Area Forecast Discussion
Issued by NWS Atlanta, GA

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569 FXUS62 KFFC 211900 AFDFFC Area Forecast Discussion National Weather Service Peachtree City GA 300 PM EDT Fri Jun 21 2024 ...Afternoon Area Forecast Discussion... .SHORT TERM...
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(This afternoon through Saturday) Issued at 254 PM EDT Fri Jun 21 2024 500 mb analysis shows a stout upper-level ridge positioned over the eastern CONUS while high pressure prevails at the surface. A relatively disorganized area of showers and thunderstorms currently offshore about 80 miles ESE of Brunswick, Georgia will continue its WNW track toward the Georgia and northeastern Florida coasts today. Per the NHC, there is a 60% chance that this system could briefly become a tropical depression before it reaches the coast. Currently, a Cu field has developed across much of the area with enough insolation to drive temperatures into the lower 90s to mid- 90s outside of the mountains. Isolated showers (and possibly a thunderstorm) associated with the aforementioned system could clip the far southeastern portion of the forecast area. While marginal instability is progged across said area, would not be surprised if no thunderstorms occur as little to no lightning is depicted via GLM (Geostationary Lightning Mapper) with the system right now. A slight chance (up to around 20% PoPs) for showers is expected overnight across said area. Overnight lows will range from the upper 60s to mid-70s (with slightly cooler conditions in the mountains). As the tropical moisture associated with the system pushes farther into central Georgia amid the prevailing easterly synoptic flow, PWAT will climb to 1.5" to 2.0". As a result, expecting much of east- central Georgia to have at least a slight chance (~20%) to a chance (up to ~50%) for showers and thunderstorms tomorrow afternoon. The HREF is progging 1000-1500 J/kg of MUCAPE, but the hi-res guidance reveals abysmal lapse rates, so the potential for strong/severe storms is low. The increasing moisture will contribute to increasing heat index values (nearing 100 degrees across much of the area). Highs will be in the mid-90s outside of the mountains. Martin
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&& .LONG TERM...
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(Sunday morning through next Thursday) Issued at 254 PM EDT Fri Jun 21 2024 On Sunday, subtropical high begins to shift west as trough begins to form and dig into the NE going into Monday. Shortwave within the upper level flow will amplify this trough on Monday and help push a front towards the area. Front can be noted on the 925 mb surface, as the surface reflection is heavily modified by the afternoon sun. This front will likely stall and not do much other than push some lower humidities at the surface into the area Monday evening into overnight, before a surface high builds in and moisture returns by Tuesday. Diurnally driven convection looks to be possible for most days given moisture and strong daytime heating that will allow us to hit convective temperatures. Heat will be the primary weather story in the long term. NBM is showing temperatures in the mid to upper 90s, including even a few triple digits, Sunday through Wednesday. Overnight lows also would not provide for much relief falling into the low to mid 70s. Unlike our previous spell of heat, moisture looks to be a bit more present, so heat indices creep up into the triple digits again and heat products may be warranted. However. There is some uncertainty around afternoon temperatures, especially given the chances for diurnal convection. One bias we have noted in the longer term guidance during our diurnal convection season is for the blend to give an actual high that is a bit too high, as we reach convective temperature and produce rain and cloud cover across much of the area well before those highs can be realized. You can see a reflection of this within the NBM percentiles, where the NBM 90th and 10th percentile spread is 10 degrees or more at many point locations, representative of models which are convecting and cooling. The forecast will continue to reflect the higher end heat chances, and once we have a better handle on what type of coverage we may have on afternoon convection via short term guidance, more concrete decisions can be made around heat related products. At the tail end of the long term, uncertainty is a bit higher. Model ensembles show a system approaching the eastern CONUS, but their is decent amount of uncertainty around timing and strength. Should a front move through, PoPs will certainly increase, but current PoPs reflect better the uncertainty around the situation. Lusk
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&& .AVIATION...
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(12Z TAFS) Issued at 646 AM EDT Fri Jun 21 2024 VFR conditions are expected to persist through the TAF period, with a FEW-SCT cu field around 050-060 developing during the afternoon hours. Chances for SHRA/TSRA are forecast to remain south and east of all TAF sites today. Winds will be primarily E through the period, at 5 kts or less during the morning hours and increasing to 6-10 kts after 17Z, then diminishing to 5 kts or less once again after sunset and overnight. IFR level clouds will be possible in the morning hours on Saturday, between 10-14Z, in east Georgia. These scattered IFR clouds could spread as far east as MCN/AHN towards the end of the TAF period. //ATL Confidence...12Z Update... Medium confidence on IFR clouds on Saturday morning. High confidence on all other elements. King
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&& .PRELIMINARY POINT TEMPS/POPS...
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Athens 69 93 72 96 / 0 10 10 20 Atlanta 72 95 75 96 / 0 0 10 10 Blairsville 64 88 67 89 / 10 10 10 20 Cartersville 69 95 72 96 / 0 0 0 10 Columbus 72 97 75 99 / 0 10 10 10 Gainesville 69 92 73 94 / 0 10 10 20 Macon 72 95 73 99 / 0 20 10 20 Rome 71 96 72 97 / 0 0 0 10 Peachtree City 69 96 72 98 / 0 0 0 10 Vidalia 74 92 73 96 / 20 60 20 50
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&& .FFC WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Martin LONG TERM....Lusk AVIATION...Martin