Area Forecast Discussion
Issued by NWS Atlanta, GA
Issued by NWS Atlanta, GA
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850 FXUS62 KFFC 120745 AFDFFC Area Forecast Discussion National Weather Service Peachtree City GA 345 AM EDT Sun May 12 2024 ...Morning Area Forecast Discussion... .SHORT TERM... (Today through Monday) Issued at 345 AM EDT Sun May 12 2024 Key Messages: - Fair weather will prevail in the region today. - Cloudy skies, cooler temperatures and scattered light rain showers are expected Monday. Today & Monday: Upper level ridging and a surface high will bring benign weather to the region today. The core of the surface high will be closer to us today (compared to Saturday) and this will result in lighter winds this afternoon. Northwest winds between 4 and 8 mph can be expected. Light and variable winds will develop tonight as the boundary layer decouples and the surface high settles over Georgia. An approaching trough will bring significant changes to Georgia`s weather on Monday. Cloud cover will return in force tonight as southwesterly follow in the mid and upper levels brings a surge of moisture northward. By Monday morning isentropic lift associated with a weak mid level trough (ahead of the larger shortwave in the Plains) could produce light rain showers. Any accumulations through Monday morning should be less than 0.25 inches. A relative minimum in precipitation potential is expected Monday afternoon before widespread rain showers and thunderstorm build back in Monday evening/night (associated with lift from the parent trough and a low level jet). Shifts in the forecast towards greater rain chances and more cloud cover have introduced a significant amount of uncertainty into the high temperature forecast for Monday afternoon. Below average high temperatures are likely (>90% chance), but the spread in the NBM guidance is quite large. For the Atlanta area the spread between the 25th and 75th percentile MaxT`s is 7 degrees (69 to 76 degrees). Similar large spreads exist for the rest of northern and central Georgia. Our deterministic forecast remains close the the 50 percentile of the NBM and favors a highs in the lower 70s for most of northern and central Georgia. Albright && .LONG TERM... (Monday night through Saturday) Issued at 345 AM EDT Sun May 12 2024 The long term forecast looks quite wet overall with a parade of lows within the southern branch of the jet moving past the CWA through the end of the week (and possibly even into early next week, but that is beyond the scope of this forecast). The forecast picks up Monday night with rain likely ongoing across the CWA. Upper level cut off low with begin to progress eastward, albeit slowly, and initial upper level divergence will have overspread the CWA. Isentropic lift over a theta-e gradient should provide for widespread rain showers through the night, though some elevated instability may provide for a few rumbles of thunder. As the low progresses east, but upper level support will arrive with moderate jet streak overspreading the CWA on Tuesday. Ensemble guidance paints a decent probability space for the intersection of instability, shear, and precipitation over the CWA, with highest probabilities in central GA, decreasing as you move into north GA. This feels appropriate, and the northward extent may be overdone overall. Models will typically struggle with the rain based reinforcement of the surface boundary attempting to lift north as a mass response to the surface low, and generally these boundaries will remain further south than forecast. In simpler terms, the further south the surface based warm, moist air from the Gulf remains, the lower the overall severe threat for our area. Looking at hodographs and overall model forecast soundings, primary threat would likely be wind and maybe hail. SW surface winds will make ingestion of streamwise vorticity a bit more challenging, keeping tornado threat low for now. Better examination will be had in the short term guidance as Tuesday evening comes into range. The trade off of a lower severe threat may be an elevated flooding/flash flooding risk, especially if that boundary sits in the same location further south and provides a source for repeated lifting of air parcels. Central Georgia would once again be the primary candidate for this, though the sandy soils can take a bit more rain before it becomes a problem. Current forecast QPF over this time period is 2- 4" with locally higher amounts in central GA, and 1-2" across north GA including metro Atlanta. 6 hr flash flood guidance is generally 4" or higher across much of central GA, so any threat may be driven by more convective elements and/or training of cells over the area. The system clears out through Wednesday morning, and we should see some clearing through Thursday before the next system approaches the area. Model trends seem to be slowing this system a bit, pushing the overall timing of rain into Friday. This is another slower moving system, and both the GEFS and EPS probabilities of rain are relatively high through the weekend. Details of what exactly this looks like are bit more fuzzy, though the deterministic suite shows a stalled boundary over the CWA that appears to be the focus of most of the rainfall. This is a bit of a concerning signal given we may have some heavier rainfall on the front end of the week, but certainly too early with too much uncertainty to ring any flooding alarm bells just yet. Lusk && .AVIATION... (06Z TAFS) Issued at 210 AM EDT Sun May 12 2024 VFR conditions (SKC to SCT AOA 5000 ft AGL and unrestricted visibility) should prevail through 06Z Monday, then MVFR/IFR conditions (ceilings between 600 an 2000 ft AGL) may mix in over western Georgia. Scattered showers could occur after 06Z Monday. Light northwest winds (2 to 8 kt) are expected through 01Z Monday, after which point light and variable (0 to 3 kt) winds should prevail. //ATL Confidence...06Z Update... Overall confidence in the KATL TAF is high for all elements. Albright && .PRELIMINARY POINT TEMPS/POPS... Athens 80 56 73 60 / 0 0 70 90 Atlanta 80 60 70 62 / 0 10 70 90 Blairsville 74 52 68 56 / 0 0 60 90 Cartersville 79 57 71 60 / 0 10 80 90 Columbus 82 63 76 66 / 10 30 70 80 Gainesville 79 57 70 61 / 0 0 60 90 Macon 82 61 75 64 / 10 20 70 90 Rome 80 57 71 62 / 0 10 70 80 Peachtree City 80 59 71 62 / 0 20 80 90 Vidalia 83 64 80 67 / 10 10 60 80 && .FFC WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Albright LONG TERM....Lusk AVIATION...Albright