923 FXUS62 KFFC 191545 AFDFFC Area Forecast Discussion National Weather Service Peachtree City GA 1145 AM EDT Sun Sep 19 2021 .UPDATE... Scattered to numerous showers have been ongoing across mainly portions of the Atlanta metro into northwest Georgia through the morning. Heading into the afternoon, additional development is expected. Locally heavy rainfall remains a threat given the rich tropical moisture in place. The most favored area for localized flooding concerns remains across northwest Georgia extending southward into west central Georgia through the remainder of today into tonight. Any additional heavy rainfall totals in this region would fall on areas that have seen more substantial amounts thus far. RW && .PREV DISCUSSION... /Issued 736 AM EDT Sun Sep 19 2021/ ..Updated for 12z Aviation Discussion... PREV DISCUSSION... /Issued 335 AM EDT Sun Sep 19 2021/ SHORT TERM /Today through Monday/... Challenging forecast for today and Monday. The main concern will revolve around the potential for heavy rainfall. 500mb analysis shows the remnant low from Nicholas across SW LA/far SE TX. Further east across the CWA, a skinny ridge extends northward from Florida. The ridge across the CWA is expected to break down a bit as the remnant low ejects north and east into the Mid Mississippi River Valley. The associated longwave trough will slowly push east through Monday. At the surface, weak high pressure will continue across the CWA. The high will exert the most influence across the east central portion of the CWA. On the periphery of this surface ridge and westward, will be the greatest potential for precipitation for today and tomorrow. PWATs remain higher than normal for this time of year. Have noticed that for the far NE portion of the forecast area, values are lower than what the models were progging yesterday, closer to 1.5". Outside of the NE forecast area, PWATs today will average around 2". Even higher values are forecast to advect northward overnight and into Monday. Areas along the GA/AL border received the highest amount of rainfall on Saturday. This area should once again have the highest potential for locally heavy rainfall today, especially the far NW corner of the CWA and near the Columbus area. Soils are not totally saturated, but steady on/off rainfall today should prime the area and have issued a Flash Flood Watch. Do think this watch may have to be extended in area and time for Monday as the really deep tropical moisture overspreads the CWA. Also, expecting quick rises on creeks/rivers under the watch area. With all of the cloud cover and steady precip around, MaxT values will be slightly lower and normal. However, warm overnight temps are likely. NListemaa LONG TERM /Monday Night through Saturday/... No major changes to the long term forecast with bouts of heavy possible rainfall through the first half of the week from saturated airmass via remnants of Nicholas situated over the SE. Still anticipating widespread showers from Monday into Wednesday as minor perturbations work its way through the SWly flow. Model guidance remains steady with saturated dewpoints in the low 70s across the area during the early parts of the week in tandem with precipitable water values ranging from 1.75 to 2.25 inches. QPF during this time is currently anticipated to be the highest across north GA, particularly across the N GA mountains, where orographic lift could lead to locally higher amounts. With that, nudged storm total rainfall forecast slightly from Monday through Wednesday to range from 0.75-1.5" across far north Georgia and 0.25-0.5" in central Georgia area. With saturated column and PWATS near double the moving avg for this time of year, expecting locally higher amounts across the area and would not be surprised if QPF totals were to fluctuate over next few forecast packages. Approaching the midweek, model guidance remains in good agreement that the shortwave trough will deamplify and shift NE as another, deeper digging trough and associated surface cold front move through the CWA on Wednesday night/Thursday morning, shunting out the remaining precip and saturated air mass by Thursday afternoon. After the cold front passage, the rest of the extended looks to remain dry as surface high sinks down over the Ohio River Valley. Increased cloud coverage and rain chances will limit diurnal temps on Monday and Tuesday, with highs mainly in the upper 70s to low 80s and overnight lows only dropping into the low 70s. Good news is that by Friday morning, low temperatures are expected to drop into the 50s across the area, with even some upper 40s possible in the higher elevations of the N GA mountains. Morgan AVIATION... 12Z Update... A period of LIFR is possible at ATL towards 12Z. A lull in the precip may occur during the mid morning, but do expect precip to become more widespread by the late afternoon/evening. On/off rain should continue for most of the overnight hours. Thunder chances remain too small to mention at this time. Winds will remain on the east side. //ATL Confidence...12Z Update... Med confidence all elements. NListemaa && .PRELIMINARY POINT TEMPS/POPS... Athens 81 69 77 69 / 40 60 60 60 Atlanta 79 70 77 69 / 100 60 60 60 Blairsville 76 65 72 64 / 60 60 60 60 Cartersville 78 69 77 69 / 70 60 60 60 Columbus 79 71 82 71 / 80 60 60 40 Gainesville 78 68 74 68 / 50 60 60 60 Macon 83 71 81 70 / 50 60 60 50 Rome 78 70 78 70 / 80 70 70 60 Peachtree City 79 70 78 69 / 60 60 60 60 Vidalia 84 72 80 72 / 60 40 60 50 && .FFC WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch through Monday morning for the following zones: Bartow...Carroll...Catoosa...Chattahoochee...Chattooga... Cherokee...Cobb...Coweta...Dade...Douglas...Fayette...Floyd... Gilmer...Gordon...Haralson...Harris...Heard...Marion... Meriwether...Murray...Muscogee...North Fulton...Paulding... Pickens...Polk...South Fulton...Stewart...Talbot...Troup... Walker...Webster...Whitfield. && $$ SHORT TERM...RW LONG TERM....Morgan AVIATION...RW