Mesoscale Discussion
Valid: Sat 14 Jun 2025 08:00 to Sat 14 Jun 2025 12:00 UTC
Issued: Sat 14 Jun 2025 07:57
Forecaster: TUSCHY

A Mesoscale Discussion was issued to update the evolving severe risk over Luxembourg/S Belgium to W into NW Germany but also for far S Germany. Please keep in mind that the MD's validity won't match the expected timing for DMC activity.

As discussed in the main outlook the chance for a convectively amplified low-amplitude wave passage is increasing. Latest radar data over NE France reveals ongoing convection next to the wave and this is in line with new NWP data, which now brings an amplified PV anomaly into W/NW Germany during the afternoon. In addition, latest runs continued the trend to shift the more amplified wave on a more southerly track. This change now increases the overlap of 1500 J/kg MUCAPE with 15 to near 20 m/s DLS. The downward building PV anomaly also increases the mid-tropospheric wind field, so confidence increased in a regional setup supportive for organized multicells and a few supercells.

Initiating cells and semi-discrete cells pose a large hail threat with hail diameter in excess of 5 cm not ruled out on a local scale. Strong downdrafts increase the risk of severe downbursts, especially as convections clusters with improving cold pools and swaths of strong to temporarily severe gusts are possible. Heavy to very heavy rain is also forecast mainly with merging convection or during interaction with the orography.

Convection starts a weakening trend during the evening hours as BL stabilizes.


Another MD was added for far S Germany, where NWP guidance still offers diverging signals for CI. Latest ID2/RUC data however increases confidence that Alpine convection could spread N into an environment of 2000-3000 J/kg MUCAPE with very weak DLS (5 m/s or less). If this scenario verifies, we could see a risk of clustered severe with isolated large hail and severe downbursts. The main risk however would be excessive rain with merging and clustering convection.

No upgrade seems necessary for both areas with lingering uncertainties about CI (southern MD) and dominant storm mode (W/NW Germany). However, as stated in the main outlook, clustered severe reports are possible and a few extreme events (e.g. hail and gust) cannot be ruled out. The level 1 over S Germany may be enlarged a bit to the E however.

A level 2 upgrade (northward expansion) seems increasingly likely for S Belgium into Luxembourg for the evening and overnight hours. The more southerly track of the wave now assists in plenty of airmass recovery during the afternoon with MUCAPE in the 2000-3000 J/kg range and roughly 15 m/s DLS but also improving 0-3 km shear. The main uncertainty is how long subsiding background conditions behind the departing wave suppress CI as otherwise weak to zero capping exists around peak heating. Severe convection with all kind of hazards is now increasingly likely and a few extreme events (hail/gusts) are also forecast. A lowered LCL also adds an isolated tornado threat.