Mesoscale Discussion
Valid: Wed 16 Aug 2023 14:00 to Wed 16 Aug 2023 18:00 UTC
Issued: Wed 16 Aug 2023 14:31
Forecaster: TUSCHY

A mesoscale discussion was issued for parts of SW into W-CNTRL Germany mainly for an isolated large hail/severe wind gust and more widespread excessive rainfall risk well into the overnight hours (please note the MD validity is not representing the time frame for expected activity).

Latest radar composite inidcates a long-lived MCS over E France riding a SW/NE aligned CAPE axis. Some CAMS support the idea of an evolving PV+ anomaly/MCV with this feature which approaches W Germany during the overnight hours. Attendant mass response is shown by stronger LL/mid-level flow along the S fringe of this system with ongoing wide variety of intensity solutions (depending on the strength/robustness of any PV+ feature). Anyhow, this configuration of a strengthening SW-erly flow regime into the MD area increases deep mass confluence on a broader scale.

Already ongoing CI in parts of the MD will constantly increase during the evening into the overnight hours with initiating storms posing an isolated large hail/severe wind gust/heavy rain threat. Betimes, clustering convection (either incoming from France or separately evolving within the MD area) with enhanced 1-3km AGL SR winds may cause some balanced cold pool development with swaths of strong wind gusts and hail. The main risk however should be excessive rain where

- merging/clustering convection
- orography interacting with convection and potential strengthening background inflow into DMC activity
- fringes of any line-up, where SR motion of convection decreases.

PWs in the mid/upper 30s, with layered TPW anomaly up to 150%, moist conditions up to 550 hPa and deep warm cloud layers should cause effective/intense rainfall rates with an attendant flash flooding risk.

Highlighting the highest rainfall risk is not yet possible due to ongoing uncertainties like structure/path of any MCV, how progressive any line-up will be and where storm-scale process will result in flash flooding but there certainly will be a window of opportunity for a few extreme events.

During the night this activity shifts N/NE and out of this MD area with ongoing heavy rainfall issues.