SPC Wx Outlooks

What the Storm Prediction Center’s Severe Weather Outlooks Really Mean

When weather forecasters talk about severe weather ahead of time, they use a system developed by the Storm Prediction Center (SPC) to show the risk of dangerous thunderstorms. The SPC’s outlooks help you understand how likely severe storms are and how serious they might become. These outlooks are not a forecast of exact weather at your house — they show risk over a region.

The outlook uses five main categories:

🟢 1. Marginal Risk (Level 1)

A Marginal risk means that isolated severe storms are possible. Most thunderstorms will be ordinary, but a few could produce strong wind gusts, small hail, or even a brief tornado. Think of this as a “keep an eye on the sky” category — you should be aware, but it’s not a strong alert.

🟡 2. Slight Risk (Level 2)

A Slight risk means forecasters have greater confidence that some storms will become severe. This doesn’t mean all storms will be dangerous, but the chance of damaging wind, hail, or a tornado is higher than in a Marginal risk. These days can still be scattered — impacts might be isolated — but preparation is important.

🟠 3. Enhanced Risk (Level 3)

An Enhanced risk indicates that severe thunderstorms are likely in several spots. These storms could be stronger and more frequent than in the Slight category. This is a step up in risk: damage from wind or hail becomes more likely, and tornado chances increase.

🔴 4. Moderate Risk (Level 4)

A Moderate risk means a significant severe weather event is expected. This category is used when there is high confidence that damaging winds, large hail, or tornadoes will occur. These events are more widespread and more dangerous. If you see this level, you should be paying close attention to watches and warnings.

🟣 5. High Risk (Level 5)

A High risk is rare — and it means forecasters believe a major severe weather outbreak is likely. Many thunderstorms with severe wind, very large hail, and strong tornadoes are expected across the risk area. High risk days are serious and usually prompt strong readiness actions in advance.

How to Read the Percentages

Sometimes you’ll see tornado risk shown as a percentage on SPC maps. These numbers tell you the chance of a tornado happening within 25 miles of any point in the outlined area.

For example, a 10% tornado risk means there’s a 10% chance that a tornado will occur within 25 miles of your location during the forecast period. That may sound small — but on most days the tornado chance is near zero. A two-digit percentage shows a meaningful risk and deserves attention.

What Is a “Hatched” Risk Area?

You may also notice some SPC maps include a hatched area — that means forecasters think stronger tornadoes (EF2 or greater) could occur in that zone.

• Hatched shading = increased risk for significant tornadoes (not just any tornado, but stronger ones).

• This does not guarantee one will happen, but it raises the level of concern.

Why These Outlooks Matter

SPC Convective Outlooks are tools to help emergency managers, weather partners, and the public prepare before severe storms begin. They describe the environmental risk — not exactly what will happen, but what could happen based on atmospheric conditions.

Understanding these risk levels helps you choose the right level of readiness: knowing when to follow updates, when to be weather aware, and when to take protective action.

Stay safe, stay informed, and always follow your local National Weather Service (NWS) office for watches and warnings.