Conditional Intensity is information the Storm Prediction Center (SPC) adds to its Day 1, Day 2, and Day 3 Convective Outlooks to show how intense tornadoes, damaging winds, or hail could be if they occur. It is expressed in three Conditional Intensity Groups, labeled CIG1, CIG2, and CIG3, which communicate increasing intensity of significant severe hazards.
Coverage versus intensity
The regular outlook probabilities describe how likely a severe hazard is near a point. Conditional Intensity answers a different question, which SPC frames for tornadoes as: if a tornado occurs, how likely is it to be EF2, EF3, or EF4?
The two can point in different directions. SPC gives the example of a wind event with many reports but few significant ones, which could have high coverage probabilities and lower intensity, and the reverse, a day with one or two high-end storms, low coverage, and higher intensity.
What the groups mean
For tornadoes, SPC pairs CIG1, CIG2, and CIG3 with a reasonable maximum of EF2, EF3, and EF4. NWS Little Rock describes CIG3 as implying the potential for a historic outbreak.
For hail, CIG1 points to greater potential for stones 2 inches or larger and CIG2 to stones 3.5 inches or larger. There is no CIG3 for hail.
For wind, CIG1 points to peak gusts of 65 knots (75 mph) or more, CIG2 to setups where a bow echo or derecho is possible, and CIG3 to a high-end derecho that is usually already under way.
What it replaced
Before this change, a hatched area marked at least a 10 percent chance of significant severe weather: EF2 or stronger tornadoes, hail 2 inches or larger, or winds of 65 knots or more. The groups replaced that hatching and are no longer tied to the 10 percent floor.
Conditional Intensity began with the 1630 UTC Day 1 outlook on 03/03/26, after SPC forecasters had produced the forecasts experimentally since late 2021. SPC said the outlook categories, Marginal through High, would stay the same.
What it does not tell you
A CIG is conditional. It describes how strong a hazard could get if storms produce it, not whether storms will form or reach a given place, so most places inside a CIG3 tornado area with a low tornado probability are still unlikely to see a tornado.
The groups are a forecast of reasonable maximum intensity based on the environment and expected storm mode. Read them together with the probabilities and categories, not in place of them.