What the Storm Prediction Center's Thunderstorm Outlook Means | The Weather Channel (2024)

Weather Explainers

By Jonathan Belles

March 16, 2021

What the Storm Prediction Center's Thunderstorm Outlook Means | The Weather Channel (1)

At a Glance

  • Many meteorologists use the NOAA/Storm Prediction Center severe thunderstorm outlooks for severe weather guidance.
  • These outlooks use severe risk categories, ranging from "marginal" to "high" risks.

Severe thunderstorm forecasts are issued daily by NOAA's Storm Prediction Center with threat levels ranging from "marginal risk" on the low end to the rarely used "high risk." But what do those terms mean, exactly?

The SPC, a branch of the National Weather Service located in Norman, Oklahoma,issues forecasts for thunderstorms over the next eight days.

The forecasts show areas that have a threat of severe thunderstorms and how high thethreat is, by categoriesbased on the probability that a severe weather event will occur within 25 miles of a given location.

What the Storm Prediction Center's Thunderstorm Outlook Means | The Weather Channel (2)

These forecasts are based on current trends in satellite and radar imagery, weather model output, pattern recognition, forecaster expertise and how confident the forecaster is.

According to Dr. Patrick Marsh, warning coordination meteorologist at NOAA's Storm Prediction Center, the "SPC works very hard to internally collaborate the forecast. This allows for the expertise from numerous forecasters to be conveyed in each outlook." Although one or two forecasters write a particular forecast update at the SPC, many great minds enter their thoughts into each forecast.

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

(MORE: Your Odds of Being Hit by a Tornado)

These forecast categories 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.

Lightning and flooding are just as deadly as tornadoes, large hail and damaging winds, if not moreso.

Here is a description of the thunderstorm outlook scale.

What the Storm Prediction Center's Thunderstorm Outlook Means | The Weather Channel (3)

Marginal Risk - Category 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-sized, produce gusty winds and frequent, deadly lightning.

This outlook is very common and occurs throughout the year.

Slight Risk - Category 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 one inch in diameter.

Advertisement

This outlook is common,especially in the warmer months.

Even though this outlook level is called "slight," weather that can occurin this risk area is no less deadly than the weather that occurs in a high risk. Isolated severe storms may produce significant tornadoes, very large hail and damaging winds.

If the SPC believes that the severe weather may occur from asingle thunderstorm or has a low confidence in a severe thunderstorm event occurring, then forecast probabilities and thus the category will be lowered, according to Marsh.

Enhanced Risk - Category 3

Numeroussevere thunderstorms possible.

More persistent and widespread 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.

Moderate Risk - Category 4

Widespread severe thunderstorms likely.

Most storms that form will reach the severe criterialisted above within this risk area. 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.

These risks are typically issued a few times a year.

High Risk - Category5

Widespread severe thunderstorms expected.

A severe weather outbreak is expected with multiple tornadoes and/or a destructive long-lived derecho. Damage is expected.

Tornadoes that do occur in and around this area are expected to become strong (EF2+) or violent (EF4+) 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."

Not everyone in a high-risk area will see severe weather, but the chances that communities in the high-risk area will see severe storms are generally around 30% or higher.

What the Storm Prediction Center's Thunderstorm Outlook Means | The Weather Channel (4)

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

What the Storm Prediction Center's Thunderstorm Outlook Means | The Weather Channel (2024)

FAQs

What is the meaning of thunderstorm in weather forecast? ›

Thunderstorm - A rain-bearing cloud that also produces lightning. All thunderstorms are dangerous.

What is the meaning of storm prediction center? ›

The Storm Prediction Center (SPC) at Norman, Oklahoma is a special part of the National Weather Service (NWS) charged with monitoring and forecasting severe weather over the 48 continental United States. It is presently a division of the National Centers for Environmental Prediction (NCEP).

How can forecasters predict thunderstorms? ›

Satellites take pictures of Earth at regular intervals from space, telling us where clouds are located. Meteorologists watch these pictures over time to watch for rapidly growing clouds, a clue to a possible thunderstorm.

When a severe weather watch is issued, it means select the correct answer.? ›

If a WATCH is in effect for your area, it means that conditions are favorable for the development of severe storms. You should stay alert to changing weather conditions and be prepared to take shelter if needed. If a WARNING is issued for your area, take action!

What is a thunderstorm long answer? ›

thunderstorm, a violent short-lived weather disturbance that is almost always associated with lightning, thunder, dense clouds, heavy rain or hail, and strong gusty winds.

What is the meaning behind thunderstorm? ›

thunderstorm. / thŭn′dər-stôrm′ / A storm of heavy rain accompanied by lightning, thunder, wind, and sometimes hail. Thunderstorms occur when moist air near the ground becomes heated, especially in the summer, and rises, forming cumulonimbus clouds that produce precipitation.

What does predicting the weather mean? ›

Weather forecasting is the prediction of what the atmosphere will be like in a particular place by using technology and scientific knowledge to make weather observations. In other words, it's a way of predicting things like cloud cover, rain, snow, wind speed, and temperature before they happen.

What role does the Storm Prediction Center serve? ›

The Storm Prediction Center (SPC) is part of the National Weather Service (NWS) and the National Centers for Environmental Prediction (NCEP). Our mission is to provide timely and accurate forecasts and watches for severe thunderstorms and tornadoes over the contiguous United States.

What happens at the center of a storm? ›

Air spirals in toward the center in a counter-clockwise pattern in the northern hemisphere (clockwise in the southern hemisphere) and out the top in the opposite direction. In the very center of the storm, air sinks, forming an "eye" that is mostly cloud-free. Cross section of a typical hurricane.

How do forecasters predict the weather? ›

This involves using tools such as satellites, radar, and surface maps. Meteorologists look at patterns in the atmosphere, beginning with general patterns, then narrowing it down to the more specific details. We've all heard of satellites and radar, but you might not be familiar with surface maps.

How to tell if a thunderstorm is coming? ›

Keep an eye on the sky. Pay attention to weather clues around you that may warn of imminent danger. Look for darkening skies, flashes of lightning, or increasing wind, which may be signs of an approaching thunderstorm.

Why is it so hard to predict thunderstorms? ›

Forecasting individual thunderstorm formation is a unique challenge in the meteorological world. Thunderstorms often form seemingly randomly, developing in very hard to predict places, morphing into different forms, and merging or dividing.

Should you shower during a thunderstorm? ›

It is not safe to shower during a thunderstorm. If lightning strikes a building, it may travel through water pipes and increase the risk of electrocution. To lower this risk, people should avoid all water-based activities during a thunderstorm, including bathing and washing the dishes.

Does the Storm Prediction Center issue watches? ›

When conditions become favorable for organized severe thunderstorms or tornadoes to develop, the SPC issues a Severe Thunderstorm or Tornado Watch. A tornado can occur in either type of watch, but Tornado Watches are issued when conditions are favorable for either multiple tornadoes or a single intense tornado.

How to tell if a tornado is coming? ›

An approaching cloud of debris especially at ground level, even if a funnel is not visible; A loud roar - similar to a freight train - or a strange quiet occurring within or shortly after a thunderstorm. A change in the color of the sky. Debris dropping from the sky.

What does 50% thunderstorms mean? ›

If a forecaster mentions scattered thunderstorms, this implies that 30, 40, or 50 percent of the area for which the forecast is valid is expected to experience measurable precipitation (0.01 inch or more) from thunderstorms during the valid time.

What weather happens during a thunderstorm? ›

A thunderstorm is a localized storm accompanied by lightning and thunder. It may also have gusty winds and often brings heavy rain. Some thunderstorms can also bring tornadoes and/or hail. During winter, localized heavy snow showers may also have thunder and lightning.

What does thunderstorms likely mean? ›

Likely thunderstorms: The National Weather Service uses the term “likely” to describe 60% or greater probability of measurable precipitation (0.01 inch) for a given location.

Are thunderstorms the same as rain? ›

What is a thunderstorm? A thunderstorm is a rain shower during which you hear thunder. Since thunder comes from lightning, all thunderstorms have lightning.

References

Top Articles
Latest Posts
Recommended Articles
Article information

Author: Velia Krajcik

Last Updated:

Views: 6378

Rating: 4.3 / 5 (54 voted)

Reviews: 85% of readers found this page helpful

Author information

Name: Velia Krajcik

Birthday: 1996-07-27

Address: 520 Balistreri Mount, South Armand, OR 60528

Phone: +466880739437

Job: Future Retail Associate

Hobby: Polo, Scouting, Worldbuilding, Cosplaying, Photography, Rowing, Nordic skating

Introduction: My name is Velia Krajcik, I am a handsome, clean, lucky, gleaming, magnificent, proud, glorious person who loves writing and wants to share my knowledge and understanding with you.