Storm Forecast
Valid: Thu 25 Jun 2020 06:00 to Fri 26 Jun 2020 06:00 UTC
Issued: Thu 25 Jun 2020 01:00
Forecaster: GATZEN

A level 1 was issued across northern Spain and northern Portugal across the Bay of Biscay into the south-western British Isles mainly for large hail and severe wind gusts.

A level 1 was issued across western France mainly for excessive precipitation and large hail.

A level 1 was issued across central Scandinavia mainly for large hail and severe wind gusts.

A level 1 was issued across western Russia mainly for large hail and severe wind gusts.

A level 1 was issued across the southern Russia into Georgia mainly for excessive precipitation.

A level 1 was issued across parts of the Balkans into Romania and Poland mainly for excessive rain.

A level 1 was issued across northern Algeria mainly for severe wind gusts.

A level 1 was issued across noth-western Austria mainly for severe wind gusts and large hail.

SYNOPSIS

A blocking ridge covers most of Europe, with a mid-level jet curving around it. A frontal zone extends from western Europe into Scandinavia and western Russia with some frontal waves embedded. Enhanced low-level moisture can be found close to these frontal waves especially across western Europe, central Scandinavia, and western/southern Russia. This moisture paerty overlaps with plumes of mid-level lapse rates across western Europe and central Scandinavia. A cut-off low is centred to the north of the Alps. A moist air mass across the Balkans and Poland is advected around the cut-off toards northern Germany.

DISCUSSION

Western Europe

Along the frontal zone with twi main frontal waves moving north, steep mid-level lapse rates are present. Elevated CAPE will be in the 1000 J/kg range and surface-based CAPE can develop during the day over the land. With moderate shear, multicells are forecast, capable of producing locally large hail and severe wind gusts. Over France, shear is weak, but increasing lift late in the period can result in storms spreading into the region with excessive rain the main threat, but some large hail is also not ruled out. Isolated storms are forecast across central Spain with large hail and severe wind gusts the main threat given moderate shear and inverted-v profiles.

Scandinavia

Models indicate some storms to form along the frontal zone in the afternoon. CAPE is limited but vertical wind shear is strong enough for storm organization. Multicells are expected with some large hail and severe wind gusts.

Western Russia

With a southward moving frontal wave, some storms are forecast in an airmass with marginal CAPE and modest vertical wind shear. Stronger storms can produce some large hail or severe gusts, however, overall threat is expected to be rather low.

Southern Russia

With northerly moist flow, some storms anchored to the mountains are forecast. These can produce locally excessive precipitation.

Balkans to Poland

Mostly uncapped, skinny CAPE in a moist and calm environment supports thunderstorms with a severe precipitation threat.

Northern Algeria

Deeply mixed airmass with some weak CAPE is present, and some local storms over the Atlas mountains are expected to produce local downbursts.

North-western Austria

In the wke of the cut-off low, a mid-level jet spreads into the Alps. Shear increases during the day with some southerly flow over the risk area atop of weak easterly winds. Lift along a weak warm front is expected. Main limiting factor is weak instability with rather dry conditions. However, some storms are forecast that can become brief supercells, capable of large hail and severe wind gusts.