Storm Forecast
Valid: Sat 19 Aug 2023 06:00 to Sun 20 Aug 2023 06:00 UTC
Issued: Fri 18 Aug 2023 22:04
Forecaster: PUCIK/KUZMENKO
A level 1 was issued across N Germany and Denmark mainly for severe wind gusts and tornadoes.
A level 1 was issued across Estonia, Latvia and W Russia mainly for excessive rainfall and large hail.
A level 1 was issued across N Slovakia and Poland mainly for excessive rainfall and to the lesser extent for large hail.
A level 1 was issued across S Bosnia, Montenegro, Albania mainly for excessive rainfall and large hail.
SYNOPSIS
A complex synoptic-scale setup is forecast across Europe. At mid to upper troposphere, southwesterly flow will have established across France and the UK in between of a ridge over Iberia and a low over the northern UK. A shallow low will be located over western Balkans and a subtle short-wave is forecast to move from Finalnd towards Estonia and W Russia in the evening hours. Closer to the surface, a frontal system is forecast to cross the Northern Sea into Denmark and Sweden. A stalling frontal boundary will remain across Estonia / N Latvia and Russia.
... N Germany, Denmark ...
A cold front is forecast to cross the area in the evening hours. Ahead of it, moist lower troposphere is forecast, but mid-tropospheric lapse rates will remain poor, yielding mostly skinny CAPE profiles, including stable layer in mid-troposphere according to some models. CAPE/shear overlap will be around the S fringe of the area and to the S of it. However, majority of models don't show any storms here, exception being ECMWF. Convection allowing models show almost no storms even over extreme N Germany. Hodographs are forecast to be mostly linear with 0-3 km bulk shear around 15 m/s across Germany, suggesting some potential for isolated severe wind gusts in case a squall line forms. Over Denmark, curved hodographs are forecast with 0-1 km bulk shear around 10 m/s and low LCLs, elevating the tornado threat. However it's uncertain whether the storms will be surface based here.
... Estonia, Latvia into Russia ...
Widespread thunderstorm activity is ongoing across the region at the time of the writing of the forecast (Friday 22 UTC). The activity will likely persist overnight with storms ongoing well into morning hours. The overnight activity will likely influence the exact location of the storms during Saturday by providing local lift through outflow boundaries or stabilizing the airmass over some regions. Models agree on the persistence of MLCAPE > 1000 J/kg along and south of the front and abundant MUCAPE north of the front. Storms will be initiated mostly by the stalling front and the activity will spread E during the day in conjunction with the passage of the short-wave trough at the upper troposphere. Shear will be weaker compared to the previous day, but may suffice to sustain large multicell clusters. Abundant CAPE in the hail growth zone will support isolated large hail. Heavy rainfall is also likely, given moist profiles and high moisture content in the lower troposphere.
... N Slovakia, SE Poland ...
Slow-moving storms capable of mostly heavy rainfall are forecast across the area. The storms will first initiate across the mountains and later on spread towards the lowlands. Large hail and downbursts will be more likely with the storms developing over the lowlands, where higher moisture content and higher CAPE values are forecast.
... Bosnia, Montenegro, Albania ...
Scattered to widespread storms are forecast to initiate over the mountains. Storms will pose threat of mostly heavy rainfall, given abundant moisture content and their slow motion. Large amounts of CAPE below -10 deg C suggest also elevated risk of large hail with the strongest updrafts.
