Severe weather outlook – forecast across Europe. This forecast features areas of organized severe weather with risk levels and severe weather threats across the European continent.

SEVERE WEATHER OUTLOOK – DAY 1

 
Valid: 03/09/2020 06 UTC – 04/09/2020 06 UTC
Issued by: Severe Weather Europe
Forecaster: Marko Korošec

SUMMARY

 
Severe storms with large hail, severe winds, and torrential rainfall are possible across Romania, Moldova into Ukraine and Belarus, and from Algeria across Tunisia into southern Italy on Thursday. Severe winds are likely over northwest Scotland.

Overview of the risk areas across Europe

 
weather forecast

 

Explanations for abbreviations (TSTM, SLGT, ENH, etc.)
 

SYNOPTIC OVERVIEW

 
A deep upper low is moving across the North Atlantic, with a surface depression moving across the Faroe Islands. A weakening wave continues from central into eastern Europe, with an upper ridge building in its wake. An upper low is weakening over northern Algeria. A strong ridge persists over eastern Europe and western Russia.

FORECAST DISCUSSION
+++ Scotland +++

 
weather forecast area 1

SLGT risk has been issued for northwestern Scotland with a threat for severe winds and heavy rainfall.

A surface low travels across the Faroe Islands and pushes severe (mostly non-convective) winds across the risk area. Some gusts could reach 100 km/h near the coast of northwest Scotland, even higher over the Highlands.

+++ Algeria, Tunisia into Sicily +++

 
weather forecast area 2

SLGT risk has been issued for northern Algeria into Tunisia and Sicily with a threat for severe storms, capable of producing severe winds, torrential rainfall, and marginal hail.

Isolated storms are possible within a moderately unstable and sheared environment, associated with the weakening upper low. A few supercells will be possible, mainly with large hail and severe winds threat.

+++ Bulgaria, Romania, Moldova, Ukraine and Belarus +++

 
weather forecast area 3

SLGT risk has been issued for northern Bulgaria, east-central Romania into Moldova, central Ukraine, and eastern Belarus with a threat for severe storms, capable of producing severe winds, torrential rainfall, and marginal hail.

Scattered severe storms are again possible along with the weakening frontal system. More widespread activity seems over Romania where the better overlap of stronger shear and CAPE exists. There, a few supercells can form, with large hail and severe winds threat.

A cluster of storms is likely towards the evening hours, spreading across Romania towards the Black Sea with torrential rainfall and severe winds threat.

+++ other areas +++

 
MRGL risk has been issued for Georgia with a threat for isolated severe storms, capable of producing severe winds and marginal hail. Moderate shear and instability could support some better-organized storms.

TSTM risks have been issued for the Alps, southeast Sweden, Estonia, and the Faroe Islands with a threat for daytime driven storms. Limited shear is present, so the storms should remain sub-severe.

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Understanding Severe Weather Outlook

 

Severe Weather Outlook features areas of organized severe weather with risk levels and severe weather threats. Risk levels are divided into seven categories:

TSTM – Thunderstorms
MRGL – Marginal risk
SLGT – Slight risk
ENH – Enhanced risk
MDT – Moderate risk
HIGH – High risk
SIG – Significant risk
WNTR – Winter risk

Risk categories stand for the coverage and intensity of organized severe weather. Those could include supercells, squall lines, mesoscale convective systems, wind storms, flooding, snowstorms, or ice storms.

Severe weather threats include:

 

  • large hail (of at least 2 cm in diameter)
  • Tornadoes (including waterspouts)
  • Wind gusts (convective or non-convective) above 25 m/s (or above 90 km/h)
  • Torrential convective precipitation / Flash floods
  • Excessive rainfall (100 mm within 12 hours) / snowfall (50 cm within 12 hours)
Extremely severe weather threats include:

 

  • Large hail (of at least 5 cm in diameter)
  • Tornadoes of F2 intensity or stronger
  • Wind gusts (convective or non-convective) above 33 m/s (or above 119 km/h) or 12 Bft
  • Torrential convective precipitation / Flash floods
  • Excessive rainfall (150 mm within 12 hours or above ) / snowfall (above 100 cm within 24 hours)

Categories in the forecast represent the chance of severe weather occurring within a 40 km radius from a location. The used level is based on the conversion table of probabilistic risk into the outlook categories. A threat level is upgraded into a higher category if probabilities meet the threshold criteria for the specific threat (e.g. tornado, wind, hail, or rainfall threat).

Each individual threat area includes a detailed forecast map and discussion on the potential of severe weather threats.

Read more: Explanations for abbreviations (TSTM, SLGT, ENH, etc.)