Area Forecast Discussion
Issued by NWS Columbia, SC
Issued by NWS Columbia, SC
951 FXUS62 KCAE 181857 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 257 PM EDT Fri Sep 18 2026 .WHAT HAS CHANGED... Potential for cold air damming to develop by the middle of next week. Aviation discussion updated for 18z TAFs. && .KEY MESSAGES... - 1. Above average temperatures and increased chances for showers and storms continue into early next week. - 2. Cooler and drier air returns by the middle of next week but forecast uncertainty remains. && .DISCUSSION... KEY MESSAGE 1: Above average temperatures and increased chances for showers and storms continue into early next week. The pattern features an upper ridge centered over TX and an upper low off the northeast coast of FL. As the ridge slides slowly wets, the upper low will retrograde westward into the Gulf this weekend. The result is an increase in moisture across the area due to confluent flow between the high and low. There has been a bit more mid level cloud cover across the area than previously expected, which has slowed warming, and temperatures are sitting in the mid to upper 80s with a few low 90s toward the NC/SC border where there has been more sun. A weak shortwave and surface trough are still expected to force some showers and thunderstorms mainly north of the I-20 corridor this evening. However, the timing should be slightly later due to the lingering cloud cover. A cu field is starting to get organized as of this writing, as seen on visible satellite imagery. A few robust storms are observed across central NC and moving south. Mesoanalysis/RAP forecast does show a bit better environment developing in the next few hours, but the severe threat (mainly damaging winds) still appears to be low. The Marginal Risk (1 of 5) will be limited to the north and western portion of the forecast area, with the threat diminishing quickly with loss of heating. A few CAMS continue convection overnight, but coverage should be decreasing overall. The unsettled pattern will continue into early next week with PWATs holding around 125-150% of normal. While widespread forcing will likely be limited, this deep layer moisture and a unseasonably hot and humid air mass will support scattered showers and storms each afternoon through Tuesday. KEY MESSAGE 2: Cooler and drier air returns by the middle of next week but forecast uncertainty remains. There remains some uncertainty as to the exact pattern that evolves towards the middle of next week, but run to run model consistency is increasing. The aforementioned upper low is progged to eject out of the northeast Gulf and up the Eastern Seaboard Tuesday into Wednesday. This will make way for high pressure strengthening over the northeast and ridging down the coast to potentially set up a cold air damming scenario. However, the classic southwest flow aloft doesn`t appear to set in until late in the week or essentially beyond the scope of this forecast package, and drier air is expected to move in from the northwest. This should limit our rain chances late next week. In the meantime, blended guidance favors near normal temperatures for highs though with large IQRs during this period, with the distributions skewed towards lower values. We will need to continue to monitor trends over the coming days. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... VFR conditions expected through the forecast period outside of possible convection. A broken band of low to mid-level clouds and light showers have persisted south of the I-20 corridor early this afternoon, with RA noted at AGS and DNL in the past hour. Have added VCSH mentions for the next hour at AGS and DNL with ongoing showers and until 20z with light showers approaching OGB. Farther north, convection has begun to initiate convection over the higher terrain and Piedmont of North Carolina early this afternoon. This convection should move southward into through the forecast area later this afternoon through this evening, with CAM guidance mostly depicting this convection along or north of the I-20 corridor. Have maintained PROB30 group convection during the 22z-04z time frame at all terminals except OGB, where confidence is lower. Higher clouds (at or over 10kft) will rebuild overnight across much of the forecast area, which should result in warmer lows tonight and prevent vis restrictions developing. These clouds should lower (around 5kft) into broken to scattered cumulus by early Saturday afternoon. EXTENDED AVIATION OUTLOOK...Chances for showers and storms continue through the weekend. Morning cig/vsby restrictions are possible this weekend as well. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...None. GA...None. && $$ DISCUSSION...EC AVIATION...SF