Storm Forecast
Valid: Mon 10 May 2010 06:00 to Tue 11 May 2010 06:00 UTC
Issued: Sun 09 May 2010 21:24
Forecaster: GROENEMEIJER

A level 1 was issued for parts of the Ukraine, eastern Belarus, and southwestern Russia mainly for large hail and extreme rainfall.

A level 1 was issued for parts of northwestern Russia manily for tornadoes and severe wind gusts.

A level 1 was issued for parts of southern and eastern France, and parts of Switzerland, mainly for extreme rainfall and large hail.


SYNOPSIS

An amplified trough is located over western Europe. An embedded vorticity maximum, associated with a weakening surface cyclone moves ENEward from the southern Bay of Biscay into France. Dowstream of this system, another vorticity maximum across the southern Baltic Sea moves northeastward across Finland, reaching the Kola Peninsula Tuesday morning.

DISCUSSION

Eastern Kola Peninsula, eastern Karelian republic, northern Archangelsk Oblast....

A frontal zone is almost stationary streching from the northern coast of Archangelsk Oblast across the White Sea to Lake Ladoga. As the Baltic vorticity maximum, which is complicated in structure, approaches, one or more MCS's will likely develop and travel northward along the frontal boundary. GFS has meso-beta scale SRH in excess of 200 m2/s2 and 0-1 km bulk shear > 15 m/s, indicating some tornado threat. Moreover, severe wind gusts may occur with the MCS's as convective downdraughts are enhanced by the preexisting horizontal momentum of the southerly low-level jet at 20 m/s. Low CAPE and limited prevents the issuance of a level 2 at the moment. The most active storms are expected to move northward across the eastern Karelian Republic during the afternoon and the may reach the eastern Kola peninsula in the evening.

Ukraine, eastern Belarus, southwestern Russia...

A frontal zone stretches from just east of St. Petersburg across western Russia, eastern Belarus to southern Moldova. Rising motion on the warm side of the frontal boundary and advection of warm air from the south leads to a weakly capped unstable troposphere. CAPE on the order of 1000-1500 J/kg is expected per GFS. Despite weak to moderate deep-layer wind shear, potential for a couple of large hail (2-4 cm) events will exist with multicell storms and some strong wind gusts are possible. Training storms are likely and high local rainfall accumulations may result in some localized areas. During the evening, the instensity of the storms will gradually diminish.

France, Switzerland ...

500-1000 J/kg of CAPE should develop during the morning and early afternoon as the vorticity maximum approaches from the west. First convection is expected to break out around or shortly after noon. Moderate shear and high convective coverage suggest a modest threat of large hail (2-4 cm) will exist. Upon clustering of the activity later in the day, aided by the approach of the upper-level system, very heavy rainfall may occur in a couple of places.