Storm Forecast
Valid: Fri 04 Apr 2025 06:00 to Sat 05 Apr 2025 06:00 UTC
Issued: Thu 03 Apr 2025 20:38
Forecaster: TUSCHY

A level 2 was issued across parts of S/SE Spain mainly for hail, severe gusts and a few tornadoes. A strong tornado event is possible.

A level 1 surrounds the level 2 for similar hazards with lower probabilities.

A level 1 was issued across parts of SE Turkey mainly for isolated hail and severe gusts.

A level 1 was issued across parts of N Algeria mainly for isolated hail and severe gusts.

SYNOPSIS

A stout blocking anticyclone covers most of Scandinavia and assists in a static pattern for most of Europe. An initially strong trough over far SW Europe weakens during the day but remains the main driver for organized DMC activity over parts of Spain. During the day, height falls over E Europe indicate a digging trough, but limited moisture keeps any severe risk low. The main thunderstorm activity remains confined along the Mediterranean in the vicinity of a brisk subtropical jet and modest BL moisture.

DISCUSSION

... Spain and parts of Portugal ...

A rather strong vortex just W of Portugal weakens while turning N during the day. This vortex continues to draw a plume of subtropical moisture deep into Spain. This airmass features deep moisture profiles with neutral to slighty unstable lapse rates atop. Hence a broad area of weak to moderate MUCAPE evolves during the day with peak values over far S Spain in the 400-700 J/kg range. Similar values are forecast over SE Spain during the day and affect the Valencia area during the afternoon/evening hours.

A NEward lifting trough axis becomes the main driver regarding synoptic support with an attendant upper jet, placing its left exit region over S/SE Spain during the day. Finally a weakening occlusion shifts NE deep into Spain before losing its identity thereafter. Hence a prolonged period of adequate forcing/lift exists, which should result in numerous lines/waves of DMC activity shifting to the NE during the day.

Kinematics are very favorable for organized DMC activity as forecast hodographs feature strongly curved and elongated signatures in a 20-25 m/s DLS and 20 m/s 0-3 km shear background. Some backing of the BL flow along the occlusion and attendant surface pressure trough push SRH in the 150-300 m2/s2 range for 1-3 km AGL. This parameter is enhanced over a broad area, so growing/maturing convection will have enough time to spend in a favorable CAPE/shear space. The main concern for surface based activity resides in the souther part of the level 2 where LCLs also hover around 400-500 m AGL.

Initially messy storm mode turns gradually into numerous right moving supercells betimes as they cross the level 2 area to the E/NE. Cell interaction could add some noise into the degree of longevity of supercells, but overall setup supports numerous well structured cells with all hazards possible. This includes severe gusts, hail and a few tornadoes. With that parameter space in place, a strong and long-tracked tornado event is certainly possible. Right now the highest risk resides between the Sierra Morena and Sierra Nevada.

As convection shifts N/NE during the afternoon, it outruns best CAPE/LL moisture, so it becomes a bit diffuse, how intense updrafts will be over CNTRL into E Spain. In addition, N ward moving convection also moves into a weaker shear environment.

However, we expanded the level 2 well E into the Valencia area, where thunderstorms interact with better BL moisture due to some onshore flow of marine air. CAPE shear space still supports a mix of multicells/supercells with hail (isolated large) and severe to damaging gusts due to a better mixed BL airmass. This should lower the overall tornado risk a bit although an isolated event remains still possible.
We expanded the level 2 also towards Madrid to account for some time lag of supercells losing strength despite gradually weakening shear/CAPE. All hazards including a tornado, hail and severe/damaging gusts are possible. Of interest is that some models show substantial UH tracks also in this part of the level 2.

The overall severe risk diminishes until midnight as CAPE vanishes in response to nocturnal BL cooling.

Towards S Portugal, CAPE/shear seems to be somewhat offset but still a few organized storms with gusts and hail and an isolated tornado are possible. The risk turns more to a heavy rain risk further N.

... SE Turkey ...

Onshore advecting BL moisture into steeper mid-level lapse rates causes a belt of low/moderate MUCAPE with 15 m/s DLS. 0-3 and 0-1 km shear however remain rather weak, so the main risk seems to be some hail/gusts. A low-end level was added.

... N Algeria ...

Isolated CI is forecast along the mountains with a few high based multicells/isolated supercells forecast. High LCLs and a deep mixed BL support a few strong/intense downburst events and isolated hail.