The National Weather Service issued a hazardous weather outlook for Cobb County and other parts of north and central Georgia for Tuesday, June 25.

The outlook includes the possibility of isolated to scattered thunderstorms, mostly affecting the south-central portion of the state.

A more widespread and longer-term forecast is for a very high heat index, ranging from the upper 90s to around 100 degrees.  This heat wave is expected to last through next Monday.

In this article, you will learn:

1. What is in today’s National Weather Service alert
2. What counties are included in the alert
3. What is meant by the terms “isolated” and “scattered”
4. What is the heat index
5. About the National Weather Service and what it does

What is in the statement?

The statement gives the following details:

This Hazardous Weather Outlook is for portions of North and

Central Georgia.

.DAY ONE…Today and Tonight…

Isolated thunderstorms will be possible over portions of south-

central Georgia this afternoon.

Very high heat index values in the upper 90s and near 100 are

expected this afternoon in central Georgia.

.DAYS TWO THROUGH SEVEN…Wednesday through Monday…

Scattered thunderstorms will be possible over much of the area

each day from Wednesday through next Monday. Storms that develop

will be capable of producing lightning, heavy rain, and gusty

winds.

Extreme heat will also be possible across much of the area through

next Monday, with heat index values around or above 100 each

afternoon.

What counties are affected?

The following counties are included in the hazardous weather outlook:

Baldwin, Banks, Barrow, Bartow, Bibb, Bleckley, Butts, Carroll, Catoosa, Chattahoochee, Chattooga, Cherokee, Clarke, Clayton, Cobb, Coweta, Crawford, Crisp, Dade, Dawson, DeKalb, Dodge, Dooly, Douglas, Emanuel, Fannin, Fayette, Floyd, Forsyth, Gilmer, Glascock, Gordon, Greene, Gwinnett, Hall, Hancock, Haralson, Harris, Heard, Henry, Houston, Jackson, Jasper, Jefferson, Johnson, Jones, Lamar, Laurens, Lumpkin, Macon, Madison, Marion, Meriwether, Monroe, Montgomery, Morgan, Murray, Muscogee, Newton, North Fulton, Oconee, Oglethorpe, Paulding, Peach, Pickens, Pike, Polk, Pulaski, Putnam, Rockdale, Schley, South Fulton, Spalding, Stewart, Sumter, Talbot, Taliaferro, Taylor, Telfair, Toombs, Towns, Treutlen, Troup, Twiggs, Union, Upson, Walker, Walton, Warren, Washington, Webster, Wheeler, White, Whitfield, Wilcox, Wilkes, Wilkinson

What is meant by “isolated” and “scattered”?

The NWS defines “isolated” as follows:

A National Weather Service convective precipitation descriptor for a 10 percent chance of measurable precipitation (0.01 inch). Isolated is used interchangeably with few.

“Scattered” has the following definition:

When used to describe precipitation (for example: “scattered showers”) – Area coverage of convective weather affecting 30 percent to 50 percent of a forecast zone (s).

Isolated thunderstorms and scattered thunderstorms are two terms used to describe different distributions of thunderstorm activity within a particular area. The main difference lies in the extent of coverage and how the thunderstorms are spatially distributed:

1. Isolated Thunderstorms:
   • Isolated thunderstorms are relatively rare occurrences that happen sporadically and are generally confined to a limited area.
   • These thunderstorms are often characterized by being few and far between, with significant gaps between individual storm cells.
   • Typically, isolated thunderstorms cover less than 20% of the forecast area.
   • Despite their isolated nature, these storms can still be intense and may produce heavy rain, lightning, gusty winds, and possibly hail.
2. Scattered Thunderstorms:
   • Scattered thunderstorms are more widespread than isolated thunderstorms and cover a larger portion of the forecast area.
   • In a scattered thunderstorm scenario, numerous individual thunderstorms develop, but they are not continuous or widespread enough to be classified as a “line” or “cluster” of storms.
   • Scattered thunderstorms generally cover between 30% to 50% of the forecast area.
   • Although scattered thunderstorms are more widespread, they still leave considerable gaps between storm cells, and not everyone within the forecast area will necessarily experience a thunderstorm.

In summary, isolated thunderstorms are fewer in number and more localized, covering a smaller area with significant gaps between storms, while scattered thunderstorms are more widespread, covering a larger area with numerous individual storms occurring somewhat randomly across the forecast area.

What is the heat index?

The NWS defines the heat index as follows on its website:

The heat index, also known as the apparent temperature, is what the temperature feels like to the human body when relative humidity is combined with the air temperature. This has important considerations for the human body’s comfort. When the body gets too hot, it begins to perspire or sweat to cool itself off.

Chart from NOAA showing relationship between relative humidity and temperature in heat index

About the National Weather Service

The National Weather Service (NWS) is a part of the National Oceanic and Atmospheric Administration (NOAA).

The NWS describes its role as follows:

“The National Weather Service (NWS) provides weather, water, and climate forecasts and warnings for the United States, its territories, adjacent waters and ocean areas, for the protection of life and property and the enhancement of the national economy. 

“These services include Forecasts and Observations, Warnings, Impact-based Decision Support Services, and Education in an effort to build a Weather-Ready Nation. The ultimate goal is to have a society that is prepared for and responds to weather, water and climate events.”

>>> Read all the Cobb County Courier climate and weather coverage by following this link.