Extended Forecast
Valid: Fri 07 Jun 2024 06:00 to Sat 08 Jun 2024 06:00 UTC
Issued: Wed 05 Jun 2024 21:46
Forecaster: TUSCHY

A level 2 was issued across SE Austria mainly for large hail and severe wind gusts. A very large hail event is possible.

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

A level 1 was issued for SE France mainly for large hail and severe wind gusts.

A level 1 was issued for parts of Portugal/Spain mainly for large hail and heavy rain.

A level 1 was issued for parts of Turkey and Georgia mainly for large hail and severe wind gusts.

A level 1 was issued for parts of W Russia mainly for heavy rain.

SYNOPSIS
Not much change to the SWODY 1 discussion with a more or less stationary mid/upper wave pattern. The most progressive feature will be the anomalous deep trough, which moves into SW Europe and carves out a deep W European trough pattern as it approaches the deep trough over the Norwegian Sea. Another low-amplitude wave affects SE Europe whereas otherwise rising heights start to dominate most of the Mediterranean.

Frontal wise not much regional change occurs with the extensive and wavy frontal boundary, probably not only modulated by passing short-waves but also by locally enhanced convection from the previous day.

DISCUSSION

... France to Austria ...

Another round of CI along the Massif Central is forecast beyond noon with 15-20 m/s DLS and 500-1000 J/kg MUCAPE in place. Once again, background forcing on the synoptic-scale remains diffuse, but NWP guidance remains rather bullish (including ensemble data) for scattered CI along the orography. This activity shifts E with a mixture of multicells/semi-discrete supercells. Large hail and severe wind gusts will be the main hazard next to heavy rain.

Further E in CNTRL/E Austria, another round of mountain storms occurs beyond noon, which shifts E/SE. A passing low-amplitude wave during peak heating may boost CI to scattered with modest DLS around 15 m/s and MUCAPE in the 1.5 kJ/kg range. Once again, local orography should modify shear profiles with up to 20 m/s DLS forecast and hence expect another round of SE ward shifting supercells with large to isolated very large hail and strong to severe wind gusts. Some inverted-V profiles over far SE Austria should support growing cold pools which drive an organized cluster into NE Slovenia and far W Hungary before weakening. A level 2 upgrade was performed with high confidence in expected DMC activity.


From E Slovakia into the W Ukraine and W Belarus, the nocturnal cluster from the previous night may re-intensify in this area with new CI also along its SE-ward shifting outflow. 15 m/s DLS and 500-1000 J/kg MUCAPE are enough for organized DMC acitivty, but uncertainty is high right now where to place any level 1, as the exact motion/speed of the nocturnal cluster remains diffuse in NWP guidance. For now we used the mid-level thermal gradient as the potential path of the cluster and we placed the level 1 just to the S like well into the Ukraine. However modifications of this level area are certainly possible if the final cloud/precipitation issue becomes better defined in NWP guidance. Large hail, heavy rain and a few severe wind gusts are possible with this activity.

...Portugal and W Spain ...

As an upper trough draws near from the SW, enhanced onshore flow beneath a plume of augmented mid-level lapse rates creates a broad region with 500-1000 J/kg MUCAPE - locally higher over N Portugal.

Afternoon convection occurs over N-Portugal into far NW Spain with strong to severe multicells (10 m/s DLS). Well mixed BL profiles and mentioned CAPE support a few large hail and severe downburst events.

During the late afternoon, a cold front moves inland into S Portugal and shifts N. This front sparks scattered storms well into the night. Shear remains weak to modest, so a few large hail and strong gusts are forecast but the main issue becomes heavy rain betimes with clustering convection. During the end of the forecast there will be a growing risk of an isolated supercell event over far S-CNTRL Spain but the elevated nature and modest CAPE preclude an upgrade for now.

... Turkey and Georgia ...

A few high-based storms may bring numerous severe downburst events next to isolated hail with deep inverted-V profiles.

This is valid for W and E Turkey into Georgia.

...W-Russia...

Slow moving convection becomes a heavy rain issue and a level 1 was once again placed next to a more pronounced LL convergence zone.