Extended Forecast
Valid: Fri 11 Apr 2025 06:00 to Sat 12 Apr 2025 06:00 UTC
Issued: Wed 09 Apr 2025 19:47
Forecaster: TUSCHY

A level 1 was issued across parts of Portugal and Spain mainly for isolated hail and strong to severe gusts. An isolated tornado risk exists.

Towards CNTRL Portugal the more dominant risk becomes heavy rain on an isolated scale.

SYNOPSIS

Ongoing rather static pattern features a stout ridge from Algeria towards the UK/Ireland, which gets framed by an extensive upper low W of Morocco and an extensive Rossby-wave, which runs from W Russia S towards Egypt. This pattern assists in deep influx of a dry/cold continental airmass over most of E Europe, stable conditions towards CNTRL Europe and an increasingly unstable setup for SW Europe. Numerous surface fronts frame the ridge but remain displaced from the best BL moisture.

DISCUSSION

... Portugal and parts of Spain ...

Downstream of a vertically stacked vortex W of Morocco/Portugal, a fetch of subtropical air gets drawn towards the Iberian Peninsula and mixes a bit with a N-ward advecting EML from Morocco/Algeria. The overlap won't be impressive but adequate for some diurnal driven MUCAPE build-up over S/CNTRL Portugal and SW Spain. NWP guidance agrees well with this scenario although mid-level lapse rates from ICON come in a tad weaker than IFS/GFS which impacts final CAPE magnitude.

A cyclonic SW-erly flow regime affects the area during the day and embedded low-amplitude waves add some temporal enhanced background QG forcing, although latest data hints at a lull around noon. The airmass becomes virtually uncapped towards Portugal with ongoing slight CIN issues further E towards S-CNTRL Spain.

CAPE/shear space features modest MUCAPE (300-700 J/kg) everywhere with increasing shear from W to E.

Clustering multicells bring some heavy rain and graupel/isolated hail to S Portugal during the day. Slightly improving DLS to 15 m/s during the afternoon also adds a low-end tornado threat mainly to S-Portugal, where LCLs remain rather low. The activity spreads N but weakens betimes as we move into the evening hours with a more stable BL. The risk keeps going over far S Portugal, where best BL moisture offsets rather weak mid-level lapse rates, offering some overnight MUCAPE.
With collapsing shear and storm motion vectors around 5 m/s, heavy rain becomes the dominant issue towards CNTRL Portugal during the night. We added a level 1 to the S part of Portugal for an isolated severe risk and upgraded also parts of CNTRL Portugal for the overnight rainfall threat (mainly driven by IFS/ICON). The latter level area however is an uncertain/marginal one for now and remains displaced from the highest soil moisture anomalies and precipitation amounts from the past weeks.

Further E towards SW/S-CNTRL Spain, kinematics improve substantially. IFS/GFS both indicate a weak inversion in the H7-H75 hPa layer, which could turn onshore moving convection more elevated betimes. In addition, CI seems suppressed a bit towards noon with NWP spread thereafter. Right now we issued a broad level 1 along the corridor of best CAPE/shear overlap in an uncapped airmass. Multicells and a few supercells are forecast with some hail/gust and an isolated tornado with the main focus from Sevilla/Cordoba N to Caceres and potentially into the Madrid area. Some point-source forecast soundings within this sector feature long hodograph signatures with lots of LL SR inflow into potentially deviating storms. This setup has to be monitored closely regarding final CAPE magnitude/CIN strength in further model updates as not much modification is needed for a rather healthy CAPE/shear space.
The level 1 was expanded well E to account for more elevated thunderstorms with some hail risk.

... Other lightning areas ...

A few areas with thunderstorm activity are forecast. This convection should stay sub-severe however. A rather broad high prob. lightning area was added for the Bay of Biscay. This accounts for an NW ward sliding upper low, which could spark a few storms on the regional scale. Ongoing cross-track spread of IFS/GFS keeps this lightning area rather broad for now.