Sunrise 6:58 AM   Sunset 8:10 PM Moonrise 2:30 PM   Moonset 3:37 AM

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FXUS62 KFFC 181426 AFDFFC

Area Forecast Discussion National Weather Service Peachtree City GA 1026 AM EDT Thu Apr 18 2024

UPDATE
Issued at 1013 AM EDT Thu Apr 18 2024

High pressure and mostly dry conditions will persist through the mid afternoon. Models are struggling with the pattern in place and not handling any shortwaves within the zonal flow very well.
The 12Z HRRR didn't initialize the convection currently firing across north central LA. The 13Z HRRR has initialized the convection, but kills it as it moves eastward, firing up a second round later in the afternoon/early evening. Not confident that the first round of convection will diminish, and current radar/satellite trends show no sign of weakening. There is some decent cloud cover out ahead of the activity but there are some big breaks in the clouds. The convection has developed within an axis of higher PWATs and steeper lapse rates. Expect the steeper lapse rates to spread eastward and the PWATs across the CWA to continue creeping upwards through the afternoon.

Since the models haven't initialized the convection out west very well, timing any convection as it approaches the western CWA will be a challenge. Have adjusted pops slightly for now across the western CWA, but will likely have to readjust as the convection out west potentially gets more organized.

SHORT TERM
(Today through Friday)
Issued at 331 AM EDT Thu Apr 18 2024

The line of showers and thunderstorms from yesterday evening has dissipated as the boundary moved into central Georgia. In portions of far northwest Georgia, observations have begun to indicate visibilities of 1/4 SM or less. With winds in this area forecast to remain light (3 mph or less) and relative humidity values forecast to range from 95-100% as cooler air overruns wet soil, dense fog is expected to persist through the early morning hours. As a result, a Dense Fog Advisory has been issued for an area along and west of a line from Paulding to Murray county, and will remain in effect until 10 AM EDT. A weak 500 mb ridge will quickly move across the east- central CONUS today. The subsidence under this ridge will inhibit rain chances through much of the daytime on Thursday and diminish cloud coverage from the northeast this morning into the afternoon.
In spite of this, little change is anticipated in the airmass at the surface. With plenty of sunshine, high temperatures are forecast to rise to 9-14 degrees above climatological normals, into the mid 80s in north Georgia and upper 80s in central Georgia.

As the ridge quickly moves away to the east this afternoon, zonal upper level flow will set up over the region. A shortwave traversing the upper level flow will move through the Ozarks region tonight. A cold front associated with this disturbance will advance towards TN/KY. Hi-res guidance continues to indicate a weakening MCS moving into far north Georgia late tonight into early Friday morning. This MCS is most likely to move from west to east across the far northern tier, with a couple of storms within being capable of producing gusty winds. That said, the motion and evolution of this system will depend on the behavior of the outflow boundary from storms upstream, which makes nailing down the specifics of these MCS systems a challenge.

Low temperatures are anticipated to start Friday morning in the mid 60s across the majority of the area. Increased cloud coverage will inhibit diurnal heating in far north Georgia, where high temperatures will be in the upper 70s to low 80s. Elsewhere across the forecast area, highs will reach into the mid to upper 80s once again. On Friday afternoon, the aforementioned cold front will advance into north Georgia and towards central Georgia, providing a source of lift within a favorable environment for convective activity. At this time, likely PoPs are forecast across the far northern tier with chance PoPs to the south on Friday afternoon.
Considering the warm temperatures and dewpoints in the low to mid 60s, SBCAPE values will climb to between 1500-2000 J/kg in the peak heating hours. Combined with deep layer bulk shear values between 30- 40 kts and steepening low level lapse rates, there is the potential that isolated storms could become strong to severe, capable of producing large hail and damaging wind gusts.

King

LONG TERM
(Friday night through Wednesday)
Issued at 331 AM EDT Thu Apr 18 2024

4/17 LONG TERM

At a glance:

- Isolated to scattered thunderstorms this weekend

- Cooler, drier start to next week behind cold front

Moving into the weekend and the extended range, flow remains quasi- zonal at the mid-levels. The eastward movement of an expansive closed-low rotating over central Canada is progged to send a cold front sweeping across ECONUS, and lingering frontal precipitation is likely to be ongoing across central Georgia on Saturday. Isolated to scattered thunderstorms are possible (especially along and south of I-20) where ensemble guidance gives a 30-50% chance of at least 500 J/kg of SBCAPE. In the absence of dynamic forcing aloft, expecting any storms that form to be fairly run of the mill, producing gusty winds and locally heavy rainfall at times. On Sunday, a weak shortwave impulse will send a stronger slug of moisture across the Deep South, reinvigorating rain chances as it overlaps with our residual frontal forcing. As a result, expect our highest and most widespread chances for showers and thunderstorms to come as we round off the weekend. Even so, rainfall totals across both days are likely to be half of an inch or less.

Any lingering moisture -- and what remains of our front -- will be nudged offshore by a (relatively) stronger shortwave that will dig to the south and east across the Midwest and Ohio River Valley on its way to the Eastern Seaboard. Precipitation chances will be effaced as drier air moves in in the wake of the aforementioned feature, making for a cooler and drier start to next week.

Highs Saturday and Sunday will be governed by how far into the forecast area the front mixes. For now, Saturday's highs will be roughly delineated along I-85: in the 70s to the north, in the 80s to the south (even near 90 in the vicinity of Macon). Sunday will be very cool -- as much as 12 to 16 degrees below average -- especially when compared to the past few days in the 80s: in the upper-50s to 60s north of Columbus and Macon, and in the 70s to the south.
Following the frontal exit, expect our dry airmass to moderate and warm, and highs will eventually reach back into the upper-70s to 80s areawide. Lows will fall into the upper-40s to 50s each day.

96

AVIATION
(12Z TAFS)
Issued at 722 AM EDT Thu Apr 18 2024

Dense fog remains across portions of northwest Georgia, with patchy fog and LIFR ceilings intermittently reaching FTY/RYY for the last few hours. Lower ceilings and visibilities are not expected to reach ATL at this time. The fog should diminish by 14Z, giving way to VFR conditions across the area. Winds will be fairly light through the period, from 3-6 kts. Winds will be mainly NW this morning, shifting to SW by 17Z and through the afternoon. A weakening complex of SHRA/TSRA could move across north Georgia on Friday morning, although much uncertainty remains with the timing and movement of this system. At this time, a PROB30 for -SHRA has been introduced from 10-14Z at ATL.

//ATL Confidence
12Z Update

Medium confidence on all elements.

King

PRELIMINARY POINT TEMPS/POPS
Athens 63 85 62 84 / 30 30 10 30 Atlanta 65 84 63 81 / 30 40 10 30 Blairsville 58 77 56 74 / 60 70 10 20 Cartersville 63 82 58 78 / 40 50 0 30 Columbus 66 88 65 86 / 20 20 10 40 Gainesville 64 82 61 81 / 40 40 0 30 Macon 65 88 65 87 / 20 20 10 40 Rome 63 83 59 76 / 60 60 10 30 Peachtree City 65 86 62 82 / 20 40 10 40 Vidalia 66 90 67 90 / 10 20 10 40

FFC WATCHES/WARNINGS/ADVISORIES
None.

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