Mesoscale Discussion
Valid: Sat 27 Apr 2024 08:00 to Sat 27 Apr 2024 11:00 UTC
Issued: Sat 27 Apr 2024 07:56
Forecaster: TUSCHY

A Mesoscale Discussion was issued for S-CNTRL France for organized convection with a flash flood risk.

Time-frame for organized convection: 22Z-06Z (and ongoing)

The main focus regarding severe convection arises along the E-bound moving cold front but also ahead of this front during the overnight hours. A pronounced 20-25 m/s prefrontal southerly LLJ impinges along the S foothills of the Massif Central and is placed beneath the exit region of a modest mid-level jet maximum, which approaches from E Spain during that time-frame. Anomalous moist prefrontal conditions are highlighted in the EFI water vapour flux parameter (also fueled by anomalous warm SSTs) and are also visible in forecast soundings from this area. Several hundred J/kg MUCAPE should prove adequate for slow moving convection. Back-building on a local scale is certainly possible with enhanced flash flooding and rainfall up to 100 l/qm in just a few hours. Would like to see more robust CAPE for higher QPF values. However, a substantial slow-down of the cold front (probably stalling in this area) assists in more training convection beyond the 06Z time-frame, so an ever increasing flash flood risk extends beyond that time-frame.