Experimental Enhanced Hazardous Weather Outlook For Central Iowa

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.
	Elevated	Probability of a tornado within 25 miles of a point: Equal to or greater than 10 percent.
	Significant	Probability of a tornado within 25 miles of a point: Equal to or greater than 30 percent.
	Extreme	Probability of a tornado within 25 miles of a point: Equal to or greater than 45 percent.

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%
	Elevated	Probability of severe hail (1" or greater) within 25 miles of a point: Equal to or greater than 15%
	Significant	Probability of severe hail (1" or greater) within 25 miles of a point: Equal to or greater than 45%
	Extreme	Probability of severe hail (1" or greater) within 25 miles of a point: Equal to or greater than 60%

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%
	Elevated	Probability of severe wind gusts (58 mph or greater) within 25 miles of a point: Equal to or greater than 15%
	Significant	Probability of severe wind gusts (58 mph or greater) within 25 miles of a point: Equal to or greater than 45%
	Extreme	Probability of severe wind gusts (58 mph or greater) within 25 miles of a point: Equal to or greater than 60%

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%
	Elevated	Probability of severe thunderstorms within 25 miles of a point:* Equal to or greater than 15%
	Significant	Probability of severe thunderstorms within 25 miles of a point:* Equal to or greater than 45%
	Extreme	Probability of severe thunderstorms within 25 miles of a point:* Equal to or greater than 60%

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.
	Elevated	Thunderstorms expected to be numerous in coverage. Atmospheric conditions support cloud to ground lightning strikes in and near thunderstorms.
	Significant	Widespread thunderstorms are expected. Atmospheric conditions support cloud to ground lightning strikes in and near thunderstorms.
	Extreme	Thunderstorms are expected with nearly continuous cloud to ground lightning strikes in and near thunderstorms.

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.
	Elevated	Risk of flash flooding of several low water crossings, roads, and small streams, or Minor River Flooding.
	Significant	Risk of flash flooding of numerous roads, low water crossings, and small streams, or Moderate river flooding.
	Extreme	Risk of widespread flash flooding of low water crossings, roads, and small streams. or Major river flooding.

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.
	Elevated	Sustained winds 30-39 mph or Wind gusts 45-57 mph.
	Significant	Sustained winds 40-49 mph or Wind gusts 58-64 mph.
	Extreme	Sustained winds > 50 mph or Wind gusts > 65 mph.

Excessive Heat Legend Excessive Heat Safety Tips

Risk Level

Definition

None

Maximum Apparent Temperature < 95

Limited

Maximum Apparent Temperature 95 to 104

Elevated

Maximum Apparent Temperature 105 to 109
OR
Maximum Apparent Temperature greater than or equal to 100 for 4 consecutive days.

Significant

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

Extreme

Maximum Apparent Temperature greater than or equal to 115
OR
Maximum Apparent Temperataure greater than or equal to 105 for 5 consecutive days.

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.
	Elevated	Snow and/or sleet with 1 to 5.9 inches of accumulation expected.
	Significant	Snow and/or sleet with 6 to 11.9 inches of accumulation expected.
	Extreme	Snow and/or sleet with greater than or equal to 12 inches of accumulation expected.

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.
	Elevated	Freezing rain or drizzle with accumulation less than 1/4 inch.
	Significant	Freezing rain with accumulation of 1/4 inch to less than 1 inch.
	Extreme	Freezing rain with accumulation of greater than or equal to 1 inch.

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.
	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.
	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.*
	Extreme	*Hard freeze (less than or equal to 28 degrees F) during the growing season with catastrophic damage to unprotected vegetation.*

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.

Elevated

Minimum apparent temperature -10 to -24 deg. F

Significant

Minimum apparent temperature -25 to -34 deg. F.

Extreme

Minimum apparent temperature less than or equal to -35 degrees F

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

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