Area Forecast Discussion
Issued by NWS Atlanta, GA
Issued by NWS Atlanta, GA
Versions:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
101 FXUS62 KFFC 170607 AFDFFC Area Forecast Discussion National Weather Service Peachtree City GA 207 AM EDT Fri May 17 2024 ...New 06Z Aviation 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 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... (06Z TAFS) Issued at 206 AM EDT Fri May 17 2024 High clouds will continue to spread from west to east across the forecast area over the next few hours. Ceilings will gradually lower through the morning hours, down to 8-10 kft by 10-12Z and further to MVFR by 15Z. Showers are forecast to spread into the area this morning, with scattered showers moving into ATL by 12Z and becoming more widespread around by 15Z. Chances for thunderstorms appear to be greatest this afternoon with forcing from a disturbance aloft combined with diurnal instability. As such, a PROB30 for TSRA has been maintained from 18-00Z at all sites. Winds will be light, at 4 kts or less, and variable to start the period, coming up from E to SE at 4-8 kts after sunrise. Winds may briefly shift to SW this afternoon in portions of central Georgia. Ceilings are forecast to lower to IFR after 00Z at the northern TAF sites. //ATL Confidence...06Z Update... Medium confidence on the timing of ceiling lowering and precip onset. High confidence on all other elements. King && .PRELIMINARY POINT TEMPS/POPS... Athens 65 79 63 81 / 80 90 50 60 Atlanta 68 78 65 81 / 80 90 50 40 Blairsville 61 74 59 76 / 80 90 50 60 Cartersville 65 79 62 81 / 80 90 50 40 Columbus 71 79 66 84 / 80 90 50 30 Gainesville 65 76 64 80 / 80 90 50 60 Macon 70 81 66 84 / 70 90 50 50 Rome 66 80 62 84 / 80 80 50 40 Peachtree City 67 78 64 82 / 80 90 50 40 Vidalia 72 87 69 84 / 50 90 70 60 && .FFC WATCHES/WARNINGS/ADVISORIES... None. && $$ SHORT TERM...Martin LONG TERM....SM AVIATION...King