What Severe Thunderstorm Outlooks Mean For The Tornado, Wind Damage And Large Hail Threat Level

Tornado Watch Vs. A Warning: What To Know

Severe thunderstorm outlooks are issued daily by NOAA's Storm Prediction Center to convey how widespread and intense the threat of tornadoes, wind damage and large hail are on a given day. We have an in-depth look at what they mean, from a day when severe weather is expected to be isolated to a full-throttle outbreak.

A Commonly Used Tool

Many meteorologists use these outlooks to communicate a severe weather forecast to the public. You can often see them on The Weather Channel app and weather.com when severe weather threatens. They are also used by local television meteorologists and typically make the rounds on social media as well.

The forecasts show areas that have a threat of severe thunderstorms and how high the risk is. It's done by categories based on the probability that a severe weather event will occur within 25 miles of a given location.

The Storm Prediction Center issues these thunderstorm forecasts over the next eight days, with multiple daily updates in the first three days of that forecast time frame. They are based on current trends in satellite and radar imagery, weather model output, pattern recognition, forecaster expertise and how confident the forecaster is.

Level 1 To 5 Threat In Detail

Level 1 - Isolated severe thunderstorms are possible. 

• Expect strong to occasionally severe thunderstorms that are generally short-lived. These storms generally lack organization, but can still drop hail up to quarter-size, and produce gusty winds and frequent, deadly lightning.
• This outlook is very common and occurs throughout the year.
• The Storm Prediction Center calls this a marginal risk, and that's what it is referred to on The Weather Channel app and weather.com.

Level 2 - Scattered severe thunderstorms possible.

• Short-lived, isolated severe storms won't be widespread, but may still produce isolated tornadoes, spotty wind damage and hail in excess of 1 inch in diameter. That said, the intensity of the severe weather could still be significant in some cases.
• This outlook is common, especially in the warmer months.
• The Storm Prediction Center calls this a slight risk, but on the The Weather Channel app and weather.com you'll see this labeled as severe storms being "possible."

Level 3 - Numerous severe thunderstorms possible.

• More persistent and widespread severe storms are expected. Thunderstorms may produce a few tornadoes and pockets of wind and hail damage.
• Not all storms will be severe, but a few storms could be intense.
• The Storm Prediction Center calls this an enhanced risk, but on the The Weather Channel app and weather.com you'll see this labeled as severe storms being "likely."

• Most storms that form will turn severe. Several tornadoes and numerous thunderstorms containing large hail and damaging winds are likely.
• This risk is uncommon and is generally used only when supercells are capable of strong tornadoes or long-lived squall lines are expected to produce widespread damaging winds.
• You'll only see this threat level on a severe weather forecast 11 to 12 days a year, according to statistics compiled by weather.com senior digital meteorologist Jonathan Erdman.
• The Storm Prediction Center calls this a moderate risk, but on the The Weather Channel app and weather.com you'll see this labeled as severe storms being "very likely."

Level 5 - Widespread severe thunderstorms expected.

• A severe weather outbreak is expected with multiple tornadoes and/or a destructive long-lived derecho. This type of outlook is rarely issued.
• Tornadoes that do occur in and around this area are expected to become strong (EF2-plus) or violent (EF4-plus) and/or long-tracked.
• According to the SPC, "This risk is reserved for when high confidence exists in widespread coverage of severe weather with embedded instances of extreme severe."
• The Storm Prediction Center calls this a high risk, but on the The Weather Channel app and weather.com you'll see this labeled as severe storm threat being "extreme."
• Not everyone in this highest threat level will see severe weather, but the chances that communities will see severe storms are generally around 30% or higher.

(MORE: The Rarity Of High-Risk Severe Forecasts)

What The Outlooks Don't Include

Severe weather for the outlooks is defined as a thunderstorm that produces one or more of the following: measured wind gusts to at least 58 mph, storms capable of producing wind damage (trees, structures, power lines), hail at least 1 inch in diameter (the size of a quarter) and/or a tornado.

These forecast threat levels do not include the chance for excessive rainfall or flooding. Those outlooks can be found at NOAA's Weather Prediction Center.

Outlooks also do not explicitly forecast for lightning, but the risk is implied if thunderstorms are forecast.

(MORE: What Meteorologists Mean By Severe Weather)