Storm Forecast
Valid: Fri 23 May 2025 06:00 to Sat 24 May 2025 06:00 UTC
Issued: Thu 22 May 2025 10:19
Forecaster: TUSCHY

A level 2 was issued across parts of the CNTRL Adriatic Sea for all kind of hazards including hail, severe wind gusts, heavy rain and tornadoes.

A level 2 was issued for parts of NE Bosnia and Herzegovina/N Serbia into NW Romania mainly for severe gusts and large to very large hail.

A level 2 was issued for SE Romania into far NE Bulgaria mainly for large to very large hail, severe gusts and heavy rain.

Both level 2 areas get framed by a broad level 1 area with similar hazards but lowered probabilities.

A level 1 was issued for Berlarus N into far NW Russia mainly for a tornado, hail, gust and rain threat.

SYNOPSIS

Despite a gradual breakdown of the blocking ridge W of Europe, not many changes occur for this forecast period. A more or less stationary cyclonic vortex over Scandinavia advects a cool and (comparable) more stable airmass S. A progressive low-amplitude wave exits the N Adriatic Sea during the start of the forecast and shifts rapidly E/NE. Lowering geopotential heights affect SW Europe with another blocking ridge stretching from the far E Mediterranean N towards Russia.

Along the E fringe of that extensive upper trough a wavy front shifts gradually E/SE with an unstable prefrontal airmass serving as main focus for DMC activity over parts of E-CNTRL to SE Europe.

DISCUSSION

... CNTRL Adriatic Sea into Romania and Bulgaria ...

During the passage of the progressive low-amplitude wave, the wind field at mid to upper levels ramps up and partially overspreads the expanding CAPE plume.

From 06Z onwards the main focus exists over the CNTRL Adriatic Sea, where a basal 45-65 kt mid/upper-level jet overspreads a plume of 600-1200 J/kg MUCAPE, pushing DLS in the 20-25 m/s and 0-3 km shear in the 10-15 m/s range. Ongoing issues with the wave's geometry still add some uncertainties with the peak magnitude of the shear with ICON staying on the less aggressive side.

Ongoing storms from the previous night shift E and a mix of multicells and a few more discrete supercells pose an all-hazard threat with hail, severe gusts, heavy rain and a few tornadoes. Forecast SR hodographs indicate a good cance for longer tracked supercells in case of a due E storm motion (deviating motion).
The most organized severe risk abates during the afternoon as the wave exits E. However a lingering more isolated supercell risk exists well into the overnight hours.

The focus then shifts E towards NE Bosnia and Herzegovina into parts of Serbia and W Romania. A similar shear background affects MUCAPE in the 1000-1500 J/kg range and the setup seems supportive for a long tracked and severe bow echo with swaths of severe gusts and isolated large hail. LCLs in the 700-1000 m AGL hamper the overall tornado risk but merging cells during CI may support an isolated event (e.g. with orographic support). We expanded this level 2 far E into W Romania before a gradual weakening trend occurs during the evening hours.

A third level 2 area was added for SE Romania into far NE Bulgaria. We expect diurnal CI along the orography (noon into the afternoon hours). Attendant rain cooled air spreads off the mountainous areas and into the lowlands. There, enhanced LL convergence sparks numerous severe semi-discrete cells (mix of multicells and supercells) as DLS increases to 15 m/s with MUCAPE aoa 1500 J/kg. CI will be rather late, like late afternoon into the evening. Vertical wind profiles support rotating updrafts and broading mid-level CAPE profiles atop weak LL shear seem supportive for large / very large hail next to severe downdraft gusts and heay rain. Storms riding the onshore moving sea breeze front may be the main focus for an isolated tornado event.

... Far E Baltic States into NW Russia ...

A belt of a weakly capped prefrontal airmass with MUCAPE up to 500 J/kg meets 10 m/s shear at 3 and 6km layers. Some regionally enhanced LL shear and modest LCL heights point to an isolated tornado risk next to hail and heavy rain due to clustering/slow moving cells. The risk diminishes during the evening hours.