Storm Forecast
Valid: Mon 28 Sep 2026 06:00 to Tue 29 Sep 2026 06:00 UTC
Issued: Sun 27 Sep 2026 14:33
Forecaster: TUSCHY

A level 1 was issued across S and NE Spain mainly for an isolated coastal tornado event and heavy rain.

A level 1 was issued for parts of Belgium/the Netherlands mainy for isolated hail.

SYNOPSIS

A blocking ridge gets framed by 2 longwave troughs to its W and E. Both bring some convective activity to W and SE Europe including a regional severe risk. In general however a rather quiet pattern for DMC activity persists.

DISCUSSION

The Alboran Sea will be placed in a brisk SW-erly mid to upper level flow regime along the periphery of a slowly eastward spreading upper trough. A temporal vortex development in the 800-700 hPa layer over SE Spain induces intense LL veering in the level 1. LL thermal stratification is neutral to slightly unstable and we probably see a mess of stratiform rain with embedded convective segments. A stronger tail-end storm is possible. In general, expect an isolated tornado and heavy rain risk with this activity as it spreads N/NE mainly during the afternoon into the evening.

During the night a plume of deep moisture (throughout most of the troposphere) hovers E of Spain. As the troposphere cools during the night, expect near uncapped 1000-1500 J/kg SBCAPE offshore with favorable kinematics for both rotating thunderstorms and temporal training along the coasts. This is valid from SE to NE Spain. Expect some local heavy rain issues with spotty 100 mm/12h not ruled out including a few tornado events (if spotted during the night). We expanded the level 1 into the orography of the Pyrenees but also towards SE Spain. Further E a cap should preclude CI.

From NW to NE France into Belgium/the Netherlands, a N-ward pushing warm front with better tropospheric moisture content offers a belt of meager to modest elevated MUCAPE. A short-wave crosses NW France during the day to SE England, which induces a somewhat augmented thunderstorm risk, which spreads from NW France to the Netherlands during the day.
Elevated CAPE and ineffective SRH probably support a few elevated rotating updrafts with ID2-EPS highlighting W Benelux to the Netherlands during the night. Small hail and heavy (but short) bursts of rain are forecast but even ensemble data has only meager gust signals. Still a low-end level 1 upgrade was performed as some concern exist for a temporal overlap during the evening into the night for robust mid-level MUCAPE with strong speed/directional shear which could support isolated hail, approaching our severe criterion.

Far W-CNTRL France into SW France could see a spotty hail risk during the night, but NWP guidance remains very scattered regarding CI and hence no level area was added.

An extensive upper trough affects SE Europe with scattered to widespread convection. Weak offshore convection is noted over the SW Black Sea, but confidence in scattered thunderstorm activity is too low for upgrading parts of NW Turkey to a rain-driven level 1, where QPFs are in the 100 mm/24h range. The Black Sea area will be monitored regarding low probabilities for subtropical development, but confidence is too low for issuing a separate bulletin.