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: 01/08/2020 06 UTC – 02/08/2020 06 UTC
Issued by: Severe Weather Europe
Forecaster: Marko Korošec
SUMMARY
Organized severe storms with threat for severe winds, large hail and torrential rainfall are possible across parts of western Europe. Another area of organized storms is in southwestern Russia.
Overview of the risk areas across Europe
SYNOPTIC OVERVIEW
An Omega blocking pattern over the European continent is gradually weakening on Saturday. A large trough over the North Atlantic continues east towards western Europe. A surface front is extending across the North Sea, Benelux, and France by midday, moving east. Another large trough is sitting over western Russia. A shallow frontal boundary extending from southwest Russia across the Black Sea, moving towards Georgia.
FORECAST DISCUSSION
+++ France, Switzerland and Germany +++
SLGT risk has been issued for E France into WNW Germany and N Switzerland with threat for severe storms, capable of producing severe winds, large hail and torrential rainfall.
Isolated to scattered organized storms are expected to develop by mid-afternoon hours along the surface front from eastern France into western Germany. Storms will spread east-northeast with the moving front through the afternoon and evening hours.
A moderately unstable and sheared environment is present in the forecast area, conducive for rotating storms to develop. A few supercells with large hail and severe winds are possible. Flash floods could develop.
Storms could cluster in the evening over Germany with mainly severe winds and torrential rainfall threat.
+++ southwest Russia and Georgia +++
SLGT risk has been issued for southwestern Russia into northwestern Georgia with threat for severe storms, capable of producing severe winds, large hail and torrential rainfall.
Although a deep-layer shear is quite strong, relatively low instability limits strongly organized storms.
MRGL risk has been issued around the SLGT risk area, covering southwest Russia, the coast of eastern Black Sea and northern Georgia. A threat for isolated severe storms with severe winds, large hail, and torrential rainfall exists.
+++ other areas +++
MRGL risk areas have been placed across the southern Balkan peninsula and inland Italy with isolated threat for severe weather with diurnal driven storms. Those will be capable of producing strong winds, marginally large hail, and torrential rainfall given their slow-moving nature.
TSTM risk areas have been placed where convective storms are likely to occur but 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 – Thundestorms
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 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.)