Shows and thunderstorms are forecast throughout the day, but the strongest chance of heavy rain won't start until this evening when enough precipitation is forecast to possibly cause flooding on Big Creek in North Fulton.
The same warm and moist Gulf air that is allowing dense fog this morning will create conditions favorable for strong to severe thunderstorms this afternoon and evening, according to the National Weather Service. Some showers and thunderstorms could produce locally heavy rains over portions of north Georgia that are already saturated leading to flash flooding of small creeks, streams and low-lying flood-prone areas.
Storm total rainfall amounts of 1 to 3 inches are possible for north Georgia Thursday afternoon through early Friday, though for Alpharetta a half inch to three-quarters of an inch of rain is forecast. The area of concern would be mainly north of a line from Franklin through Mcdonough and Monroe to Homer. This would include the Atlanta metro area.
Weatherbug.com forecasts a 99 percent chance of rain from 8 p.m. Thursday to 7 a.m. Friday.
Isolated flash flooding will be possible if the heavy rain repeatedly moves over the same area. Also, storm drains and ditches in urban areas may become quickly clogged with debris and cause extensive street flooding and road ponding.
Minor flooding of some of the larger creeks or rivers is more likely with the expected storm total rainfall amounts. These would include Big Creek in Forsyth and North Fulton counties.
But the primary hazard could be the areas of dense fog that will make travel hazardous due to rapid drops in visibility. Strong to severe thunderstorms will bring possible isolated tornadoes, damaging wind, locally heavy rain and dangerous cloud-to-ground lightning this afternoon and tonight.
Highs today will be in the upper 60s, with South winds 10 to 15 mph. The low will be 51.