textproduct: Columbia

WHAT HAS CHANGED

Key Message 1 timing updated based on the latest model guidance. Updated aviation discussion for 06z TAFs.

KEY MESSAGES

- 1. Rounds of showers and thunderstorms possible during the mid to late week period.

- 2. Rain chances continue into the weekend.

DISCUSSION

Key Message 1: Rounds of showers and thunderstorms possible during the mid to late week period.

The weather across the forecast area tonight is quiet under clear skies outside of some low clouds sneaking into the southern CSRA. Attention towards daybreak turns to strong to severe thunderstorms currently moving into the Tennessee Valley. Latest model guidance suggests this activity will approach the northwestern FA during the early morning hours. The convection will be decaying and should only consist of a few showers by the time it reaches the Midlands after daybreak. Having said that, these showers could produce some light rainfall accumulations later this morning, mainly north and west of I-20.

Another round of convection is expected to develop well to our west later today, weakening significantly before arriving Tuesday night into Wednesday morning. Some of the guidance seems more aggressive with the thunderstorm chances so opted to maintain a Slight Chance of thunder with this second round of activity. Depending on how this activity develops parts of the FA could see additional rainfall.

A cold front then approaches Wednesday afternoon and evening. As the cold front moves in, moderate wind shear coupled with sufficient instability hints at the potential for low-end storm organization, though this will depend largely on the aforementioned morning convection and whether we can clear out and destabilize the atmosphere prior to the arrival of the cold front. While there severe threat is low, a few thunderstorms could become strong to marginally severe. The Day 3 SPC outlook has a Marginal (1/5) risk for severe weather just to our north so the best risk of severe weather on Wednesday should be across our northern counties.

The unsettled weather may continue for the remainder of the work week with additional rain chances.

Key Message 2: Rain chances continue into the weekend.

Ensemble cluster analysis shows that broad troughing is favored over the eastern half of the US by late week and into the weekend. The NAEFS shows PWAT values approaching the 90th percentile of climatology with IVT near the 97th percentile. This supports a high chance to likely PoPs from Friday night through Saturday with the potential for a low pressure system to move across the Southeast. While there remains a large spread in model guidance for the time period, there is potential to see widespread rainfall for this event. Although we are too far out to get an accurate determination of rain amounts, we should see confidence forecast amounts increase as we move through the week.

AVIATION /06Z TUESDAY THROUGH SATURDAY/

VFR conditions continue, but low chance for restrictions this morning as decaying area of showers enters the FA.

Skies remain mostly clear, but an area of stratus can be seen pushing inland from the coast with high clouds moving in from the west, associated with convection in the Tennessee Valley. Winds are now light and variable as well, but the CAE VAD profile does show around 30 kts of southwesterly flow at 1000 ft. LLWS is not in the TAF at the moment as surface winds are elevated enough, but this is worth mentioning. In terms of possible restrictions tonight, guidance remains fairly "wishy- washy" where periods of MVFR ceilings cannot be ruled out mainly after 08-11z as patches of stratus push northward from the coast and again between 14-17z as decaying showers move into the area. Overall, stratus pushing inland could cause a mix of VFR and of MVFR ceilings before a couple showers could near the TAF sites later in the morning with MVFR ceilings. After this, SCT to BKN mid and high level clouds linger the remainder of the TAF period. Winds remain fairly variable through the morning before becoming more southwesterly around 5-8 kts this afternoon. Winds then become light again this evening and tonight.

EXTENDED AVIATION OUTLOOK...Restrictions will be possible Wednesday morning into the afternoon as a system moves in with rain chances and associated cig/vsby restrictions. Periods of restrictions are possible late this week into the weekend with more rain chances.

CAE WATCHES/WARNINGS/ADVISORIES

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