Storm Forecast
Valid: Thu 14 Jun 2012 06:00 to Fri 15 Jun 2012 06:00 UTC
Issued: Wed 13 Jun 2012 22:26
Forecaster: GATZEN

A level 2 was issued for central Ukraine and western Russia mainly for large hail.

A level 1 was issued for Belarus and western Ukraine mainly for large hail and severe wind gusts.

A level 1 was issued for Central Germany and the Czech Republic mainly for large hail.

A level 1 was issued for Romania and Bulgaria mainly for large hail.

SYNOPSIS

Ahead of the central European long-wave trough, a strong SSWerly mid-level jet is still in place across eastern Europe. Another vort-max will travel north-eastward affecting the Ukraine/western Russia region. Farther west, the mid-level flow has weakened across the north Mediterranean. A short-wave trough will travel eastward during the period. Another trough will enter western Europe at Thursday.

DISCUSSION

Central Ukraine to western Russia

Along the rather broad frontal boundary across the Ukraine, warm air advection is forecast ahead of the approaching trough. An elevated mixed layer is still in place across eastern Ukraine and is expected to spread north-westward during the period. Latest GFS model run also indicates that rich low-level moisture will be present along and east of the frontal boundary. Even with weaker moisture, moderate CAPE is expected in the noon and afternoon hours.

Initiation is also forecast given rather strong QG forcing and low-level convergence. With strong 20 m/s 0-6 km DLS, multicells and supercells are expected to develop. These storms will have a potential to produce large or very large hail. Additionally, mean cloud layer winds along the frontal boundary are forecast to support the potential of excessive precipitation. Storms are forecast to cluster while moving north-eastward. Bowing lines are not ruled out given the strong mid-level flow, posing a threat of severe wind gusts. Increasing low-level vertical wind shear is also forecast to increase the potential of an isolated tornado in the evening hours.

Romania and Bulgaria

In the wake of the trough, the frontal boundary will move eastwards and some storms are forecast. Although deep layer vertical wind shear will decrease, a few large hail events are forecast given rather strong instability.

Slovakia, eastern Poland, and surroundings into Belarus

A rather well-developed short-wave trough will cross this region at Thursday. The affected air mass is rather unstable due to relatively rich moisture and high low-level lapse rates as indicated by latest soundings. Diurnal heating is expected to result in instability of some hundreds J/kg. Weak capping and low-level convergence will result in initiation during noon across eastern Czech Republic and Slovakia. Convection is forecast to spread into eastern Poland, western Ukraine, and Belarus during the day.

Weak vertical wind shear is expected over the western portions of this region. Where steep low-level lapse rates will evolve, isolated landspouts may occur. Additionally, pulse storms are forecast to produce locally large hail and excessive precipitation. Farther east, increasing DLS is forecast, and chance of organized storms increases. Large hail is forecast with the stronger storms. A tornado is not ruled out with isolated supercells especially in the evening hours when low-level vertical wind shear could slightly improve. Storms are forecast to cluster while spreading north-eastward, increasing the potential of severe wind gusts in the evening hours.

Central Germany into the Czech Republic

A 20 m/s mid-level jet streak will travel eastward with a short-wave trough. The cyclonically sheared flank will affect central Germany and the Czech Republic at Thursday. Rather moist profiles and improving lapse rates in response to diurnal heating are forecast and CAPE in the order of 500 J/kg is expected by latest GFS model. Current thinking is that storms will form during the day moving east. With strong DLS around 20 m/s, mesocyclones are not ruled out. Locally large hail and a tornado is not ruled out, but overall severe threat is rather weak. Storms will quickly decay after sunset.

Southern British Isles to northern France

Strong cyclogenesis is expected to the west of the British Isles at Thursday. Ahead of the low, a southerly flow and strong low-level vertical wind shear will evolve. Some storms may develop in the evening hours across northern France where low-level moisture is highest and CAPE is expected. These storms may produce a tornado given the strong LLS. Chance is rather limited, though. During the night, the cold front will cross the region from the west. Along the frontal rain band, some embedded convective cells are expected. The strong vertical wind shear could be beneficial for tornadoes, but bad timing and weak low-level buoyancy is expected to limit the potential.