Storm Forecast
Valid: Thu 29 Jun 2023 06:00 to Fri 30 Jun 2023 06:00 UTC
Issued: Thu 29 Jun 2023 02:22
Forecaster: VAN DER VELDE

A level 2 was issued across northeastern Spain for large hail and severe wind gusts.

A level 1 was issued across northeastern Spain for excessive rainfall and large hail.

A level 1 was issued across southeastern France for excessive rainfall.

DISCUSSION

An upper level trough and cold front pushes eastward into western Europe, creating slightly unstable conditions from Norway south to Belgium, France and Spain. A strong shortwave trough is coming in across northern Spain with the timing coinciding with a late afternoon/evening peak in CAPE across the Ebro Valley. Southeastern France also should see enhanced storm activity. The other active area is a large low pressure system over western Russia with unstable airmass around it, and a cold front pushing from Ukraine eastward into southern Russia.

...northeastern Spain...

The initial afternoon convection will develop on the south flank of the Pyrenees and over the Sistema Iberico where the cap is weakened first. As the shortwave trough arrives during early evening over Aragon, convective initiation can be widespread and move eastward with over 1000 J/kg CAPE and mixing ratio increased along the Catalonia coast. A moderate 15 m/s deep layer shear spans the level 1 area at 18Z, while values of 25 m/s with SREH >250 m2/s2 are found over the western/southern Ebro Valley. Several supercell storms should develop which could produce very large hail and severe wind gusts in the level 2 region, but generally large hail can occur in the level 1 area as well, especially at the south flank of the Pyrenees. A local excessive rain chance exists and storm are expected to cluster into an MCS into the night and move into the NW Mediterranean Sea, helped by strong dynamic forcing under the right entrance of the 40 m/s 250 hPa jet streak over S France.

...southeastern France...

Generally weak shear and slow-moving convection with upslope flow at the west side of the Alps and parts of Massif Central can result in local excessive rainfall amounts.