Area Forecast Discussion
Issued by NWS Atlanta, GA
Issued by NWS Atlanta, GA
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516 FXUS62 KFFC 071900 AFDFFC Area Forecast Discussion National Weather Service Peachtree City GA 300 PM EDT Tue May 7 2024 ...Afternoon Area Forecast Discussion... .SHORT TERM... (This afternoon through Wednesday) Issued at 248 PM EDT Tue May 7 2024 Large 500 mb low is cut off and located over the northern Great Plains becoming increasingly vertically stacked with surface low in same area. This storm system was responsible for the severe weather in the Plains last night, and the organized convection from that has progressed well ahead of a now stalled cold front and mostly fallen apart as it pushes through the eastern CONUS. Some convective debris from that has been traversing the area, and when combined with some AVA aloft from shortwave ridging, has prevented us from taking off convectively this afternoon. This is changing into the evening, and leftover boundary from overnight convection is pushing in, which could provide a focus from some afternoon showers or thunderstorms, though expecting these should be very isolated, with best chances to the north over the higher terrain. Tonight, moisture continues to push into the area. Some convection may push in from the west, dependent on whether or not it can get going over parts of Alabama. North Georgia would be the most likely to see this per hires guidance. There is a small chance some of this could be severe for a brief period in far NW GA, as the parameter space there has decent instability with 40-50 kts of effective bulk shear. A Marginal Risk (1 out of 5) is in effect for far NW GA as a result. With sunset, any convection remaining should become increasingly elevated. Tomorrow, some hires guidance shows some convection taking place across northern GA that should be under severe limits, but may have impacts on overall evolution of convection later in the day. Guidance shows a piece of the upper level low over the Plains breaking towards the eastern CONUS as a potent shortwave, allowing for PVA and decent shear across the CWA Wednesday evening into Wednesday night. Some general afternoon storms will be possible, but the bigger "show" may be later in the night and into early Thursday as a line of storms pushes into northern GA. HRRR and a few other hires members from this morning show very organized convection with some UH tracks. This tracks with the parameter space forecasted - HREF means show MUCAPE of 500-1000+ J/kg still over northern GA by the early morning hours with 30-40 kts of sfc-500 m shear, representative of substantial shear within the low levels. This leads to nearly 100-200 m2/s2 of 0-1 km SRH, which would allow for ingestion of streamwise vorticity for potential updrafts. Want to emphasize however that uncertainty remains in how this will evolve - convective evolution today through tomorrow will have a large influence on the evolution of the upper levels through diabatic forcing and the low levels via outflow and other factors. The environment will be there - it remains to be seen whether any storms will be able to utilize it. Lusk && .LONG TERM... (Thursday morning through next Monday) Issued at 248 PM EDT Tue May 7 2024 Highlights: -Potentially active weather will be ongoing at the start of the long term persisting into Friday. -Drier weather returns by the weekend persisting into early next week. No significant changes with this latest forecast. Still targeting primarily two rounds of severe potential: the first Wednesday night into Thursday morning for North GA (1-20 northward) and the second Thursday evening through early Friday morning for Central Georgia (south of I-20). A low pressure system and attendant cold front will be pushing eastward across the Ohio/TN Valley Regions. This will drive a complex of showers and thunderstorms, ahead of the front, into the northern sections of Georgia Thursday morning. Latest hi-res guidance appears to be slightly quicker with moving this complex into North GA Thursday morning. The primary threat with any strong to severe thunderstorms still appears to be damaging winds as a result of decent deep layer shear and lapse rates accompanying the complex. Hail and possibly an embedded spin-up tornado are still threats as well. This activity will gradually push south through the morning on Thursday and the question remains if the complex will weaken and/or be the focus for possible redevelopment during the afternoon as peak heating occurs. As a reiteration, model guidance typically struggles with the evolution of convective complexes, thus, still accounting for some level of uncertainty as far as exact placement of convective activity beyond Thursday morning. The surface cold front will still be moving through the forecast area and an additional surface low looks to develop across the Lower MS Valley. Latest runs of the 12z hi-res guidance is still picking up on an additional complex of showers and thunderstorms developing and translating eastward towards the area Thursday night into Friday. Again the biggest question will be how this evolves as it progresses towards the area. Lift from the front, decent lapse rates, plenty of wind energy in the mid/upper levels accompanying the main trough may support yet another (third) severe risk late Thursday into Friday for Central Georgia. Damaging winds and hail will be the primary hazards for any strong to severe thunderstorms that develop during the afternoon Thursday or in the evening through the overnight period. Tornado threat is still fairly low at this time. Stay tuned for additional updates... The surface cold front will start to clear the area pushing any lingering rain/thunder chances out of the forecast area by Friday afternoon. We return to NW flow aloft with a brief cool down just in time for the weekend. Some low chance PoPs have been introduced for next week as some mid-level disturbances look to move through flow aloft. 07 && .AVIATION... (18Z TAFS) Issued at 159 PM EDT Tue May 7 2024 VFR to start the TAF period. VFR Cloud cover continues to lift and scatter across most sites this afternoon and will continue into the evening, though some SCT040-060 will remain east and west of ATL. Cigs expected to lower to low MVFR/high IFR tonight across CSG and metro TAF sites, including ATL during morning hours, approx 10Z-14Z. Increasing moisture ahead of next system means BKN cloud cover will likely stick around through afternoon tomorrow. Some isolated storms will be possible by afternoon hours as well. Winds will be SW from 5-10 kts through TAF period. //ATL Confidence...18Z Update...Large 500 mb low is cut off and located over the northern Great Plains becoming increasingly vertically stacked with surface low in same area. This storm system was responsible for the severe weather in the Plains last night, and the organized convection from that has progressed well ahead of a now stalled cold front and mostly fallen apart as it pushes through the eastern CONUS. Some convective debris from that has been traversing the area, and when combined with some AVA aloft from shortwave ridging, has prevented us from taking off convectively this afternoon. This is changing into the evening, and leftover boundary from overnight convection is pushing in, which could provide a focus from some afternoon showers or thunderstorms, though expecting these should be very isolated, with best chances to the north over the higher terrain. Tonight, moisture continues to push into the area. Some convection may push in from the west, dependent on whether or not it can get going over parts of Alabama. North Georgia would be the most likely to see this per hires guidance. There is a small chance some of this could be severe for a brief period in far NW GA, as the parameter space there has decent instability with 40-50 kts of effective bulk shear. A Marginal Risk (1 out of 5) is in effect for far NW GA as a result. With sunset, any convection remaining should become increasingly elevated. Tomorrow, some hires guidance shows some convection taking place across northern GA that should be under severe limits, but may have impacts on overall evolution of convection later in the day. Guidance shows a piece of the upper level low over the Plains breaking towards the eastern CONUS as a potent shortwave, allowing for PVA and decent shear across the CWA Wednesday evening into Wednesday night. Some general afternoon storms will be possible, but the bigger "show" may be later in the night and into early Thursday as a line of storms pushes into northern GA. HRRR and a few other hires members from this morning show very organized convection with some UH tracks. This tracks with the parameter space forecasted - HREF means show MUCAPE of 500-1000+ J/kg still over northern GA by the early morning hours with 30-40 kts of sfc-500 m shear, representative of substantial shear within the low levels. This leads to nearly 100-200 m2/s2 of 0-1 km SRH, which would allow for ingestion of streamwise vorticity for potential updrafts. Want to emphasize however that uncertainty remains in how this will evolve - convective evolution today through tomorrow will have a large influence on the evolution of the upper levels through diabatic forcing and the low levels via outflow and other factors. The environment will be there - it remains to be seen whether any storms will be able to utilize it. Medium-high morning cigs, high all others. Lusk && .PRELIMINARY POINT TEMPS/POPS... Athens 68 88 69 84 / 10 30 40 80 Atlanta 69 87 69 85 / 20 30 50 90 Blairsville 64 82 63 78 / 40 60 80 90 Cartersville 67 87 66 83 / 30 40 60 80 Columbus 70 91 72 89 / 10 20 20 80 Gainesville 69 86 69 82 / 30 50 60 90 Macon 69 90 70 89 / 0 10 10 70 Rome 68 87 67 85 / 40 50 70 90 Peachtree City 69 89 69 86 / 10 20 30 80 Vidalia 69 92 71 92 / 0 10 10 50 && .FFC WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Lusk LONG TERM....07 AVIATION...Lusk