396 FXUS62 KFFC 041547 AFDFFC Area Forecast Discussion National Weather Service Peachtree City GA 1147 AM EDT Sat Sep 4 2021 .UPDATE... No changes to the forecast this morning. Subsidence under both the surface ridge overhead and the upper level ridge to our west will aid in keeping the area dry. PoPs will remain out of the area throughout the day and night with light winds and high temperatures reaching the upper 80s. && .PREV DISCUSSION... /Issued 457 AM EDT Sat Sep 4 2021/ SHORT TERM /Today through Sunday/... As the morning begins, an upper level ridge remains centered over the lower Mississippi Valley and extending northward into the Great Lakes region. At the surface, high pressure is currently centered over the central Appalachians, which is promoting a dry easterly flow over much of north and central Georgia. As a combination of these factors, dry conditions will persist across north and central Georgia throughout the day today. Subsidence underneath the ridge will inhibit convective development today and precipitation is not expected across the area. Dewpoints will be in the 50s across the majority of north and central Georgia today, with the lowest values forecast in east-central Georgia where the greatest mixing is expected. Precipitable water values are furthermore expected to range from 0.50 to 0.75 inches throughout the short term period, which is well below the 10th percentile for PWATs in early September per sounding climatology. After a relatively cool start to the morning, with low temperatures in the 60s, increasing 1000-500 mb thickness values underneath the ridge will allow for gradually climbing daytime temperatures, with afternoon highs running near average today, in the mid to upper 80s, then 2-5 degrees above average on Sunday, in the upper 80s to low 90s. Taking these warm and dry conditions into account, relative humidity values are forecast to drop to a minimum of 30-40 percent across the majority of the forecast area this afternoon, but values will be well outside of fire danger thresholds. On Sunday, the upper level flow will decouple, with the southern portion of the ridge beginning to flatten out and the northern portion of the ridge quickly moving away to the east as an upper level trough drops southeastward towards the Great Lakes region. At the surface, the high pressure center will move offshore of the mid- Atlantic coast and the low-level flow will regain a more southerly component. This southerly flow will bring more Gulf moisture into the southeastern CONUS, allowing for dewpoints to start steadily climbing back into the 60s. A surface cyclone associated with the aforementioned shortwave will push a cold front southeastward towards north Georgia during the later part of the period. With increasing atmospheric moisture and broad forcing ahead of the approaching front, isolated showers and thunderstorm chances will begin to increase across far north Georgia during the afternoon hours on Sunday. King LONG TERM /Sunday Night through Friday/... As we move into the extended periods, expecting a few frontal boundaries and a few waves to push across the area. The upper level ridge in the short term will still be in place at the beginning of the extended periods but it will be weakening fast. The main upper level trough begins developing over the Great Lakes States Sunday and digs into the Southeastern U.S Monday into Tuesday. The associated surface cold front pushes into N GA Sunday night/Monday morning and weakens through Monday afternoon. It also appears to stall somewhere between ATL and MCN Monday night/Tuesday. This will bring increased moisture back in across the CWA and the boundary will act as a catalyst for diurnally driven convection through Wed/Thu. With the frontal boundary stalled over the state A developing tropical short wave over the central gulf pushes onshore near the AL/FL gulf coast Wed morning and continues to push increased moisture in across south and central GA through Thursday. This wave/potential tropical system is expected to interact with stalled frontal boundary which could lead to a significant amount of precipitation moving into the area by mid to late week. This is also supported by the models showing Precipitable water values increasing across central GA Wed/Thu into the 1.5" to 1.9" range. Instability indices also increase but not to substantially so mainly looking for this to be a heavy rain event. Things clear out for friday as that digging upper level trough finally pushes things eastward allowing a much drier airmass to move into the region. 01 AVIATION... 12Z Update... VFR conditions are expected to persist through the TAF period, with no precipitation currently forecast and a FEW-SCT cu field at around 050 developing by mid-afternoon. Winds will be 6 kts or less, mainly from SE today before shifting to SW after 06Z Sunday morning. //ATL Confidence...12Z Update... High confidence on all elements. King && .PRELIMINARY POINT TEMPS/POPS... Athens 86 62 88 68 / 0 0 5 5 Atlanta 86 64 88 68 / 0 0 5 10 Blairsville 81 59 81 63 / 0 0 20 30 Cartersville 86 62 87 68 / 0 0 20 20 Columbus 87 64 90 69 / 0 0 5 5 Gainesville 84 63 85 68 / 0 0 10 20 Macon 88 61 90 67 / 0 0 5 0 Rome 88 62 88 69 / 0 0 20 30 Peachtree City 87 61 88 66 / 0 0 5 10 Vidalia 88 65 90 69 / 0 0 5 0 && .FFC WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SHORT TERM...28 LONG TERM....Morgan AVIATION...28