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FXUS62 KFFC 141047 AFDFFC

Area Forecast Discussion National Weather Service Peachtree City GA 647 AM EDT Tue May 14 2024


New 12Z Aviation Discussion

SHORT TERM
(Today through Wednesday)
Issued at 406 AM EDT Tue May 14 2024

Key Messages:

- A couple of strong or severe storms could develop between 4 PM and 10 PM today, especially in central Georgia.

- Scattered sub severe storms are possible in northern Georgia Wednesday afternoon.

Today and Wednesday:

An upper level trough moving at a snails pace through the Tennessee Valley will be the primary player in our weather over the next 36 hours. Southerly flow ahead of the trough will continue to advect moisture northward, allowing low clouds, haze and light rain showers to continue in the region this morning. Later this afternoon it will draw a warm front northward into central Georgia. This front should serve as a focal point for thunderstorms between 4 PM and 10 PM.
Though additional elevated thunderstorms may form north of the warm front in northern Georgia. Diurnal heating and rising surface dewpoints (peaking near 70 degrees) behind the warm front should allow SBCAPE values to peak in the 1000 to 2000 J/kg range this afternoon. This instability should be coupled with adequate shear values (0 to 6 km values between 25 and 40 kt) for isolated supercell development near the warm front. Note the mean STP values in the 1 to 3 range in the 00Z HRRR guidance. Mid level lapse rates have also improved in the CAM guidance compared to what was projected yesterday (mean values are now in the 6.0 to 7.0 C/km range). Given these considerations today's Marginal Risk (Level 1 of 5) appears to be a higher end Marginal. This is especially true along a line from Columbus to Macon to Augusta, where proximity to the warm front will elevate the severe potential. Along this line damaging winds are the main concern, but large hail or a brief tornado are possible. Further north the elevated nature of the storms should lead to a lower potential for damaging winds or hail.

Patchy fog could occur tonight along and north of Interstate 20. Any fog should dissipate quickly Wednesday morning as a weak cold front pushes through the state. Diurnal heating and proximity to the core of the upper level trough should promote scattered showers and thunderstorms over the terrain of northern Georgia Wednesday afternoon and evening. Weak shear (0-6 km values between 10 and 20 kt) and limited instability (500-1000 J/kg) should generally keep these storms sub severe. A couple isolated showers or storms could occur over central Georgia, but narrow CAPE profiles, weak mid level capping and lower surface dewpoints should limit the potential. More sunshine should allow temperatures to increase Tuesday (compared to today) despite the passage of a cold front in the morning. Look for afternoon highs in the upper 70s in northern Georgia and lower 80s in central Georgia.

Albright

LONG TERM
(Wednesday night through Monday)
Issued at 406 AM EDT Tue May 14 2024

Long term picks up Wednesday evening/overnight, where some lingering showers and isolated thunderstorms may be ongoing across northern GA, but should quickly come to an end. Thursday continues to look dry as it has all week, with rain beginning to spread into the area Friday morning into the day. There is some signs of complications for rain spreading in - ensembles are showing slower solutions yet again tonight, with 00Z guidance pushing best probabilities into later Friday evening and into the day on Saturday. Deterministic guidance provides some insight into what seems to be happening - models seem to like keeping the upper level low moving across the south mostly detached from the northern branch of the jet, allowing it to continue to slowly lumber its way across the region into Saturday. Another potential complication to precipitation chances would be convective evolution on the previous day into Friday afternoon, similar to what we've seen play out with events yesterday (Monday), where a strong MCS cuts off the Gulf and prevents much of the potential rainfall from impacting the area.
This seems plausible given that the current system has pushed the theta-e gradient well into the Gulf and the developing sfc low that will drive Friday and Saturday's rainfall won't be anything spectacular. The mass response to the sfc low will be modest as a result, so we certainly won't see that theta-e gradient lift rapidly, and it is likely to be somewhat reinforced by some isentropic lift to the north of it. That gradient would likely be the focus of an organized convective system. All this rambling is to say that uncertainty still remains regarding overall rainfall and storm chances on Friday and Saturday, and while current rainfall amounts are in the 1-2" range, there is a large range of what may occur that will be highly dependent on several critical points this forecaster doesn't trust the models to handle well.

After that, there is decent signal in the ensembles that the upper level low will slip to the SE, allowing for a sfc low to form off the GA/Carolina coastlines. This could throw back some cloud cover and moisture on Sunday which will need to be monitored, but currently keeping low end PoPs in the forecast to account for uncertainty. Low off the coast could also create some sudo-wedge conditions that would impact temps across parts of GA, but too much uncertainty again to really deviate from the NBM guidance on this.

Lusk

AVIATION
(12Z TAFS)
Issued at 642 AM EDT Tue May 14 2024

A mix of LIFR, IFR and MVFR conditions (ceilings 300 to 1500 ft AGL and visibilities of 2 to 6 SM) will continue through 15Z Tuesday, then the majority of the region should gradually shift towards MVFR conditions (ceilings 1000 to 3500 ft AGL). Rain showers will continue in northern and central Georgia through 06Z Wednesday, then any rain should become focused in far northern Georgia. Scattered thunderstorms are possible from 20Z today through 06Z Wednesday. Southeast winds (2 to 8 kt) will continue through 15Z, then southwest winds (6 to 14 kt) will develop, especially over central Georgia. Wind gusts in the 20 to 30 kt range could (20% chance) occur at KMCN or KCSG.

//ATL Confidence
12Z Update
Moderate confidence in the ATL TAF overall.
Moderate confidence in the ceiling, wind, visibility and precipitation forecasts.
Low confidence in the thunderstorms forecast.

Albright

PRELIMINARY POINT TEMPS/POPS
Athens 62 80 60 86 / 60 30 0 0 Atlanta 63 79 62 85 / 50 20 0 0 Blairsville 58 72 57 79 / 70 60 10 0 Cartersville 60 79 59 84 / 50 30 0 0 Columbus 65 83 62 88 / 60 0 0 0 Gainesville 63 77 62 84 / 40 40 0 0 Macon 65 83 62 87 / 60 10 0 0 Rome 61 80 59 85 / 60 30 0 0 Peachtree City 62 80 60 86 / 60 10 0 0 Vidalia 68 86 66 87 / 30 10 0 0

FFC WATCHES/WARNINGS/ADVISORIES
None.

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