Storm Forecast
Valid: Mon 19 Jun 2023 06:00 to Tue 20 Jun 2023 06:00 UTC
Issued: Sun 18 Jun 2023 23:41
Forecaster: PUCIK
A level 2 was issued across N Spain, W and Central France mainly for large to very large hail, severe wind gusts and excessive rainfall.
A level 1 was issued across W and N Iberia and France mainly for excessive rainfall, large hail and severe wind gusts.
A level 1 was issued across Germany mainly for severe wind gusts and large hail.
A level 1 was issued across W Alps mainly for excessive rainfall and large hail.
A level 1 was issued across the S Baltics, Belarus and Ukraine and Turkey mainly for excessive rainfall.
A level 1 was issued across Bulgaria and Romania mainly for large hail, severe wind gusts and excessive rainfall.
A level 2 was issued S of Caucasus mainly for large to very large hail and excessive precipitation.
SYNOPSIS
On a synoptic scale, the situation will remain similar compared to the previous day. A ridge over the Mediterranean and the Alpine range divides the troughs over the Atlantic and Baltics/Poland/Black Sea/Turkey. Within the SW flow of the forward flank of the Atlantic trough, two short-wave troughs are forecast. The first one will be present over Iberia at 06 UTC and cross France during the day, weakening and reaching Germany by night. The second one will move from the Atlantic over Portugal and Spain in the evening hours, reaching SW France by Tuesday morning. Towards the east, a short-wave trough will move over Lithuania, another between Romania and Bulgaria, and the other two over Turkey and the Caucasus.
Thunderstorms are forecast in the moist airmass along the wavy frontal boundary across W Europe and near the ill-defined frontal zones with enhanced moisture in the core of the trough over E Europe.
DISCUSSION
... Iberia ...
Multiple rounds of storms are likely over the area. The highest coverage is expected with the arrival of the short-wave trough from the Atlantic in the late afternoon to evening hours. A combination of multicells and supercells is forecast given 0-6 km bulk shear exceeding 15 m/s. Heavy rainfall and large hail will occur with stronger storms. Heavy rainfall threat will be most prominent over the W part of the area. Large hail and isolated severe gust risk will be present further east with higher LCLs. A lvl 2 is introduced for the area where models agree on 0-6 km shear up to 25 m/s and substantial convective precipitation. Here, expect supercells with the threat of large to very large hail and severe wind gusts.
... France ...
Elevated storms may be ongoing over the area in the warm air advection areas along the frontal boundary. Their evolution may influence the development of the afternoon storms. The highest storm coverage and intensity are expected with the arrival of the short-wave trough from Iberia. Near the convergence zone over SW France, MLCAPE > 2000 J/kg will overlap with strong deep layer shear. Towards NE, CAPE decreases, but 0-3 km shear remains favorable for multicells. First, isolated supercells may develop over SW and W France with threats of large or even very large hail. Upscale growth is likely with time, yielding a QLCS with the threat of severe wind gusts. The threat of severe wind gusts will be limited to some degree by relatively moist profiles, at least in the western part of France. Towards the east, drier airmass with higher LCLs is forecast and stronger potential for downbursts.
... Germany ...
The forecast across this area is very uncertain. Models differ quite a bit concerning the coverage of afternoon convection outside of the frontal boundary, but also in the exact positioning of the MCS that may arrive from SW during the evening and night hours. Lvl 1 is introduced in the path of the short-wave trough, which the MCS could follow as the zone of most favorable conditions for the initiation of new cells.
... S Latvia towards Ukraine ...
Scattered storms are forecast, evolving along the convergence zones. Given 0-6 km shear around or below 10 m/s, disorganized multicells are the most likely mode. A W - E moisture gradient is evident and surface observations should be monitored to forecast the most likely threat with evolving storms (rain or wind). Most storms will likely form within the moister airmass with low LCLs, yielding heavy rainfall threat the more prevalent.
... Romania to Bulgaria ...
Strong 0-6 km shear (> 20 m/s) is forecast in the rear part of the short wave that will move S across the region. Thus, expect better organization of storms compared to Sunday and also higher threat of large hail or severe wind gusts. A lvl 2 was even considered for S Romania and N Bulgaria but was not issued due to the strongest shear being situated in the region of synoptic-scale descent and models disagreeing on the convective coverage.
... Turkey and Caucasus ...
Both areas will see similar phenomena as on Sunday. Expect a predominant heavy rainfall threat over Turkey from slower moving storms. S of the Caucasus, high CAPE, and strong shear environment will allow for intense storms capable of large hail.
