A level 1 was issued for southern Portugal mainly for tornadoes and excessive rain.
A strong mid-level jet streak curves around the cut-of low and affect the Iberian Peninsula during the period. Strong synoptic forcing can be expected at the cyclonically-sheared flank of this jet streak. This is associated with ageostrophic winds, so that the cold air over western Iberia will not spread eastward during the day. Strong diurnal heating over eastern Iberia will therefore lead to a well-mixed and hot boundary-layer that may spread westward as an EML. While the boundary-layer moisture will be mixed out over eastern Spain, remaining moisture farther west will likely favour some CAPE.
Current scenario is that intense precipitation will enter Portugal along a cold front in the morning hours. Embedded thunderstorms are expected in the moist maritime air mass. Later in the day, additional thunderstorms are forecast to develop over Spain ahead of the cold front that may cluster later on. Given the strong vertical wind shear, storms will likely organize, and supercells and bowing lines are expected to produce large hail and severe wind gusts. Additionally, tornadoes are forecast along the western and southern coasts, where low-level vertical wind shear is forecast to be strongest. Later in the period, low-level vertical wind shear is expected to increase over central Spain as well. A broad overlap of strong low-level vertical wind shear (10 m/s 0-1km bulk shear) over southern Spain as forecast by latest GFS model indicates an increasing threat of tornadic supercells in the evening hours. Especially isolated supercells may produce tornadoes, some of them may be strong.
During the night hours, the convective activity is forecast to spread eastward. Although the boundary-layer cools and instability decreases, strong vertical wind shear and forcing is forecast favour severe storms, capable of producing large hail, severe winds, and tornadoes.