Understanding Severe Thunderstorm Risk Categories

In preparation for an increase in severe weather this month, we feel it’s important to provide a description of Severe Thunderstorm Risk Categories.

The Storm Prediction Center (SPC) is part of the National Weather Service (NWS).
The SPC is responsible for issuing watches for severe thunderstorms and tornadoes over the contiguous United States.

SPC issues Day 1, Day 2, and Day 3 Convective Outlooks that depict non-severe thunderstorm areas and severe thunderstorm threats across the U.S.

The level of categorical risk in the Day 1-3 Convective Outlooks is derived from probability forecasts of tornadoes, damaging winds, and large hail on Day 1, and a combined severe weather risk on Days 2 and 3.

SPC severe weather outlooks forecast events from organized convection such as supercells and squall lines…most capable of damage and injury from tornadoes, damaging winds, or large hail.

These outlooks are used as a forecast guide for local forecasters and provided to the general public.

Below…We have provided an detailed color chart that describes more in detail about the forecast threat of local severe weather events.

We have a Severe Weather Data page that list all these outlook forecasts, along with warnings and additional severe weather resources.

Click on the image to enlarge the chart.


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