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The sky was blue over Atlanta on Thursday morning, but the ground made a squishing sound if you walked across it, soaked from heavy rains the day before that left streets muddy with red Georgia clay.
And before the city has a chance to dry out from Wednesday’s storm, another storm threatens the Eastern United States with excessive rain that is “particularly concerning” to forecasters for cities like Atlanta, where another two to five inches may fall Friday into Saturday.
A similar amount of rain soaked Atlanta on Wednesday, filling some creeks to flood stage. A NASA computer model showed that topsoil saturation was over 65 percent, and in some cases even higher. The soppy ground will keep any new rainfall from soaking in, increasing the risk of flash flooding with any new rain this weekend.
If the region were to receive the higher end of the forecast rainfall, it could lead to substantial flash flooding and rapid rises in already elevated waterways, the National Weather Service office in Atlanta warned.
A wet couple of months have also left the ground at capacity elsewhere in the East, especially in the Northeast, where more rain will fall over the weekend. Over an inch of rain fell in Central Park in New York on Wednesday. And while the next round of rain there isn’t expected to be as significant as what is expected across the South, the rain forecast for Saturday into Sunday in the city could lead to minor urban, nuisance-type flooding.
Severe storms could produce tornadoes.
Severe storms with damaging wind gusts could produce tornadoes in Atlanta early Sunday morning. While that is not the main concern with this storm system, it is possible.
Tornadoes are more likely to form west and south of the city on Friday.
Storms that are ongoing Friday morning in Texas will move east during the day, creating the risk for tornadoes along the Gulf Coast states of Louisiana, Mississippi, Alabama and Florida.
There is still some hesitancy from forecasters on how bad the tornado threat may become. If the ingredients needed to form tornadoes — rising moist warm air and changing wind speeds with height — become more evident, forecasters are likely to increase the anticipated tornado risk in the coming days.
How the forecast could change.
A warm conveyor belt of moisture, similar to the atmospheric rivers that frequently affect the West Coast, will draw moisture across the South and into the Northeast.
The rain in the Northeast is expected to be less severe than in the South because the southern end of the storm will use most of the available moisture. The storm system is also expected to move quickly through the Northeast, limiting the amount of moisture that may fall. If the storm slows down or more moisture flows, the chances could increase, especially in New England, where the soil is soaked to similar or higher levels than in the Southeast — but that is not the likely scenario.
The moisture available in the South and the expected impact of higher-altitude winds will allow storms to train across the region. Training occurs when one storm forms over an area and, as it dumps a heavy amount of rain, creates the environment for another storm to form behind it, and so on. The longer the train, the more rain will fall over an isolated region, which is why one inch of rain could fall in one location, and a spot a few miles down the road might receive five times that.
The location of the heaviest rain will depend on where these thunderstorms line up.
The flood risk in the South is not likely to end soon. Toward the end of next week, more rain, on top of what may fall this weekend, is likely.
That means that for a while, walking across the grass will continue to feel more like treading on gelatin than solid ground.
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