Area Forecast Discussion
Issued by NWS Atlanta, GA

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409 FXUS62 KFFC 170243 AFDFFC Area Forecast Discussion National Weather Service Peachtree City GA 1043 PM EDT Wed Aug 16 2017 .UPDATE... Convection ongoing across eastern sections of the forecast area so will need to hold onto isolated pops a little while longer. Otherwise...forecast in great shape and no changes planned. Deese && .PREV DISCUSSION... /issued 831 PM EDT Wed Aug 16 2017/ PREV DISCUSSION... /issued 320 PM EDT Wed Aug 16 2017/ SHORT TERM /Tonight through Thursday Night/... A warm, moist airmass remains across the forecast area. Convection has been slow to develop this afternoon and expect mainly scattered showers and isolated thunderstorms mainly this afternoon and early evening. Weak upper level ridging remains over the southeast through tomorrow before building west over the northern Gulf of Mexico. The flow aloft flattens some by tomorrow evening with a weak disturbance approaching north GA toward the end of the forecast period. A weak surface boundary will remain east of the area throughout the period as well. With upper level dynamics lacking, and only minimal instability expect diurnally driven convection today and tomorrow, with any development diminishing quickly with the loss of daytime heating. Guidance temperatures are in line, and continue to show overnight lows mainly in the 70s with afternoon highs tomorrow once again in the upper 80s to mid 90s. Heat indices tomorrow will once again be near 100. Atwell LONG TERM /Friday through Wednesday/... Made very few changes to the extended forecast grids with this cycle as medium-range models continue recent trends. Broad, weak mid/upper ridging breaks down over the weekend in response to the sharpening upper trough moving out of the northern/central plains into the Ohio Valley and Great Lakes before beginning to re-establish itself early next week. Please see the previous Long Term Forecast Discussion below. 20 Previous LONG TERM Forecast Discussion /Thursday Night through Tuesday/... A fairly progressive pattern, especially noted by the northern stream jet, will continue through the long term. Energy across the NW Canadian provinces will dig down into the upper mid-west and move eastward. While this energy does not sink too far south into our region, we will get some residual mid and upper level support, especially this weekend. Models are in disagreement with how much interaction we will see with these features, especially as it translates down to the surface. There are a couple key areas to look at. The first is the frontal passage progged to move through much of the area by early Saturday morning. The GFS is a bit more robust with this feature showing a lot more drying through the weekend across north GA; the front becoming stalled in central GA. The ECMWF shows a hint of the front moving through with some subtle drying Saturday into Sunday, but has this boundary becoming washed out/slipping north allowing moist/unstable airmass to surge a bit further northward as compared to the GFS by Sunday afternoon. Nevertheless, still feel better chances of convection will be across central GA, collocated with the boundary. All eyes are now on Monday, August 21st when the Eclipse is set to cross the SE during the afternoon hours. As the surface high moves off the mid-Atlantic, this will usher in moist southerly flow across the region. This is not good for those hoping for clear skies. Both models are still holding on to weak mid-level ridging, although impulses moving NE from a wave of low pressure across the GC region will aid in the formation of convection across the region. The GFS illustrating a bit more upper level support as opposed to the ECM. What does this mean in the end? Well, the pattern is not conducive for mostly clear skies. However, this is a typical summer time pattern across the region. So, viewing the Eclipse is still a potential, between all the building cumulonimbus and convection. One may just have to be at the right place at the right time. There is still a lot of uncertainty at this point. We will continue to update the forecast with new model guidance and hope the mid-level ridge strengthens with surface high pressure slowing its eastward progression. Temperatures will be at or above normal and will be largely dependent on overall cloud cover and convection. Temperatures fluctuations during the eclipse (Monday afternoon between 1pm and 3pm) may drop a few degrees, but is largely correlated with cloud cover and the path of totality. 26 AVIATION... 00Z UPDATE... SHRA/TSRA has been flirting with the TAF sites, especially ATL, PDK and MCN but thus far remained outside the 5 mile radii. Looks like VCSH will suffice for the remainder of the evening and a straight forward summertime forecast thereafter. Prob30 already in there for Thu and looks on target. //ATL CONFIDENCE...00Z UPDATE... High on all elements. Deese && .PRELIMINARY POINT TEMPS/POPS... Athens 74 92 74 92 / 20 30 20 40 Atlanta 75 91 75 91 / 20 30 20 40 Blairsville 69 86 69 86 / 20 40 20 40 Cartersville 74 91 74 89 / 20 30 20 40 Columbus 76 93 77 93 / 20 30 20 40 Gainesville 74 90 74 90 / 20 30 20 40 Macon 76 93 76 95 / 20 30 20 40 Rome 74 91 74 91 / 20 30 20 40 Peachtree City 74 91 74 91 / 20 30 20 40 Vidalia 77 94 77 94 / 20 30 20 50 && .FFC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...Deese LONG TERM....RW AVIATION...Deese is the U.S. government's official web portal to all federal, state and local government web resources and services.