Sunrise 6:34 AM   Sunset 8:30 PM Moonrise 9:18 AM   Moonset 12:00 AM

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FXUS62 KFFC 121623 AFDFFC

Area Forecast Discussion National Weather Service Peachtree City GA 1223 PM EDT Sun May 12 2024

UPDATE
Issued at 1221 PM EDT Sun May 12 2024

Forecast is on track, and no update is planned. /SEC

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
(12Z TAFS)
Issued at 616 AM EDT Sun May 12 2024

VFR conditions (FEW-BKN AOA 10000 ft AGL and unrestricted visibility) will linger in the region through at least 09Z Monday, then areas of IFR or MVFR (800 to 3000 ft AGL) may mix in over western Georgia. Scattered light showers should develop after 09Z Monday and linger through at least 18Z Monday. Northwest winds (3 to 9 kt) will continue through 01Z Monday, then winds will be light and variable.

//ATL Confidence
12Z Update
Overall confidence in the KATL TAF is high. High confidence in the wind and visibility forecasts. Moderate confidence in the precipitation forecast and ceiling heights after 09Z Monday.

Albright

PRELIMINARY POINT TEMPS/POPS
Athens 56 73 60 75 / 0 70 90 90 Atlanta 60 70 62 77 / 10 70 90 90 Blairsville 52 68 56 70 / 0 60 90 100 Cartersville 57 71 60 77 / 10 80 90 90 Columbus 63 76 66 80 / 30 70 80 90 Gainesville 57 70 61 73 / 0 60 90 90 Macon 61 75 64 78 / 20 70 90 100 Rome 57 71 62 78 / 10 70 80 90 Peachtree City 59 71 62 79 / 20 80 90 90 Vidalia 64 80 67 80 / 10 60 80 100

FFC WATCHES/WARNINGS/ADVISORIES
None.

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