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FXUS62 KFFC 181847 AFDFFC

Area Forecast Discussion National Weather Service Peachtree City GA 247 PM EDT Sat May 18 2024

Afternoon Area Forecast Discussion

SHORT TERM
(This afternoon through Sunday)
Issued at 210 PM EDT Sat May 18 2024

Water vapor satellite imagery and radar imagery depict the fetch of moisture and embedded convection that brought moderate to heavy rainfall across portions of central GA shifting south and east.
Isolated to scattered showers have begun to develop north of this area that was worked over by earlier rainfall, as cloud cover has begun to scatter out. SBCAPE has climbed to 1500-2000 J/kg across much of the CWA, so expect to see increasing coverage of showers as the afternoon continues. A shortwave/concentrated area of vorticity currently over TN/AL is tracking eastward, so also expect to see scattered to widespread thunderstorms develop across north GA over the next several hours. Some storms over N AL associated with this feature have been strong to severe, so expect that some storms across north GA will have similar intensity. The primary threats will be damaging wind gusts and hail up to 1" in diameter, with cloud-to-ground lightning and heavy rainfall also concerns. As this feature aloft draws closer and insolation increases across the rest of the CWA (at least where cloud cover clears out enough), the potential for isolated strong to severe storms farther south will increase. SPC has the entire CWA in a Marginal Risk, which makes sense given the ample bulk shear from a belt of strong winds aloft plus the shortwave, as well as increasing diurnally-driven instability.

Some of the CAMs suggest that convection could organize into lines/clusters late this afternoon into the evening due to the forcing aloft and convergence of outflow boundaries. As a result, some showers and storms could persist well after sunset, but in general, expect to see an overall decrease in coverage of convection as daytime heating ceases. The aforementioned shortwave axis will shift east of the CWA tomorrow (Sunday), but progged SBCAPE/MUCAPE of 500-1500 J/kg area-wide will support isolated to scattered showers and thunderstorms in the afternoon and early evening. A strong storm or two with gusty winds will be possible, but with little to no bulk shear and poor mid-level lapse rates expected, severe storms look to be unlikely. SPC has the entire CWA in General Thunder tomorrow.

Martin



LONG TERM
(Monday morning through next Friday)
Issued at 210 PM EDT Sat May 18 2024

No major weather impacts or forecast concerns expected in the long term period.

Positively tilted upper trough will continue slide east away from the east coast and southeast states Monday with dry NW flow over most of the area except for far NE portions of the state where rare upslope and isolated convection on the back side of a weak upper low is expected in the afternoon. Tuesday should be dry as upper ridging from the SW builds and a weak wave passes well to our north.

By Wednesday, large upper low centered over the northern Plains will be pushing east into the Great Lakes with a wide swath of Westerlies around it. The fringe of the Westerlies will move into north GA with increasing moisture and some life, could see isolated convection along and ahead of front in TN push south.
Front and SWly flow aloft pushes deeper into the state Thursday at which point spread in model guidance increases significantly with one or two clusters indicating a weak wave in the westerlies over the lower MS valley states early Friday morning which is a very favorable pattern for widespread showers and storms. Too soon to tell if conditions would be favorable for severe storms or very heavy rain, but with what we see now, does not appear to be too significant. This is supported by Day 7 and 8 SPC, WPC and CSU ML severe weather and heavy rainfall guidance.

Atlantic basin still indicates no tropical activity expected the next 7 days.

SNELSON



AVIATION
(18Z TAFS)
Issued at 122 PM EDT Sat May 18 2024

Expect CIGs to generally improve to low-VFR over the next couple hours. The main forecast challenge for the afternoon/evening is timing out convection and thus TEMPOs. Have opted to not do TEMPOs for MCN and CSG as the atmosphere is quite worked over from SHRA this morning. For the remaining sites (including ATL), have gone with TEMPOs for TSRA for either 20z-00z or 21z-01z. Expect conditions to deteriorate again overnight with widespread IFR and patchy LIFR expected, as well as fairly widespread MVFR VIS.
Current SW winds will go LGT to calm overnight, then pivot to NE tomorrow (Sunday) morning.

//ATL Confidence
18Z Update
Medium confidence on convection timing.
High confidence on all other elements.

Martin



PRELIMINARY POINT TEMPS/POPS
Athens 63 79 60 83 / 60 40 10 0 Atlanta 65 80 63 83 / 50 30 10 0 Blairsville 58 75 58 78 / 60 50 10 20 Cartersville 62 81 61 84 / 60 30 0 0 Columbus 66 84 66 85 / 50 20 10 0 Gainesville 63 78 61 82 / 60 50 10 10 Macon 65 81 63 83 / 50 40 10 0 Rome 63 83 62 85 / 60 20 0 0 Peachtree City 64 81 62 83 / 50 30 10 0 Vidalia 68 80 65 83 / 50 60 20 10

FFC WATCHES/WARNINGS/ADVISORIES
None.

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