textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 00z TAFs.

KEY MESSAGES

- 1. Unsettled weather returns for the rest of the work week with periods of heavy rainfall possible late this week.

DISCUSSION

Key Message 1: Unsettled weather returns for the rest of the work week with periods of heavy rainfall possible late this week. Broad toughing remains across the eastern CONUS as a 90-100 kt upper jet streak traverses the lower Tennessee Valley. This has lead to an area of upper diffluence/divergence across the Southeast with scattered rain showers extending from the western/southern FA back to the west across GA into southern AL.

As PWAT's continue to raise slightly toward 1.90-2.0" and upper forcing from the jet streak remains in place overtop the stalled surface front, isolated to scattered showers will remain possible this evening and overnight, where efficient rainfall is possible as showers possibly train over the FA. The overall flash flood risk is low, but a couple spots of nuisance flooding cannot be ruled out if training occurs over a couple hours late tonight. The upper jet is expected to exit the region early Wednesday as weak 500mb height rises are seen, bringing slightly drier conditions with the best chance for afternoon showers/storms near the far southeastern Midlands and CSRA.

There has not been a significant change to the outlook for the late week and into this weekend, but the potential for heavy rainfall mainly late Thursday through Friday has increased a bit. As what is now Potential Tropical Cyclone One (PTC One) continues toward the northeast from the northwestern Gulf and moves inland Thursday, its remnant tropical moisture is expected to be picked up in westerly to southwesterly upper flow with a shortwave and surface cold front nearing the FA. As moisture increases, scattered shower and thunderstorm development is possible Thursday afternoon and evening where AI/ML guidance continues to hint a couple strong to marginally severe storms could be possible. Around 59% of the individual members in the LREF cluster analysis show the main plume of moisture with PWAT's that near 2.10-2.40" (140-170% of normal) moving in late Thursday into Friday morning. Forecast soundings during this period are very moist and have warm cloud depths that exceed 13,500 ft with a 30-40 kt LLJ in place, signaling the potential for heavy rainfall during this window. Overall, a fairly complex forecast scenario is expected Thursday afternoon through Friday with the interaction of a surface cold front and remnants of PTC One, but periods of heavy rainfall are possible as well as a marginal risk for severe weather. Slightly drier conditions are favored across ensemble guidance into this weekend.

AVIATION /00Z WEDNESDAY THROUGH SUNDAY/

Restrictions developing tonight along with increasing chances for rain.

MVFR ceilings have moved over AGS, DNL, and AIK prior to the start of the TAF period. Expect these ceilings to be prevailing for the most part, but will likely bounce into VFR at times. CAE, CUB, and OGB are expected to be VFR for the first 2-3 hours of the TAF period before going to MVFR. Ceilings are then expected to lower to IFR around 06z at all sites, then gradually improve after daybreak. Periodic showers can be anticipated at AGS and DNL over the next few hours ahead of more steady rain after 06z. The rain is forecast to spread eastward, but there is question how much of these showers make it to CAE and CUB, so have left VCSH at those terminals. Will amend as needed. Generally southwest winds prevail through the TAF period, staying elevated overnight and becoming breezy after 18z, gusting to 15-20 kts.

EXTENDED AVIATION OUTLOOK...Diurnally favored convection possible each afternoon. Breezy conditions expected Thu/Fri with increased chances of rain as a Gulf coast system approaches the area.

CAE WATCHES/WARNINGS/ADVISORIES

SC...None. GA...None.