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Good morning!

Hurricane Sally is making her way to the coast, but the winds this morning have dropped to 85 mph, so she has weakened overnight. But being the slow mover that she is (you know... "waitin' on a women" ūüôā¬†), she will dump a LOT of rain once she comes ashore.¬†

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Our focus now is on the potential for heavy rain across north Georgia. The axis of the heaviest rain has been slowly shifting south as the future track of Sally has done the same. The latest WPC forecast has shrunk the heaviest rain just a little bit from the previous run. 

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This is the full NWS Hydrologic forecast from this morning.

 

And this is the Weather Prediction Center's Excessive Rainfall discussion for Day 2 and Day 3.

 

The NWS Atlanta discussion.

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SHORT TERM /Today through Wednesday/...
Current satellite loop shows Hurricane Sally due south of Mobile Bay. The latest forecast shows it slowly moving northward making landfall near the MS/AL border around daybreak Wed morning. There is also a weak cold front oriented from NW to SE across north and portions of central GA this morning. This front is acting as a catalyst for some weak showers that have been fairly steady this morning. They appear to be growing so will continue with a chance of showers this morning. The front is expected to push a bit further south today before being pushed back northward Wed as Sally moves to the NE into the extended.

With Sally pushing onshore in the the next 24 hours moisture will steadily increase across north and central Georgia. Precipitable water values are currently in the 1.6 to 1.8 in range and will increase to 2" through Wed. As Sally near the state. a high pressure ridge nosing down the Eastern seaboard helps keep more stable conditions in place over the area. Looks like the heaviest precip from Sally will begin to push into western portions of the state Wed night and continue into the extended forecast periods.

With increasing precip chances temps today will get up into the upper 70's and lower 80's. Temps Wed will stay mainly in the 70's.

.LONG TERM /Wednesday Night through Monday/...
The main concern for the long term continues to be the effects of Sally on the forecast area. The Official forecast from the NHC takes Sally across roughly central GA Thursday night and Friday as a tropical depression.

Heavy rain potential starts to ramp up Wednesday night and will continue through Thursday for much of N and portions of central GA. Heavy rainfall potential could continue Thursday night into Friday for portions of north and east GA. Along with the heavy rain potential, you can't rule out the possibility for isolated tornadoes over the far SW CWA Wednesday Night from about CSG to MCN and south.

Once the remains of Sally passes the area later Friday, a cold front is expected to move south over the area Friday night and early Saturday.
This will diminish rain chances Friday night into Sunday
. The European and GFS are not in very good agreement here and that will just have to be adjusted with time.

.HYDROLOGY...
Potential rainfall from Sally could range 3 to 8 inches with locally higher amounts centered roughly along the I-85 and I-20 corridors, with slightly less amounts over the far NW counties and the counties S and E of MCN. This could lead to Flash flooding or river flooding for many areas and a flash flood watch will likely be issued later today. Please note that any shift of Sally's track will shift the axis of heavy rain as well.

 

I'll keep it short since I'm making updates in three places. ūüôā¬†I need to drink my coffee.¬†I will be updating all day as usual, so please check back often for the latest information.

Have a great Tuesday!

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NWS Atlanta

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Little changes to near term trends as forecast largely on track with wedge building in from the NE and continued stratus deck over much of the area (sans the far north). Axis of showers and associated pops should shift farther south this afternoon into primarily
central GA though isolated development could linger in parts of the north. Main focus still on the heavy rain and flooding threat
beginning late Wed with Sally tracking inland to our west. Will likely have a Flash Flood Watch issued with this main afternoon package.

 

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Whitfield-Murray-Fannin-Gilmer-Union-Towns-Gordon-Pickens-Dawson-
Lumpkin-White-Floyd-Bartow-Cherokee-Forsyth-Hall-Banks-Jackson-
Madison-Polk-Paulding-Cobb-North Fulton-Gwinnett-Barrow-Clarke-
Oconee-Oglethorpe-Wilkes-Haralson-Carroll-Douglas-South Fulton-
DeKalb-Rockdale-Walton-Newton-Morgan-Greene-Taliaferro-Heard-Coweta-
Fayette-Clayton-Spalding-Henry-Butts-Jasper-Putnam-Hancock-Warren-
Troup-Meriwether-Pike-Upson-Lamar-Monroe-Jones-Baldwin-Washington-
Glascock-Jefferson-Harris-Talbot-Taylor-Crawford-Bibb-Twiggs-
Wilkinson-Muscogee-Chattahoochee-Marion-Schley-Macon-Peach-Houston-
Stewart-Webster-Sumter-Dooly-
Including the cities of , Griffin, Lumpkin, Conyers, Cartersville,
Gainesville, Calhoun, Covington, Americus, Columbus, Newnan,
Marietta, Carrollton, Atlanta, Decatur, Peachtree City, Athens,
Rome, Macon, Warner Robins, Lawrenceville, Dahlonega, East Point,
Douglasville, Cleveland, and Milledgeville
324 PM EDT Tue Sep 15 2020

...FLASH FLOOD WATCH IN EFFECT FROM WEDNESDAY AFTERNOON THROUGH FRIDAY MORNING...

The National Weather Service in Peachtree City has issued a

  • * Flash Flood Watch for the majority of north and central Georgia,¬†except for far northwest Georgia and southeast central Georgia.
  • * From Wednesday afternoon through Friday morning
  • * Periods of heavy rainfall are expected across the area with the¬†outer rain bands of Hurricane Sally as it tracks inland west of¬†the area Wednesday and Thursday, then weakening as a tropical¬†depression by the time it tracks across the central portion of the¬†area into early Friday. Associated rainfall totals in excess of 3¬†to 4 inches and areas of 5 to 6 inches are expected with even¬†locally higher amounts possible. The highest amounts look to be in¬†a swath centered along the I-85 corridor, though this could shift¬†with future forecast updates.
  • * Soils are expected to become quickly saturated and runoff from¬†heavy rain will lead to a threat of flash flooding. Some of the¬†rivers, small creeks, and streams could also respond with flooding¬†that may linger beyond the watch period.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flash Flood Watch means that conditions may develop that lead to Flash Flooding. Flash Flooding is a very dangerous situation. You should monitor later forecasts and be prepared to take action should Flash Flood Warnings be issued.

 

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