Storm Forecast
Valid: Sat 04 Jun 2022 06:00 to Sun 05 Jun 2022 06:00 UTC
Issued: Fri 03 Jun 2022 20:52
Forecaster: GROENEMEIJER/PUCIK
A level 2 was issued across a large part of France and for northern Spain for (very) large hail, severe wind gusts and very heavy rainfall.
A level 1 was issued across western France, the UK, southern Benelux and western parts of Germany primarily for very heavy rainfall, and secondarily for a risk of isolated severe wind and hail.
A level 2 was issued for the Alps and Alpine forelands for large hail and severe wind gusts as well as very heavy rainfall.
A level 1 was issued for large hail, heavy rainfall, and severe wind gusts across parts of Poland, Czechia, Hungary West Ukraine and the Balkan countries.
A level 1 was issued for large hail and severe wind gusts over parts of Türkiye and the Caucasus region.
A level 1 was issued for parts of East Ukraine and Russia for heavy rainfall and large hail.
SYNOPSIS
An active convective weather pattern is forecast across Europe. In the mid to upper troposphere, a deep low will reside over the Atlantic and a trough is forecast to lift from W Iberia towards France. Further north, a trough will move from South Sweden and Denmark to the Baltic states and Poland. A shallow, quasistationary low is centered SW of Türkiye.
Closer to the surface, a complex frontal zone will run from Iberia through W France into Belgium, central Germany, Czechia, Slovakia, Ukraine and Russia. Along and just south of the frontal zone, a moist boundary layer is forecast with mixing ratios around 12 g/kg. A complex, slack surface low is located near Brittany. On its southern flank, across Southwest France, increasing westerly winds that bring somewhat cooler and stable air are expected to pick up during the evening and overnight.
DISCUSSION
... North Spain, France, South UK, Belgium, West Germany and Switzerland...
In the morning hours, elevated storms will likely be ongoing north of the warm front across and around the English Channel. These storms may pose a risk of heavy rainfall. Weaker storms and cloudiness may also be present further south, potentially affecting the situation later on and establishing some outflow boundaries, along which convective initiation could take place in the afternoon.
NWP models are in agreement that the boundary layer over the area will be humid, and that fairly steep 6.5+ K/km mid-tropospheric lapse rates will be in place. In the afternoon, MLCAPE will be in the 1500 - 2500 J/kg over large parts of France with the notable exception of western regions, overlapping with 0-6 km bulk shear in the 20-25 m/s range. The best potential for intense supercells, based on the forecast hodographs, will exist over S France and north of Massif Central.
The storm coverage will quickly increase towards the late afternoon and evening as the trough approaches from Spain and a diffuse cold front moves E-ward across the region. While isolated supercells with a (very) large hail threat are likely first, upscale growth is expected between 18 and 21 UTC with a large mescoslale convective system travelling north to northeast, capable of severe wind gusts and heavy rainfall. The storms will spread both northward and eastwardE during the night with a continuing isolated severe weather threat of heavy rainfall, large hail and severe wind gusts.
... Alps, South Germany, Czechia, Austria, Hungary, Slovakia, Poland, Romania, West Ukraine ...
This is a complicated forecast to make for the region, where the outcome of the scenario will likely depend on how far the overnight and morning storms will move and how far drier air in its wake be pushed southward.
It is likely that a cluster of storms will be ongoing over Hungary, Slovakia and/or South Poland in the morning. This cluster will continue moving eastward and may reinvigorate in the afternoon hours over Romania as MLCAPE increases in response to diurnal heating. Moderate shear will maintain cell regeneration along gust fronts and isolated severe weather is forecast here, especially heavy rainfall.
To its west, models still depict 500-1000 J/kg MLCAPE across Austria, southern Czechia and Slovakia, ahead of a front that will advance a little southward. Initiation is most likely near the front and over mountains. With straight hodographs and 0-6 km bulk shear between 15 - 25 m/s, splitting storms are forecast with isolated occurrence of large hail and severe wind gusts. The threat will be highest over the Alps and in the Alpine forelands of Austria, West Hungary, and Slovenia. A broad Lvl 1 is introduced for the whole discussed region, but note that in some areas (such as E Hungary), this reflects more the threat associated with the early morning MCS passage rather than the afternoon storms.
... Türkiye into Caucasus ...
Widespread storms capable of locally heavy rainfall and isolated large hail, are forecast over West and Central Türkiye. The storms will typically not be well-organized since the wind shear is modest, but they will be numerous and fairly powerful as a result of reasonably high CAPE. Further storms are forecast towards the Caucasus region, where CAPE is even more impressive with values exceeding 2000 J/kg even over higher terrain. This suggests a large hail threat will exist, and, courtesy of the high cloud bases, a pronounced risk of downbursts will be present as well.
... South Russia and Eastern Ukraine...
Isolated to scattered storms will form in an environment of 0-6 km bulk shear of 15 - 20 m/s and MLCAPE around 1000 J/kg. Some isolated large hail and severe wind gusts can be expected.
