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: 05/09/2020 06 UTC – 06/09/2020 06 UTC
Issued by: Severe Weather Europe
Forecaster: Marko Korošec

SUMMARY

 
Severe storms with large hail, severe winds, and torrential rainfall are possible from the Alps towards Poland. Dangerous storms are possible across the eastern Black Sea into Georgia on Saturday.

Overview of the risk areas across Europe

 
weather forecast

 

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

 

SYNOPTIC OVERVIEW

 
A strong ridge develops over the North Atlantic, while a large trough strengthens over northern Europe. An associated surface front tracks east across east-central Europe. Two upper lows bring more storms over Tunisia and eastern Black Sea region.

FORECAST DISCUSSION
+++ Black Sea, Ukraine, Russia, Georgia, Turkey and Armenia +++

 
weather forecast area 1

ENH/SLGT risks have been issued for the eastern Black Sea, southeast Ukraine, southwestern Russia, Georgia, eastern Turkey, and Armenia with a threat for severe storms, capable of producing severe winds, torrential/excessive rainfall, and marginal hail.

A deepening upper low will result in a rather widespread convective activity. Slow-moving storms are likely, so excessive rainfall threat will develop, posing threat for flooding. Moderate shear and instability should also support supercell storms with large hail and severe winds threat.

+++ the Alps, Czechia, Austria, Germany, Slovakia and Poland +++

 
weather forecast area 2

SLGT risk has been issued southern Germany into most of Austria, eastern Czechia, northwestern Slovakia, and southeast Poland with a threat for isolated severe storms, capable of producing severe winds, torrential rainfall, and large hail.

A weak cold front crosses from west to east, characterized by quite strong 40-50 knots shear but only weak to moderate instability. CAPE around 1000 J/kg will likely build up. During the afternoon hours, isolated to scattered storms will develop along the front.

A few supercell storms are also possible, those could bring severe winds and large hail. Storms will gradually continue east-northeast into the evening hours. They could merge into a larger cluster with mainly severe winds and torrential rainfall threat.

+++ other areas +++

 

MRGL risk has been issued for northest Algeria into Tunisia with a threat for isolated severe storms, capable of producing severe winds, torrential rainfall, and large hail.

TSTM risks have been issued for Morocco and part of Scandinavia 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.)