Editing Storm Prediction Center (section)

===Categories===
[[File:June 27, 2020 SPC Day 1 Outlook.gif|thumb|left|An example of an Enhanced Risk day overlaid with the radar with Severe Thunderstorm Watches in effect.]]
A '''marginal risk''' day indicates storms of only limited organization, longevity, coverage and/or intensity, typically isolated severe or near-severe storms with limited wind damage, large hail and possibly a low tornado risk. Wind gusts of at least {{convert|60|mph|km/h}} and hailstones of around {{convert|1|in|cm}} in diameter are common storm threats within a marginal risk; depending on the sufficient wind shear, a tornado – usually of weak (EF0 to EF1) intensity and short duration – may be possible. This category replaced the "SEE TEXT" category on October&nbsp;22, 2014.<ref name="NewCategories"/>

A '''slight risk''' day typically will indicate that the threat exists for scattered severe weather, including scattered wind damage (produced by straight-line sustained winds and/or gusts of 60 to 70&nbsp;mph), scattered severe hail (varying in size from {{convert|0.25|in|cm}} to {{convert|1.75|in|cm}}) and/or isolated tornadoes (often of shorter duration and varying weak to moderate intensity, depending on the available wind shear and other sufficient atmospheric parameters). During the peak severe weather season, most days will have a slight risk somewhere in the United States. Isolated significant severe events are possible in some circumstances, but are generally not widespread.<ref name="convective outlooks"/>

An '''enhanced risk''' day indicates that there is a greater threat for severe weather than that which would be indicated by a slight risk, but conditions are not adequate for the development of widespread significant severe weather to necessitate a moderate category, with more numerous areas of wind damage (often with wind gusts of {{convert|70|mph|km/h}} to {{convert|80|mph|km/h}}), along with severe hail (occasionally over {{convert|2|in|cm}}) and several tornadoes (in some setups, isolated strong tornadoes are possible). Severe storms are expected to be more concentrated and of varying intensities. These days are quite frequent in the peak severe weather season and occur occasionally at other times of year. This risk category replaced the upper end of "slight" on October&nbsp;22, 2014, although a few situations that previously warranted a moderate risk were reclassified as enhanced (i.e. 45% wind or 15% tornado with no significant area).<ref name="NewCategories"/>

A '''moderate risk''' day indicates that more widespread and/or more dangerous severe weather is possible, with significant severe weather often more likely. Numerous tornadoes (some of which may be strong and potentially long-track), more widespread or severe wind damage (often with gusts over {{convert|80|mph|km/h}}) and/or very large/destructive hail (up to or exceeding {{convert|3|in|cm}} in diameter) could occur. Major events, such as large [[tornado outbreak]]s or widespread straight-line wind events, are sometimes also possible on moderate risk days, but with greater uncertainty. Moderate risk days are not terribly uncommon, and typically occur several times a month during the peak of the severe weather season, and occasionally at other times of the year. Slight and enhanced risk areas typically surround areas under a moderate risk, where the threat is lower.<ref name="convective outlooks"/>

A '''high risk''' day indicates a considerable likelihood of significant to extreme severe weather, generally a major tornado outbreak or (much less often) an extreme [[derecho]] event. On these days, the potential exists for extremely severe and life-threatening weather. This includes a large number of tornadoes - many of which will likely be strong to violent and on the ground for a half-hour or longer, or widespread and very destructive straight-line winds, likely in excess of {{convert|100|mph|km/h}}. Hail cannot verify or produce a high risk on its own, although such a day usually involves a threat for widespread very large and damaging hail as well. Many of the most prolific severe weather days were high risk days. Such days are rare; a high risk is typically issued (at the most) only a few times each year (see [[List of Storm Prediction Center high risk days]]). High risk areas are usually surrounded by a larger moderate risk area, where uncertainty is greater or the threat is somewhat lower.<ref name="convective outlooks"/>

The Storm Prediction Center began asking for public comment on proposed categorical additions to the Day 1-3 Convective Outlooks on April 21, 2014, for a two-month period.<ref>{{cite web|title=Experimental SPC Day 1, 2, 3 Convective Outlook Change Public Comment Page|url=http://www.spc.noaa.gov/exper/dy1-3example/|website=Storm Prediction Center|publisher=National Oceanic and Atmospheric Administration|access-date=April 21, 2014|archive-date=April 24, 2014|archive-url=https://web.archive.org/web/20140424123623/http://www.spc.noaa.gov/exper/dy1-3example/|url-status=live}}</ref> The Storm Prediction Center broadened this system beginning on October&nbsp;22, 2014 by adding two new risk categories to the three used originally. The new categories that were added are a "marginal risk" (replacing the "SEE TEXT" contours, see below) and an "enhanced risk". The latter is used to delineate areas where severe weather will occur that would fall under the previous probability criteria of an upper-end slight risk, but do not warrant the issuance of a moderate risk. In order from least to greatest threat, these categories are ranked as: marginal, slight, enhanced, moderate, and high.<ref>{{cite news|title=Forecasters Adding New Layers of Storm Outlooks|url=https://abcnews.go.com/m/story?id=21567394&sid=81|agency=[[Associated Press]]|website=[[ABC News (United States)|ABC News]]|publisher=[[The Walt Disney Company]]|date=January 17, 2014|archive-date=March 4, 2016|access-date=June 29, 2020|archive-url=https://web.archive.org/web/20160304194954/http://abcnews.go.com/m/story?id=21567394&sid=81|url-status=live}}</ref><ref>{{cite news|title=Forecasters adding layers of storm outlooks|url=http://www.arkansasonline.com/news/2014/jan/17/forecasters-adding-new-layers-storm-warnings/|agency=Associated Press|newspaper=[[Arkansas Democrat-Gazette]]|date=January 17, 2014}}</ref><ref>{{cite news|title=A better outlook: SPC revises its severe categories|url=http://www.wusa9.com/story/weather/2014/03/27/spc-severe-thunderstorms-tornadoes-hail/6974379/|website=[[WUSA (TV)|WUSA]]|publisher=[[Gannett Company]]|date=March 28, 2014|access-date=March 30, 2014|archive-date=April 26, 2014|archive-url=https://web.archive.org/web/20140426215509/http://www.wusa9.com/story/weather/2014/03/27/spc-severe-thunderstorms-tornadoes-hail/6974379/|url-status=dead}}</ref>
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