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Scale of threat levels

for South Central and Southeast Wisconsin

Expression of "Likelihood"

Very High Likelihood
36% or greater
High Likelihood
26% to 35%
Moderate Likelihood
16% to 25%
Low Likelihood
6% to 15%
Very Low Likelihood
2% to 5%

Determining "Likelihood"

Likelihood = A x B

Confidence Factor

A-Value

Percent - Occurrence of hazard within a defined area

Slight
.1 or .2
10% to 20% confidence of occurrence
Slight to Medium
.3 or .4
30% to 40% confidence of occurrence
Medium
.5
50% confidence of occurrence
Medium to High
.6 or .7
60% or 70% confidence of occurrence
High
.8 or .9
80% or 90% confidence of occurrence
Coverage Factor
B-Value
Percent - Distribution of observations and/or reports within a defined area
Isolated
.1 or .2
across 10% to 20% of defined area
Isolated to Scattered
.3 or .4
across 30% to 40% of defined area
Scattered
.5
across 50% of defined area
Scattered to Widespread
.6 or .7
across 60% to 70% of defined area
Widespread
.8 or .9
across 80% to 90% of defined area

  • NOAA's National Weather Service
  • Milwaukee/Sullivan, WI Weather Forecast Office
  • N3533 Hardscrabble Road
  • Dousman, WI 53118
  • 414-744-8000
  • Page Author: MKX Webmaster
  • Web Master's E-mail: w-mkx.webmaster@noaa.gov
  • Page last modified: 2-Nov-2005 10:23 PM UTC
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