Storm Forecast
Valid: Tue 24 Jun 2025 06:00 to Wed 25 Jun 2025 06:00 UTC
Issued: Mon 23 Jun 2025 12:03
Forecaster: TUSCHY

A level 2 was issued for parts of N-CNTRL Spain and SW France for large to very large hail and severe downbursts.

A level 1 surrounds the 2 mainly for large hail and severe gusts. Local heavy rain is possible.

A level 1 was issued for parts of the Baltic States mainly for an isolated tornado and gust threat.

A level 1 was issued from NE Romania into the Ukraine mainly for some hail, strong to severe gusts and heavy rain.

SYNOPSIS

A brisk westerly/zonal flow regime persists over most of CNTRL Europe, as an anomalous strong upper jet covers most of Denmark/Germany all the way to the Ukraine. This high index pattern gets maintained by low geopotential heights over Scandinavia into Russia with positive anomalies over S-CNTRL Europe.
A cut-off just W of Portugal starts to lift NE into Portugal and far NW Spain. Mid-upper level moisture from the African ITCZ advects into this vortex and assists in a rather moist WCB which otherwise would see more issues with mid-level drying. This system will be the main focus for DMC activity.

For the rest of Europe a modified/drier BL airmass remains displaced from any EML, so not much thunderstorm activity is forecast. Numerous synoptic-scale fronts in the polar front jet pass NW to CNTRL into E Europe but won't see any interaction with more substantial CAPE.


DISCUSSION

... N Spain into SW France ...

The day starts with a quasi-stationary WCB along a meridionally aligned cold front, which shifts leisurely E during the forecast. A moist and unstable inflow into the WCB assists in some capped MUCAPE and scattered elevated thunderstorms occur along its periphery. Augmented mid-level lapse rates atop a moist lower troposphere cause capped MUCAPE in the 1000 J/kg range, which could support an isolated hail report. Otherwise heavy rain on a local scale will be the main hazard.

The main focus for strong to severe convection arises over N-CNTRL Spain into far SW France although lingering CIN remains an issue and lowers confidence in how effective shear will be. In addition, we see a constant inflow of rather dry air from the W-Mediterranean, where subsiding air beneath the persistent anticyclone creates a rather dry airmass. Hence not much BL moisture modification is forecast.

The main focus for near surface based CI occurs near and E of Bilbao with some influx of a marine airmass from the SE Bay of Biscay (3-4 K positive SST anomaly). This moisture also spreads into SW France.
As an African EML (reenforced by the Spanish orography) spreads N and atop the high quality BL moisture (with BL mixing ratios up to 14 g/kg) abundant MUCAPE evolves with peaks in the 1500-2500 J/kg range over N-Spain, increasing to 3000-4500 J/kg towards SW France.

Persistent WAA affects the highlighted area and synoptic-scale lift improves during the afternoon, as the cut-off approaches from the SW. A gradual increase in CI occurs during the afternoon into the evening and scattered thunderstorms are forecast.

Severity of this activity depends on how deep cap will be, but despite this uncertainty, we expect deep and very unstable vertical profiles with not much entrainment forecast (e.g. due to the advection of the mentioned mid/upper level moisture from the S). Any growing updraft will see effective shear in the 10-15 m/s range, which is adequate for well organized multicells and a few supercells. Large to very large hail and severe downburst events are forecast with any longer-lived cell. In case of local clustering, growing/deepening cold pools could produce swaths of strong to severe gusts despite the rather stable low-tropospheric layer. This activity spreads N into the Bay of Biscay and W France during the night but outruns best CAPE betimes. Hence a gradual weakening trend occurs.

A local level 2 was addded, where confidence in near surface based activity is the highest.

... Baltic States ...

A vigorous depression moves from the Baltic Sea NE towards Finland and into far WN Russia. A strong 20-25 m/s low/mid tropospheric wind field overspreads an airmass with modest BL moisture content and weak mid-level lapse rates. Temporal diabatic heating pushes MUCAPE in the 200-400 J/kg range, enough for numerous low-topped showers and a few thunderstorms. LCLs below 500 m AGL and strong effective SRH rich inflow support an isolated tornado and enhanced gust risk with peak activity during the afternoon into the evening.

... NE Romania to Moldova into the Ukraine ...

A progressive cold front works its way to the SE and activates a warm sector, which offers 500-1000 J/kg MUCAPE and 20-25 m/s DLS. Scattered thunderstorms push SE and will be accompanied by hail, strong gusts and instances of heavy rain. This activity weakens beyond sunset.