The Weather Risk Matrix and examples of weather situations for the five impact levels are below for you to use as a reference.
No Impactful Weather.
Do NOT use impact/likelihood table. Use NWS HeatRisk
• Small Craft Advisory
Potential threat to lives & property if no or incorrect actions are taken. Localized impacts on commerce are possible.
• Sub-advisory level snow at pass level
• Patchy road ice not associated with freezing rain
• Apparent temperatures 25-32F for elevations below 1000ft
• Apparent temperatures between -9F and 0F from the Cascade foothills to the Cascade passes
• 2" in 24 hours for elevations in urban areas
Do NOT use impact/likelihood table. Use NWS HeatRisk
*Email briefing: Include in Matrix but not in Details section
• High-end Small Craft AdvisoryCoastal Areas:
• Enhanced threat of sneaker waves
• High Surf Advisory
Potential threat to lives & property if no or incorrect actions are taken. Impacts on commerce are possible.
• Widespread road ice not associated with freezing rain
• Apparent temperatures 15-25F for elevations below 1000ft
• Apparent temperatures between -19F and -10F from the Cascade foothills to the Cascade passes
NOTE: If during growing season (Apr 1-Oct 31), add hard freeze/agricultural impacts to your email briefing details
• 0.5"/hr for 1 hour (winter) or 1.0"/hr for 1 hour (summer)
• 3" in 24 hours for elevations in urban areas
Do NOT use impact/likelihood table. Use NWS HeatRisk
• Gales and/or Hazardous Seas of 16-19 ft
• Isolated waterspouts (1 or 2 expected)Coastal Areas:
• High Surf Warning
• Coastal Flood Advisory for tidal overflow
Actions likely needed to save lives and/or property. Significant impacts to commerce possible.
• 1 to 3" of snow in urban areas below 1000 ft during the middle of a week day (impacts to commutes)
• 3 to 6" of snow in urban areas below 1000 ft overnight or on weekends
• Near blizzard conditions, but visibilities are above 1/4 mile so no Blizzard Warning is expected
• Any time apparent temperatures reach 5-15F for elevations below 1000 ft
• Long duration extreme cold (at least 3 days in a row), but not historic
• Apparent temperatures between -29F and -20F from the Cascade foothills to the Cascade passes
NOTE: If during growing season (Apr 1-Oct 31), mention hard freeze/agricultural impacts in email briefing
• 0.5"/hr for 2 hours (winter) or 1.0"/hr for 2 hours (summer)
• Debris flow criteria met, Flash Flood Watches/Warnings may be needed over burn areas
• 4" in 24 hours for urban areas
Do NOT use impact/likelihood table. Use NWS HeatRisk
• Storm Force winds and/or hazardous seas at or over 20 ft
• Freezing Spray Advisory
• Several waterspouts expected (3 or more)Coastal Areas:
• Coastal Flood Warning
Actions required to save lives and/or property. Significant and extended impacts to commerce.
• Extreme fire weather conditions and critically dry fuels warranting a Particularly Dangerous Situation (PDS) Red Flag Watch or Warning
• High-end snowstorms for elevations below 1000ft with hourly snow rates over 1"/hr during the morning and/or evening commute and snow totals around 6" or more
• Historic mountain snow amounts
• Any time apparent temperatures reach below 5F for elevations below 1000ft
• Historic long duration extreme cold event
• Apparent temperatures of -30F or colder from the Cascade foothills to the Cascade passes
NOTE: If during growing season (Apr 1-Oct 31), mention hard freeze/agricultural impacts in email briefing
• 5" in 24 hours for urban areas
• Imminent dam failure
Do NOT use impact/likelihood table. Use NWS HeatRisk
• Hurricane force winds
• Heavy freezing sprayCoastal Areas:
• Significant coastal flooding >3 ft (high-end Coastal Flood Warning)