SPC Convective Outlooks: Days 1–8
Detailed forecasts for severe and general thunderstorm threats across the continental United States.
Days 1, 2, and 3 Outlook (Categorical & Probabilistic)
The Day 1, 2, and 3 outlooks contain both graphical categorical risk and graphical probabilistic risk information.
Graphical Categorical Risk
The categorical graphic uses numbers, words, and colors to depict the risk based on the coverage and intensity of organized severe weather (supercells, squall lines, and multicell thunderstorm complexes). Pulse-type thunderstorms, which consist primarily of solitary brief severe updrafts (often in weakly sheared environments), are not considered organized for this purpose.
| Category | Color | Frequency (Average yearly frequency at or above each category) | Description of Risk |
|---|---|---|---|
| Thunderstorms | Light Green | ~350-355 days per year | Encloses a 10% or higher probability of thunderstorms. |
| 1 (Marginal) | Dark Green | ~270-280 days per year | Includes severe storms of either limited organization and longevity or very low coverage. |
| 2 (Slight) | Yellow | ~200 days per year | Implies organized severe thunderstorms are expected, but usually in low coverage with varying levels of intensity. |
| 3 (Enhanced) | Orange | ~80-85 days per year | Depicts a greater concentration of organized severe thunderstorms with varying levels of intensity. |
| 4 (Moderate) | Red | ~14 days per year | Indicates potential for widespread severe weather with several tornadoes and/or numerous severe thunderstorms, some of which may be intense. |
| 5 (High) | Magenta | 2-3 days per year | Suggests a severe weather outbreak is expected from either numerous intense to violent long-track tornadoes or a long-lived derecho system with hurricane-force wind gusts producing widespread damage. |
Graphical Probabilistic Risk
Coverage
- Definition: The probability values represent the chance of severe weather occurring within 25 miles of any point, which is approximately the size of a major metropolitan area.
- Day 1 & 2: The outlook contains individual severe probabilities for tornadoes, wind, and hail.
- Day 3: Due to greater uncertainty, the outlook only forecasts the combined probability of all three types of severe weather.
- Context: Probabilities for severe thunderstorm wind and hail are typically higher than for tornadoes because they are more common. A 15% probability for a tornado means significantly above normal odds of a tornado nearby, which should be taken seriously, even though the number seems low. Note: The peak daily tornado probabilities in the most tornado prone portions of the country (Plains and Southeast) are slightly above 2%. Therefore, most days with any tornado probabilities are well above climatology.
Convective Outlook Issuance Times
Hover over a time to see it in your local timezone
Conditional Intensity
The SPC will represent these intensity forecasts as "Conditional Intensity Groups" (CIG) or more simply, "Intensity Levels". These three intensity distributions (CIG1, CIG2, and CIG3) will be utilized to communicate increasing intensity of significant severe hazards, should severe hazards occur. These new Conditional Intensity Groups will be visible on the SPC Severe Weather Outlook Day 1, 2, and 3 graphics and disseminated through the SPC Outlook PTS product, replacing the current operational 'SIGN' label.
Visual Representation of these Intensity Groups will be as follows:
Intensity Level 1 (CIG1)
Intensity Level 2 (CIG2)
Intensity Level 3 (CIG3)
Intensity Distribution by Conditional Intensity Group
Below are the reference intensity distributions forecasters are aiming for when each Conditional Intensity Group is introduced. Note: This is the target over a large number of events and is unlikely to verify for a single event due to the low sample size.
Tornado
Wind
Hail
A longer (40 minute) video with an in-depth explanation of these changes can be found here.
Probability to Category Conversion Tables
| Tornado | ||||
| 60 | 3 (ENH) | 5 (HIGH) | 5 (HIGH) | 5 (HIGH) |
|---|---|---|---|---|
| 45 | 3 (ENH) | 4 (MDT) | 5 (HIGH) | 5 (HIGH) |
| 30 | 3 (ENH) | 4 (MDT) | 5 (HIGH) | 5 (HIGH) |
| 15 | 3 (ENH) | 3 (ENH) | 4 (MDT) | 4 (MDT) |
| 10 | 2 (SLGT) | 3 (ENH) | 3 (ENH) | 3 (ENH) |
| 5 | 2 (SLGT) | 2 (SLGT) | 3 (ENH) | not used |
| 2 | 1 (MRGL) | 1 (MRGL) | 2 (SLGT) | not used |
| <CIG1 | CIG1 | CIG2 | CIG3 | |
| Wind | ||||
| 90 | 3 (ENH) | 4 (MDT) | 5 (HIGH) | 5 (HIGH) |
|---|---|---|---|---|
| 75 | 3 (ENH) | 4 (MDT) | 5 (HIGH) | 5 (HIGH) |
| 60 | 3 (ENH) | 4 (MDT) | 5 (HIGH) | 5 (HIGH) |
| 45 | 3 (ENH) | 3 (ENH) | 4 (MDT) | 5 (HIGH) |
| 30 | 2 (SLGT) | 3 (ENH) | 3 (ENH) | not used |
| 15 | 2 (SLGT) | 2 (SLGT) | 3 (ENH) | not used |
| 5 | 1 (MRGL) | 1 (MRGL) | 2 (SLGT) | not used |
| <CIG1 | CIG1 | CIG2 | CIG3 | |
| Hail | |||
| 60 | 3 (ENH) | 4 (MDT) | 4 (MDT) |
|---|---|---|---|
| 45 | 3 (ENH) | 3 (ENH) | 4 (MDT) |
| 30 | 2 (SLGT) | 3 (ENH) | 3 (ENH) |
| 15 | 2 (SLGT) | 2 (SLGT) | 3 (ENH) |
| 5 | 1 (MRGL) | 1 (MRGL) | 2 (SLGT) |
| <CIG1 | CIG1 | CIG2 | |
| Day 3 Total Severe | |||
| 60 | 3 (ENH) | 4 (MDT) | 4 (MDT) |
|---|---|---|---|
| 45 | 3 (ENH) | 3 (ENH) | 4 (MDT) |
| 30 | 2 (SLGT) | 3 (ENH) | 3 (ENH) |
| 15 | 2 (SLGT) | 2 (SLGT) | 3 (ENH) |
| 5 | 1 (MRGL) | 1 (MRGL) | 2 (SLGT) |
| <CIG1 | CIG1 | CIG2 | |
Text Narrative
The text narrative is written in scientific language and is intended for sophisticated users, though it begins with a summary for general understanding.
- Initial Summary: The text begins by listing severe thunderstorm risk areas by state and/or geographic region, followed by a succinct summary of the threat type(s) and timing, focused on the highest-risk areas.
- Synopsis: A synopsis section is usually included, giving a general overview of the weather pattern and emphasizing features that will influence the severe and general thunderstorm threats.
- Technical Discussion: The narrative technical discussion is usually separated by geographic areas. Within these individual areas, the text offers meteorological reasoning and justification for the type of coverage and intensity attendant to the severe weather threat.
Days 4–8 Severe Weather Outlook
This is a long-range forecast issued once a day by 400 am CST/CDT. It covers the period of 72 to 192 hours from 1200 UTC on the morning of product issuance.
Graphical Probabilistic Risk
This outlook consists of probabilistic forecasts depicting the severe weather threat with a separate graphic for each day (D4, D5, D6, D7, D8).
- Probabilistic Thresholds: Two thresholds of 15% and 30% can be forecast.
- Equivalency: Highlighted areas are equivalent to the 2-SLGT (Yellow) or 3-ENH (Orange) risks seen on the Day 1–3 outlooks.
- Headlines: On rare occasions, the outlook text will begin with a headline for the possibility of a severe weather outbreak.
No 15% Area Phrases
If no 15% areas are forecast, one of the following two phrases will be used:
- PREDICTABILITY TOO LOW: Used when severe storms may be possible, but the location or occurrence is in doubt due to large spread forecast scenarios.
- POTENTIAL TOO LOW: Used when 15% or greater severe probabilities appear highly unlikely on that day.
| Day | Period Covered |
|---|---|
| D4 | Day 4 |
| D5 | Day 5 |
| D6 | Day 6 |
| D7 | Day 7 |
| D8 | Day 8 |
| Note: Each day is a 12 UTC–12 UTC period. | |
Text Narrative
The text narrative is provided regardless of whether severe thunderstorm areas are included.
- Language: The outlook text is written in scientific language for sophisticated users.
- Technical Discussion: The technical discussion offers a general overview of the weather pattern influencing the severe thunderstorm threat during the entire five-day period, along with meteorological reasoning and justification.
- Headlines: On rare occasions, the text will begin with a headline for the possibility of a severe weather outbreak.
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National Weather Service National Centers for Environmental Prediction Storm Prediction Center 120 David L. Boren Blvd. Norman, OK 73072 U.S.A. spc.feedback@noaa.gov Page last modified: March 05 2026 01:03 UTC |
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