Storm Forecast
Valid: Sun 29 May 2022 07:00 to Mon 30 May 2022 06:00 UTC
Issued: Sun 29 May 2022 07:02
Forecaster: PUCIK
A level 3 was issued across Bulgaria and S Romania mainly for large to very large hail, strong tornadoes and damaging wind gusts.
A level 2 was issued across Northern Macedonia, Bulgaria and Romania mainly for large to very large hail, severe wind gusts and tornadoes.
A level 1 was issued for Bosnia, Montenegro, Albania and Greece mainly for large hail and excessive rainfall.
A level 1 was issued for Italy mainly for large hail and severe wind gusts.
A level 1 was issued for E Spain mainly for large hail and severe wind gusts.
A level 1 was issued for S Finland and N Russia mainly for excessive rainfall.
A level 1 was issued for Turkey for severe wind gusts.
SYNOPSIS
A complex synoptic-scale pattern can be found over Europe with a triade of lows in the mid to upper troposphere over the northern half of Europe. A jet stream surrounds this pool of low geopotentials, especially at its southern flank. To the south of this pool, another trough is located over the Ionian Sea. The trough will move over the Balkans during the forecast period. A forward flank of this trough, along with an associated frontal boundary, will become a focus for the most severe weather potential during the forecast period.
DISCUSSION
... Northern Greece to Moldova ...
***Severe weather outbreak is possible today over parts of Bulgaria and Romania, including potential for very large hail, damaging wind gusts, and strong tornadoes***
As of 06 UTC, elevated thunderstorms have formed to the northwest of the wavy frontal boundary over Serbia and S/SW Romania. These storms may be capable of large hail as they move N. Surface observations show the frontal boundary running from North Macedonia through W Bulgaria and extreme S Romania with dewpoints up to 18 deg C. Widespread low-level clouds are covering N Bulgaria and S Romania, while cirrus cloud cover is quickly clearing from S.
It is forecast that the frontal boundary will lift N during the day and cloud clearing is likely especially over N Bulgaria and extreme S Romania. North of the warm part of the boundary, further elevated storms will likely form, posing a risk of large to very large hail in strong vertical wind shear. Along and S of the boundary, a plume of 7+ K/km mid-tropospheric lapse rates will have advected over the moist boundary layer, resulting in MLCAPE locally exceeding 2000 J/kg. Synoptic-scale lift from the upper-level trough and mesoscale lift from the frontal boundary and orography will yield scattered to widespread storms over the area, especially towards the afternoon and evening hours. At the same time, the lower tropospheric wind field will strengthen with cyclogenesis over N Bulgaria and S Romania.
Given the combination of high CAPE and strong vertical wind shear (0-3 km bulk shear > 20 m/s, 0-3 km SRH > 300 m2/s2), any storm that forms over N Bulgaria and S Romania will bear the risk of (extremely) severe weather. The highest risk of very large hail would be confined to more isolated storms (supercells). The highest risk of tornadoes is forecast with supercells crossing the warm front in an environment of low LCLs and 0-1 km SRH > 200 m2/s2. The highest risk of severe wind gusts will exist along the cold front part, where widespread initiation may congeal the storms into one or more linear segments, possibly forming a bow-echo.
Compared to ICON and GFS, ECMWF lifts the warm front more to the N/NW, which would put the corridor of the highest risk more into SW and central Romania. The current indication of Lvl 3 more reflects the GFS and ICON scenario. Most severe weather is expected between 12 and 18 UTC. Afterward, strong capping will develop along with the warm sector and storms will then only form in the elevated form on the cool side of the frontal boundary, spreading into NW Romania and Moldova. The storms will still bear the risk of large hail, excessive rainfall, and possibly even of an isolated severe wind gust.
... Italy ...
Isolated to scattered storms are forecast to develop along the mountains. Given MLCAPE > 1000 J/kg and 0-6 km bulk shear between 10 and 15 m/s, some of the storms may become severe with the threat of isolated large hail and severe wind gusts. The coverage of storms will be limited by the dry mid-troposphere, which may hamper initiation at some locations.
... SW Germany ...
Strong 0-6 km bulk shear (> 20 m/s) will overspread marginal CAPE. That said, forecast Skew-Ts and hodographs show that the CAPE is very skinny and that much of the shear in the troposphere is confined near and above the storm tops. These two factors will limit the potential for storms to become large hail-producing supercells.
... E Spain ...
While the coverage of storms may remain low with no apparent forcing except for local topography, an environment characterized by MLCAPE around 1000 J/kg, high LCLs, and moderate shear may support large hail and severe wind gust production in any storm that forms.
... S Finland to Russia ...
Slow-moving storms are forecast to develop over the area. Skinny CAPE profiles with most of the CAPE confined to the warm part of the cloud, combined with low LCLs, suggest that some of the storms may locally produce very heavy rainfall.
... W Turkey ...
Isolated to scattered storms may form over the area in the environment of MLCAPE around 500 J/kg, high LCLs and steep lower tropospheric lapse rates. This suggests potential downburst threat with any storm that forms, warranting a Lvl 1.
