Storm Forecast
Valid: Thu 01 Jul 2010 06:00 to Fri 02 Jul 2010 06:00 UTC
Issued: Wed 30 Jun 2010 18:00
Forecaster: GATZEN

A level 1 was issued for northen Italy and the central Balkans mainly for large hail and excessive rain.

A level 1 was issued for northern Finland and north-western Russia mainly for large hail and tornadoes.

SYNOPSIS

A weak mid-level flow is present over Europe. Over the northern portions, a short-wave trough migrates north-eastward during the period. An intense Atlantic trough expands into the British Isles. At lower levels, rather weak temperature gradients are present over most regions. Warm air advection can be found especially over western Europe ahead of the approaching long-wave trough. At the eastern flank of the northern short-wave trough, a weak cold front migrates slowly into western Russia. Rich low-level moisture can be found along this cold front as well as from the Black Sea region to the Balkans and Mediterranean except for Iberia. In the warm air advection regime of western Europe, rather rich low-level moisture is also present over France and the Benelux. Steep lapse rates are present over the Iberian Peninsula in the well-mixed warm air mass as well as to the east of the short-wave trough from Finland and north-western Russia to the western Ukraine. Over the Balkans and most portions of the Mediterranean, lapse rates are not too bad as well, and given ample moisture, CAPE will likely develop over a broad region.

DISCUSSION

Northern Italy to central Balkans

CAPE will likely build during the day given rich low-level moisture and relatively steep lapse rates. While the mid-level winds are weak, low-level support will be mostly relevant for initiation. Best potential seem to exist over northern Italy and over the central Balkans, where upslope flow will lead to low-level moisture pooling and convergence. Additionally, outflow-boundaries of Wednesdays storms will be supportive. Storms that develop do have a weak potential to organize, but given the slow motion, some storms may produce excessive rain fall. Additionally, pulse storms will pose a threat of isolated large hail. A low-end level 1 is issued for these threats. Storms will likely decay during the night hours.

Northern Finland

A tongue of warm air spreads into northern Finland in the morning hours. In the range of the cold front, latest models indicate a frontal wave that develops ahead of the slightly negatively tilted trough axis. This may be associated with some warm air advection during the day, and the low-level moisture may increase, while QG forcing will lead to some lift. A limiting factor may be the low-level buoyancy in the range of the cold front. Diurnal heating may be weak due to clouds and showers and the development of CAPE is not certain. However, current thinking is that at least weak instability will develop, and some thunderstorms are expected along the frontal boundary during the day. With moderate vertical wind shear of about 10 m/s in the lowest 3km and 15 m/s in the lowest 6km, some organized storms may produce large hail. Tornadoes are not ruled out given south-easterly surface winds and about 10 m/s low-level vertical wind shear over the eastern portions.