A widespread damaging wind event, known as a Derecho, with isolated embedded tornadoes occurred in southern Illinois and parts of southeast Missouri. Peak wind gusts were measured over 80 mph at Marion and Carbondale, IL. The peak gust recorded by the automated system at the Carbondale airport was 81 mph before the system failed. An observer at the airport visually observed a separate anemometer located on the rooftop reach 106 mph. The automated system measured a sustained wind of 68 mph before failing. Extensive tree and power line damage occurred in the Murphysboro, Carbondale, and Marion areas of southern Illinois and Perry and Bollinger Counties of southeast Missouri. Numerous structures were damaged in the Marion, Carbondale, and Murphysboro areas. While injuries were reported, an approximate count was not available. One fatality occurred in Jackson County when a tree fell on a home, causing an elderly man to fall to his death. State disaster declarations were granted for Jackson, Williamson, and Franklin Counties in Illinois. Curfews and states of emergency were declared locally. The Williamson County airport near Marion reported a peak gust of 86 mph. There was extensive damage at the airport, including hangar buildings. Hail was around 2 inches in diameter in some areas. There was a report of windows broken out of vehicles on the east side of Carbondale. The storm continued into western Kentucky producing golf ball size hail in Marion Kentucky. Several communities in southeast Missouri had received strong winds and microbursts, with winds up to 90 MPH occurring in Ripley County. ...
North American summers are hot; most summers see heat waves in one or more parts of the United States. Heat is one of the leading weather-related killers in the United States, resulting in hundreds of fatalities each year and even more heat-related illnesses.
A little explainer video on shelf clouds. We're always thrilled to have your reports coming in, however, it's important that those reports are accurate. Many viewers sending photos of what they called wall clouds, but were actually shelf clouds. Wall clouds can create tornadoes, shelf clouds do not.
SPC issues Day 1, Day 2, and Day 3 Convective Outlooks that depict non-severe thunderstorm areas and severe thunderstorm threats across the contiguous United States, along with a text narrative. The categorical forecast specifies the level of the overall severe weather threat via numbers (e.g., 5), descriptive labeling (e.g., HIGH), and colors (e.g., magenta). The probabilistic forecast directly expresses the best estimate of a severe weather event occurring within 25 miles of a point. The text narrative begins with a listing of severe thunderstorm risk areas by state and/or geographic region. This is followed by a concise, plain-language summary of the type(s) of threat along with timing that is focused on the highest-risk areas. The rest of the outlook text is written in scientific language for sophisticated users. This technical discussion usually includes a synopsis section to provide a general overview of the weather pattern, emphasizing features that will influence the severe and general thunderstorm threats. Additional sections of the discussion are usually separated by geographic areas. Within these individual geographic areas, the text offers meteorological reasoning and justification for the type of coverage and intensity attendant to the severe weather threat.
SPC also issues a Day 4-8 Severe Weather Outlook that similarly depicts severe thunderstorm threats across the contiguous United States and contains a technical discussion.
Severe Weather Risks 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.
TSTM (light green) - General or non-severe thunderstorms - Delineates, to the right of a line, where a 10% or greater probability of thunderstorms is forecast during the valid period.
1-MRGL (dark green) - Marginal risk - An area of severe storms of either limited organization and longevity, or very low coverage and marginal intensity.
2-SLGT (yellow) - Slight risk - An area of organized severe storms, which is not widespread in coverage with varying levels of intensity.
3-ENH (orange) - Enhanced risk - An area of greater (relative to Slight risk) severe storm coverage with varying levels of intensity.
4-MDT (red) - Moderate risk - An area where widespread severe weather with several tornadoes and/or numerous severe thunderstorms is likely, some of which should be intense. This risk is usually reserved for days with several supercells producing intense tornadoes and/or very large hail, or an intense squall line with widespread damaging winds.
5-HIGH (magenta) - High risk - An area where a severe weather outbreak is expected from either numerous intense and long-tracked tornadoes or a long-lived derecho-producing thunderstorm complex that produces hurricane-force wind gusts and widespread damage. This risk is reserved for when high confidence exists in widespread coverage of severe weather with embedded instances of extreme severe (i.e., violent tornadoes or very damaging convective wind events). ...