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FXUS62 KFFC 092339 AFDFFC

Area Forecast Discussion National Weather Service Peachtree City GA 639 PM EST Sat Dec 9 2023

New 00Z Aviation Discussion

SHORT TERM
(This afternoon through Sunday)
Issued at 143 PM EST Sat Dec 9 2023

Primary forecast concerns in the short term period are likelihood and timing of strong/severe storms and heavy rain tonight and potential for very light snow accumulations at elevations above 3000ft in NE GA Sunday evening.

Early batch of scattered SHRA associated with warm advection moved off this morning, while mid 60s dewpoints advecting north into NW AL with clearing skies this afternoon leading to favorable environment for a few severe storms and tornadoes. Line of convection expected to approach NW GA around midnight but could see small, fast-moving supercells ahead of the line as supported by a few CAMs including recent HRRR runs. SBCAPE as high 1000 J/kg as convection moves into the state but wanes overnight to no more than 500 J/kg by 12Z, mostly in a thin "ribbon" ahead of the convective line with greater values towards westcentral GA and SE AL. 0-1km SRH and 0-3km line-normal shear should be sufficient for a few mesovortices and brief/weak tornadoes within QLCS, which is also supported by a few CAMs in 2-5km Updraft Helicity fields, even as late as 10-12Z. After 12Z, low level shear decreases and isolated tornado and wind threat decreases with it. Could see very brief, strong/severe storm with damaging winds along the line before they move out of the CWA in the mid afternoon.

Rainfall totals through Sunday expected to remain under 2 inches, with a little more expected in the NE GA mountains. Rainfall rates should be low enough and FF guidance sufficient to preclude any flash flooding but will need to be monitored even with ongoing long term drought conditions.

Front running about 6 hours behind the convective line with steady/falling temps strong NW winds gusting to 25-30 mph, just below wind advisory levels. Small chance for snow mixing in with light rain at higher elevations in NE GA Sunday evening, though cold advection will be very strong. At elevations above 3000 ft, could see < 1/2 inch accumulation on grassy surfaces by 06Z Monday morning. Not enough confidence in this and no impacts expected even if it does occur, so no plans to issue any kind of Winter or Special Weather Statement. That said, model trends have been consistent showing temps falling rapidly and going just below freezing as the moisture and light showers move out. Often CAA pushes precip out in this pattern but orographic lift might squeeze out a surprise 1/2 inch somewhere.

SNELSON

LONG TERM
(Monday morning through next Friday)
Issued at 143 PM EST Sat Dec 9 2023

Key Messages:

- Dry weather is forecast in Georgia through Friday.

- Morning low temperatures should dip into the 20s along and north of Interstate 85 Monday and Tuesday.

- Rain chances return to the region next weekend.

Monday through Wednesday:

Zonal flow aloft and surface high pressure should keep our weather dry during this period. The fair weather conditions will be favorable for chilly overnight temperatures. This will be especially true on Monday and Tuesday mornings when limited cloud cover, light winds, and low humidity should allow morning lows to dip into the 20s along and north of Interstate 85. With a relatively dry airmass in place, afternoon high temperatures should recover fairly well each day. Highs in the upper 40s and lower 50s on Monday should trend towards upper 50s on Wednesday.

It continues to look like low relative humidity values (30-35%)
could have us flirting with near critical fire danger conditions in the north Georgia mountains Monday, Tuesday and Wednesday afternoons. The deciding factor may be how fuels respond to this weekends rainfall. For now it looks like there is a roughly a 25% chance of us issuing a Fire Danger Statement for the region each afternoon.

Thursday and Friday:

The majority of the GEFS and EPS ensemble members favor weak upper level ridging in our region during this period. With this in mind our forecast remains dry for both Thursday and Friday. Overall confidence in the precipitation forecast is lowest for Friday and Friday night due to timing uncertainties with the next potential trough as it moves east from Texas and/or the Gulf of Mexico.

Over the last 24 hours our temperature forecast has trended downward slightly for this period. We now expect afternoon highs to be near seasonal averages (low to mid 50s). This trend has shown up in both the EPS and GEFS guidance and is linked to the strength of a surface high (cooler airmass) shifting east from the Central Plains. Spreads in the NBM high temperature guidance (25th to 75th percentiles)
remain large for this period as well, generally around 10 degrees.

The Outlook for Next Weekend:

Ensemble guidance leans towards weak troughing in the region next weekend. Due to this rain chances (20 to 40%) creep back into the NBM and subsequently our forecast Saturday and Sunday. At this time around 75% over the GEFS and EPS members have some accumulating precipitation in our region next weekend.

Albright

AVIATION
(00Z TAFS)
Issued at 634 PM EST Sat Dec 9 2023

Light shra around ATL this evening, but precip should become more widespread. Stronger storms to the SW should weaken and bypass ATL just to the SE in the next hour or two. Precip will become widespread overnight with a line of thunderstorms possible between 08-12Z. Models have slightly slowed the line down so extended the tempo by an hour. SHRA likely on the backside of the front, but think models are having a hard time resolving coverage. Gusty NW winds behind the front. IFR

//ATL Confidence
00Z Update
Med confidence all elements.
NListemaa

PRELIMINARY POINT TEMPS/POPS
Athens 59 64 31 52 / 80 100 50 0 Atlanta 60 62 32 48 / 100 100 10 0 Blairsville 53 55 26 44 / 100 80 30 0 Cartersville 55 59 28 49 / 100 70 10 0 Columbus 62 65 33 53 / 80 100 10 0 Gainesville 55 60 32 50 / 100 90 20 0 Macon 61 67 33 53 / 40 100 50 0 Rome 53 58 28 51 / 100 70 10 0 Peachtree City 59 61 29 50 / 90 100 10 0 Vidalia 62 72 36 54 / 20 100 70 0

FFC WATCHES/WARNINGS/ADVISORIES
None.

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