A Flood Watch has been issued for much of North/Northwest Georgia. The Watch is in effect for Bartow, Catoosa, Chattooga, Cherokee, Cobb, Dade, Dawson, Fannin, Floyd, Gilmer, Gordon, Haralson, Lumpkin, Murray, Paulding, Pickens, Polk, Towns, Union, Walker, White, and Whitfield Counties. Total rainfall amounts of 2-4″ are expected in the watch area, and isolated amounts of up to 6″ possible. Both flooding and flash flooding are possible, especially overnight when the longest duration, heaviest rainfall is expected.
The Weather Prediction Center has continued to show much of North Georgia under a slight (level 2/4) risk for flash flooding. The rest of the region lies in a marginal (level 1/4) risk.
The reason for this risk is a “firehose” of moisture expected to move slowly east ahead of the front. The animation below shows this very well starting tat 8 a.m. Friday lasting through 7 p.m. Saturday. Multiple rounds of heavy rain are expected to hit the same areas over and over as the front slowly marches east. The simulated radar below shows this well from late Friday through 11 p.m. on Saturday.
The heaviest rainfall totals are expected to fall roughly along and north of the I-20 to I-85 corridor in North Georgia. Total rainfall amounts of 2-4″ appear likely over the entire area. With current 30-day rainfall deficits between 3-6″ for the northern half of the state, this could effectively wipe out the current short term drought in one go. The latest short-range models show 1-3″ of additional rain through noon Saturday on top of the 1/2-1″ that have already fallen. More would be coming during the afternoon.
While it has been very dry across the region lately, this can counterintuitively raise the flash flooding risk. Dry ground doesn’t do nearly as good a job at soaking up water due to compaction. This means heavy rains can quickly run-off enough to cause problems. Couple that with this being the dead of winter and trees not soaking in as much either, and flash flooding will certainly be possible.
Current analysis shows most of the region would need 3-4″ of rain in 6 hours to have many flash flooding issues, but that number could drop as the heavy bands move through on Friday night…