Back-to-Back Pacific Storms to Impact the West Coast; Heavy Snow in the Central Appalachians

Back-to-back powerful Pacific storm systems to impact the Pacific Northwest and northern California through the end of this week with heavy rain, flooding, strong winds, and higher elevation mountain snow. A strong, long-duration atmospheric river will accompany the Pacific storms, bringing excessive rainfall and flash flooding to southwest Oregon and northwest California through the week. Read More >

Experimental Enhanced Hazardous Weather Outlook

Product Suite Last Updated: Sunday November 28, 2021 09:05 PM

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Severe Thunderstorm Risk

Current Time - 7 AM

24 Hr. Hazards	Day 1
Severe Thunderstorm Arrival Tool
Tornado
Hail
Thunderstorm Wind Gust
Severe Thunderstorms
Lightning
Flooding
Fire Weather
Grassland Fire Weather Index
Fog
Non Thunderstorm Winds
Excessive Heat
Snow & Sleet
Ice Accumulation
Frost & Freeze
Excessive Cold

Severe Thunderstorm Arrival Tool Legend Severe Thunderstorm Safety Tips

Risk Level		Definition
	None	Severe thunderstorms are not expected today or tonight.
	Later Today or Tonight	Severe thunderstorms will be possible later today or tonight .
	Next 6 hours	Severe thunderstorms will be possible in the next 6 hours.
	Next 3 hours	Severe thunderstorms will be possible in the next 3 hours.
The Severe Thunderstorm Arrival Tool is a resource for municipalities, counties, and SKYWARN storm spotters to plan for possible storm spotter activation on the current calendar day. Other interests can also use the Severe Thunderstorm Arrival Tool to determine the expected time frame for severe thunderstorm potential.

Tornado Risk Legend Tornado Safety Tips

Risk Level		Definition
	None	No tornado risk.
	Limited	Probability of a tornado within 25 miles of a point: less than 10 percent. Be aware of where your closest interior shelter is located.
	Elevated	Probability of a tornado within 25 miles of a point: Equal to or greater than 10 percent. Be prepared to move to the closest strong interior shelter if you are in a vulnerable location: outdoors, in a motor vehicle, mobile home, or other vulnerable structure.
	Significant	Probability of a tornado within 25 miles of a point: Equal to or greater than 30 percent. Plan to move to your closest strong interior shelter if you are in a vulnerable location: outdoors, in a motor vehicle, mobile home, or other vulnerable structure.
	Extreme	Probability of a tornado within 25 miles of a point: Equal to or greater than 45 percent. Plan to move to your closest strong interior shelter if you are in a vulnerable location: outdoors, in a motor vehicle, mobile home, or other vulnerable structure.

Hail Risk Legend Severe Thunderstorm Safety Tips

Risk Level		Definition
	None	No risk of hail.
	Limited	Risk of sub-severe hail (less than 1") or Probability of severe hail (1" or greater) within 25 miles of a point: less than 15% Be aware of potential need to move vehicles, people, and animals for protection.
	Elevated	Probability of severe hail (1" or greater) within 25 miles of a point: Equal to or greater than 15% Be prepared to move vehicles, people, and animals for protection.
	Significant	Probability of severe hail (1" or greater) within 25 miles of a point: Equal to or greater than 45% Plan to move vehicles, people, and animals for protection.
	Extreme	Probability of severe hail (1" or greater) within 25 miles of a point: Equal to or greater than 60% Plan to move vehicles, people, and animals for protection.

Thunderstorm Wind Gust Risk Legend Severe Thunderstorm Safety Tips

Risk Level		Definition
	None	No thunderstorm wind risk.
	Limited	Risk for sub-severe wind gusts (less than 58 mph) or Probability of severe wind gusts (58 mph or greater) within 25 miles of a point: Less than 15% Be prepared to secure unsecured property to prevent wind damage.
	Elevated	Probability of severe wind gusts (58 mph or greater) within 25 miles of a point: Equal to or greater than 15% Be prepared to secure unsecured property to prevent wind damage. Prepare to move to an interior shelter.
	Significant	Probability of severe wind gusts (58 mph or greater) within 25 miles of a point: Equal to or greater than 45% Plan to secure unsecured property to prevent wind damage. Plan to move to an interior shelter.
	Extreme	Probability of severe wind gusts (58 mph or greater) within 25 miles of a point: Equal to or greater than 60% Plan to secure unsecured property to prevent wind damage. Plan to move to an interior shelter.

Severe Thunderstorm Legend Severe Thunderstorm Safety Tips

Risk Level		Definition Severe Thunderstorm Risk Day 2 to 7
	None	No risk of severe thunderstorms.
	Limited	Risk for severe thunderstorms with the Probability of severe thunderstorms within 25 miles of a point:* Less than 15% Review weather safety tips and emergency kit.
	Elevated	Probability of severe thunderstorms within 25 miles of a point:* Equal to or greater than 15% Review weather safety tips and emergency kit. Identify closest safe shelter.
	Significant	Probability of severe thunderstorms within 25 miles of a point:* Equal to or greater than 45% Review weather safety tips and emergency kit. Identify closest safe shelter.
	Extreme	Probability of severe thunderstorms within 25 miles of a point:* Equal to or greater than 60% Review weather safety tips and emergency kit. Identify closest safe shelter.

Lightning Legend Lightning Safety Tips

Risk Level		Definition
	None	No lightning risk
	Limited	Thunderstorms expected to be isolated to scattered in coverage. Atmospheric conditions support cloud to ground lightning strikes in and near thunderstorms. Be aware for thunderstorms in your area.
	Elevated	Thunderstorms expected to be numerous in coverage. Atmospheric conditions support cloud to ground lightning strikes in and near thunderstorms. Be prepared to take immediate shelter from thunderstorms and lightning.
	Significant	Widespread thunderstorms are expected. Atmospheric conditions support cloud to ground lightning strikes in and near thunderstorms. Plan to take immediate shelter from thunderstorms and lightning.
	Extreme	Thunderstorms are expected with nearly continuous cloud to ground lightning strikes in and near thunderstorms. Plan to stop all outdoor activity and move to shelters. Remain in shelters until all danger of wind and lightning has passed.

Flooding Legend Flooding Safety Tips

Risk Level		Definition
	None	No Flooding risk.
	Limited	Risk of localized flash flooding of small streams and low water crossings, and minor flooding of poor drainage or urban areas. Be aware of flood prone areas and potential to change your driving course if roadways flood.
	Elevated	Risk of flash flooding of several low water crossings, roads, and small streams, or Minor River Flooding. Be prepared to move away from flood prone areas. If you observe flooded roadways, be prepared to change your driving course.
	Significant	Risk of flash flooding of numerous roads, low water crossings, and small streams, or Moderate river flooding. Plan to move away from flood prone areas. If you observe flooded roadways, change your driving course or stay off roads completely.
	Extreme	Risk of widespread flash flooding of low water crossings, roads, and small streams. or Major river flooding. Plan to move away from flood prone areas. If you observe flooded roadways, change your driving course or stay off roads completely.

Fire Weather Legend Wildfire Weather Safety Tips

Risk Level

Definition

None

Open burning is usually safe with proper containers and precautions under low fire danger conditions.
Residents should always check on local ordinances that prohibit open burning under any conditions.

Limited

Open burning is usually safe with the proper precautions.
Burning should be done in the early morning and late evening to avoid windier and drier conditions from midday through mid-afternoon.
Residents should always check on local ordinances that prohibit open burning under any conditions.

Elevated

Any open burning is discouraged due to increased wind and lower humidity - except by experienced fire personnel.
Increasing winds and lower humidity contribute to drying fuels. Fires escape control more easily and containment is difficult for inexperienced fire personnel.
Approaching Red Flag conditions.

Significant

Open burning should not be attempted.
High winds and extended dry periods lead to extreme burning conditions. Open fires can quickly escape and are very difficult to control, even for experienced fire fighters.
Conditions exceed minimum criteria for a Red Flag Warning in most cases.

Extreme

Very strong winds, well in excess of Red Flag Criteria combined with moderate to low humidity.
Fires will spread very quickly with spot fires common. Fire control is extremely difficult due to very strong winds.

***These definitions are geared towards the general public and general emergency management and should not be confused with the standard National Fire Danger Rating System (NFDRS) adjectives used by wildland fire personnel.

The fire weather category for the Enhanced Hazardous Weather Outlook is based primarily on predicted wind, humidity and temperature, and does not account for fuel moisture from recent precipitation, snow cover and recently melted snow. Appropriate adjustments to the fire environment must be made.

Fire weather hazard categories will normally be more restricted, generally in the "none" or "limited" categories from May 1st to September 30th due to normally predominant green and moist live vegetation. This will be subject to change during unusual severe Spring and/or Summer drought.

Grassland Fire Weather Legend Wildfire Weather Safety Tips Grassland Fire Danger Index

Risk Level

Definition

Low-Moderate

Favorable to marginal weather conditions with moderate to high moisture content of grasses and other dry organic material on the ground, indicating that the probability of a fast moving fire is low to a slight potential. Outdoor burning under these conditions can usually be performed with reasonable safety precautions, but should be monitored. Difficulty of fire suppression: Headfire can generally be stopped by road and tracks in low conditions and with water under moderate conditions.

High

Unfavorable weather conditions and low moisture content of grasses and other dry organic material on the ground, indicating that there is a high potential for fire to spread. Outdoor burning should be restricted to early morning or evening hours when wind speeds are usually lower and the relative humidity is higher. Burning is still favorable for well-planned burns by experienced land management personnel. Difficulty of fire suppression: Headfire attack generally successful with water.

Very High

Very poor weather conditions and very low moisture content of grasses and other dry organic material on the ground, indicating that dangerous burning conditions exist. Fires will spread rapidly and show erratic behavior. Outdoor burning is not recommended other than for experienced land management personnel. Difficulty of fire suppression: Direct headfire attack will become increasingly difficult. Spot fires are more likely.

Extreme (GFDI 50-75)

Extreme weather conditions and very low moisture content of grasses and other dry organic material on the ground, indicating that critical burning conditions exist. All fires have the potential to become large and spread quickly and become erratic with extreme fire behavioral characteristics. Difficulty of fire suppression: Direct attack on a headfire will generally fail. Back burn from a secure good line with adequate manpower and equipment. Flanks may become more difficult to control in shifting or erratic winds. Spot fires are likely.

Extreme (GFDI > 75)

Extreme grassland fire weather conditions that are rarely experienced in our area. Very high winds and low humidity with very dry cured grasses. Any fire that starts will spread rapidly and almost impossible to control. Fire suppression: Direct attack will likely fail, especially in heavy fuel loads.

The Grassland Fire Danger Index (GFDI) is a numerical value that indicates the potential for grassland fires to experience extreme fire behavior. The GFDI combines the curing (%), temperature (deg C), relative humidity (%), and the average of the sustained wind and wind gust speed (km/hr).

Fog Legend Fog Safety Tips

Risk Level		Definition
	None	No risk of fog.
	Limited	Fog with visibilities less than or equal to 1 mile.
	Elevated	Fog with visibilities less than or equal to 1/2 mile.
	Significant	Fog with visibilities less than or equal to 1/4 mile.
	Extreme	Fog with near zero visibilities.

Non Thunderstorm Wind Legend Wind Safety Tips Boating Safety Tips

Risk Level		Definition
	None	Sustained winds < 20 mph and Wind gusts < 30 mph.
	Limited	Sustained winds 20-29 mph or Wind gusts 30-44 mph. Be aware that unsecured property may need to be secured from potential wind damage.
	Elevated	Sustained winds 30-39 mph or Wind gusts 45-57 mph. Be prepared to secure unsecured property from potential wind damage.
	Significant	Sustained winds 40-49 mph or Wind gusts 58-64 mph. Plan to secure unsecured property from potential wind damage and move people and animals to interior shelters
	Extreme	Sustained winds > 50 mph or Wind gusts > 65 mph. Secure unsecured property from potential wind damage and move people and animals to interior shelters.

Excessive Heat Legend Excessive Heat Safety Tips

Risk Level

Definition

None

Maximum Apparent Temperature < 95

Limited

Maximum Apparent Temperature 95 to 104
Sunstroke, muscle cramps and/or heat exhaustion possible with prolonged exposure. Be aware to stay hydrated and seek air conditioned locations if needed. Identify air conditioned locations to move to.

Elevated

Maximum Apparent Temperature 105 to 109
OR
Maximum Apparent Temperature greater than or equal to 100 for 4 consecutive days.
Sunstroke, muscle cramps and/or heat exhaustion likely with prolonged exposure. Be prepared to stay hydrated and seek air conditioned locations if needed.

Significant

Maximum Apparent Temperature 110 to 114
OR
Maximum Apparent Temperature greater than or equal to 105 for 4 consecutive days.

Sunstroke, muscle cramps and/or heat exhaustion likely with prolonged exposure. Stay hydrated and seek air conditioned locations if needed.

Extreme

Maximum Apparent Temperature greater than or equal to 115
OR
Maximum Apparent Temperataure greater than or equal to 105 for 5 consecutive days.
Sunstroke, muscle cramps and/or heat exhaustion likely. Stay hydrated and seek air conditioned locations if needed.

Note:	Apparent Temperature is defined as:
		Wind Chill Temperature during the cold season.
		Heat Index Temperature during the warm season.

Snow and Sleet Legend Winter Weather Safety Tips

Risk Level		Definition
	None	No snow or sleet.
	Limited	Snow and/or sleet with less than 1 inch of accumulation expected. Be aware of locally hazardous travel conditions on bridges, overpasses, and untreated or secondary roads.
	Elevated	Snow and/or sleet with 1 to 5.9 inches of accumulation expected. Be prepared to reduce travel speed for hazardous travel conditions especially on bridges, overpasses, untreated and secondary roads.
	Significant	Snow and/or sleet with 6 to 11.9 inches of accumulation expected. Plan for hazardous travel conditions. Avoid travel if possible.
	Extreme	Snow and/or sleet with greater than or equal to 12 inches of accumulation expected. Travel will be dangerous and may be impossible. Avoid travel unless it is an emergency.

Ice Accumulation Legend Winter Weather Safety Tips

Risk Level		Definition
	None	No freezing rain or drizzle.
	Limited	Very light freezing rain or drizzle with up to a thin glaze, OR Freezing Fog. Be aware of locally hazardous travel conditions on bridges, overpasses, and untreated or secondary roads.
	Elevated	Freezing rain or drizzle with accumulation less than 1/4 inch. Be prepared to reduce travel speed for hazardous travel conditions especially on bridges, overpasses, untreated and secondary roads.
	Significant	Freezing rain with accumulation of 1/4 inch to less than 1 inch. Plan for hazardous travel conditions. Powelines and trees may be damaged resulting in localized to scattered power outages. Avoid travel if possible and prepare for possible power outages.
	Extreme	Freezing rain with accumulation of greater than or equal to 1 inch. Travel will be dangerous and may be impossible. Powerlines and trees likely damaged resulting in widespread power outages. Avoid travel unless it is an emergency and prepare for extended power outages.

Frost and Freeze Legend

Risk Level		Definition
	None	No danger of frost or freeze causing damage to vegetation.
	Limited	Patchy frost during the growing season with minor damage to unprotected vegetation. Be aware that vegetation may need to be protected.
	Elevated	Frost expected during the growing season with damage to unprotected vegetation. This may include temperatures less than or equal to 32 degrees F for less than 3 hours. Be prepared to protect vegetation.
	Significant	*Freeze expected (less than or equal to 32 degrees F for 3 or more hours) during the growing season with significant damage to unprotected vegetation.* Protect vegetation.
	Extreme	*Hard freeze (less than or equal to 28 degrees F) during the growing season with catastrophic damage to unprotected vegetation.* Protect vegetation when watches and warnings are issued.

Excessive Cold Legend Extreme Cold Safety Tips

Risk Level

Definition

None

Minimum apparent temperature greater than or equal to 10 degrees F.

Limited

Minimum apparent temperature -9 to 9 deg F.
Frostbite and hypothermia may occur with prolonged exposure without proper clothing. Be aware to have proper clothing for exposure and limit or eliminate exposure if possible.

Elevated

Minimum apparent temperature -10 to -24 deg. F
Frostbite and hypothermia could occur within 30 minutes without proper clothing. Be prepared to have proper clothing for exposure and limit or eliminate exposure if possible.

Significant

Minimum apparent temperature -25 to -34 deg. F.
Frostbite and hypothermia will likely occur within minutes without proper clothing. Have proper clothing for exposure and limit or eliminate exposure.

Extreme

Minimum apparent temperature less than or equal to -35 degrees F
Frostbite and hypothermia will occur within minutes without proper clothing. Have proper clothing for exposure and limit or eliminate exposure.

Note:	Apparent Temperature is defined as:
		Wind Chill Temperature during the cold season.
		Heat Index Temperature during the warm season.

The Experimental Enhanced Hazardous Weather Outlook is an experimental product that will be posted to this page for evaluation. We encourage your comments or suggestions for improvements using the electronic survey provided. Your feedback will help us determine product utility, if modifications are needed, and whether the product should become part of our operational suite. | Product Description Document

The Experimental Enhanced Hazardous Weather Outlook is a decision support service that supports preparedness and response efforts prior to and during hazardous weather. This service provides decision makers with convenient access to potential weather hazard information by graphically depicting the risk of weather hazards out through seven days.

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