) tornadoes within isolated supercells will be possible in the late afternoon hours. Thunderstorm activity should decrease in the evening hours when the CAPE will drop.

...W Balkan Peninsula and CNTRL and S Italy...

Within a rotating cut-off, a mixture of 10-12 g/kg MIXR and > 7 K/km lapse rates develops CAPE up to 2000-2500 J/kg. The highest values fall on the warm sector of the low's eastern flank. DLS extends mainly from 10 to 15 m/s with local lobes of 20 m/s. Within a good forcing, a numerous isolated and multicell clusters encircling the low will continue to be active during the whole forecast period and slowly shift southeastwardly. The main threat associated with these will be mainly related to large hail, excessive precipitation and local downburst/microburst severe wind gusts (elevated delta theta-e values). In areas with local DLS and SRH enhancement (up to 20 m/s and 150 m2/s2 respectively), a few isolated supercells capable of producing large hail cannot be ruled out. Thunderstorms developing on the W side of the Balkan Peninsula will pose a main threat of excessive precipitation.