078 FXUS62 KFFC 161845 AFDFFC Area Forecast Discussion National Weather Service Peachtree City GA 245 PM EDT Thu May 16 2024 ...Afternoon Area Forecast Discussion... .SHORT TERM... (This afternoon through Friday) Issued at 237 PM EDT Thu May 16 2024 A transient upper-level ridge and associated surface high pressure are producing dry, warm, mostly sunny conditions this afternoon. Temperatures are on track to top out in the mid-80s to upper 80s outside of the mountains. Scattered to widespread showers are expected to move in from west to east tomorrow (Friday) morning as a shortwave trough and associated upper-level speed max approach from the west. Showers and ample cloud cover in the morning and afternoon will likely preclude deep convection during the day, but depending on the progression of convective clusters/an MCS upstream over MS and AL, portions of the CWA could have convection to contend with overnight. SREF has a 25% to 45% chance of Supercell Composite Parameter (SCP) greater than 5 across much of the CWA from 00z to 06z Saturday, which indicates the co-location of ample shear and ample instability. The primary hazard will be damaging wind gusts with secondary, less-probable hazards of large hail (1" in diameter or larger) and tornadoes. At this time, SPC has much of central GA outlooked in a Marginal Risk with the far southwestern portion of the CWA (including Columbus and Americus) in a Slight Risk. All this said, the severe weather potential is conditional, as an equally reasonable scenario is that showers during the day tomorrow will stabilize the environment and produce a cold pool, which could encourage upstream convection over MS and AL to weaken and/or migrate southeastward along the cold pool boundary. The CAMs are all over the place in their handling of precip Friday into Saturday. In addition to the conditional threat for severe weather, WPC has an area encompassing western GA and the Atlanta metro outlooked in a Slight Risk for excessive rainfall. The current expectation is that the potential for heavy rain will peak during the afternoon and evening hours on Friday as the chance for deep convection and/or training increases while PWAT is progged to reach 1.5" to 1.8". Additionally, soils across much of the area under the Slight Risk are quite saturated from recent rainfall, which could set the stage for increased runoff. The potential for heavy rain will carry over into the start of long term period, so the forecasted rainfall totals are covered in said discussion below. Martin && .LONG TERM... (Saturday morning through next Wednesday) Issued at 237 PM EDT Thu May 16 2024 Looking into the longterm forecast, specifically Saturday, conditions will be heavily dependent on short term outcomes with the MCS path and subsequent destabilization potential. Continued shear and lifting support along the warm front, and with the slowly approaching shortwave, will mean that any CAPE that does develop will be readily accessed. We will need to watch closely for a continued severe threat of damaging winds and hail, although a brief tornado may not be out of the question. Should we get cut off from the warm and moist air to the south, conditions will likely behave for the most part. In either scenario, flooding may become a concern given the potential deep moisture (PWATs>1.8") and storm motion/flow parallel to the front through Saturday evening. Current model guidance already indicates vorticity streamers along the front which drive efficient precipitation training over small areas. While the heaviest rains should stick over AL, highly localized values of 4+" (Friday through Saturday afternoon) are possible. Precipitation outside of concentrated thunderstorm training will likely see closer to 2 to 3 inches. Should GA become cutoff from the warm and moist flow, the potential for localized values of 4+" will be greatly diminished but not outright removed. Conditions begin to dry out Sunday with a few remnant showers lingering on the backside of the low. As the low moves offshore, NE flow begins to dominate and drier air starts to move in. Models continue to indicate some minor cyclogenesis with the low as it moves off the East Coast. This will reinforce NE flow and set much of North and East Central GA in a pseudo wedge pattern on Monday. Cloudy conditions and a few sprinkles may be possible with this through mid next week. The main effect will be felt with the temperatures which have continued in a downward trend over the last several model runs. Model uncertainty remains elevated with this scenario (with a model spread of ~15 degrees for some areas), so will likely continue a blend of the previous forecast temperatures with continued drop in Monday's highs. Temperatures through mid next week will continue to warm, sending highs into the mid 80s and near 90. Small precipitation chances return for mostly north GA on Wednesday and into Thursday morning. SM && .AVIATION... (18Z TAFS) Issued at 127 PM EDT Thu May 16 2024 Expect the Cu field to produce FEW/SCT 030-050 cloud bases through the afternoon. Gradually lowering CIGs will move in from the W overnight thru tomorrow (Friday) morning. Current thinking is that all sites except for AHN and MCN will see MVFR CIGs by late morning as -SHRA move in, and that MVFR will persist thru much of the day. Have introduced a PROB30 from 18z-00z tomorrow for -TSRA at ATL, but confidence is relatively low given the anticipated OVC mid-level cloud deck hampering destabilization. Winds will be WNW to NNW this afternoon and will become LGT to calm overnight. Tomorrow, winds will generally be SSE, but could occasionally teeter over to SSW. //ATL Confidence...18Z Update... Medium to high confidence on all elements. Martin && .PRELIMINARY POINT TEMPS/POPS... Athens 62 76 65 79 / 0 70 80 90 Atlanta 66 75 68 78 / 10 80 80 90 Blairsville 58 71 61 74 / 10 80 80 90 Cartersville 62 74 65 79 / 10 80 80 90 Columbus 67 80 71 79 / 20 70 80 90 Gainesville 63 73 65 76 / 0 80 80 90 Macon 64 80 70 81 / 0 70 70 90 Rome 62 74 66 80 / 20 80 80 80 Peachtree City 63 76 67 78 / 10 80 80 90 Vidalia 67 85 72 87 / 0 30 50 90 && .FFC WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Martin LONG TERM....SM AVIATION...Martin