textproduct: Columbia

WHAT HAS CHANGED

Removed tonight wording from Key Message 1 and made other minor changes. Updated aviation discussion for 12z 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.

At daybreak, showers and thunderstorms are starting to enter the state from the west. Model guidance has not handled their dissipation well and there has been recent development across northern Georgia. With this in mind, PoPs were increased and thunder was added to the grids. Given the time of day and lack of instability, severe weather is not expected but the stronger cells may produce gusty winds and briefly heavy rainfall as the move through the FA.

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 /10Z TUESDAY THROUGH SATURDAY/

Patchy MVFR ceilings are seen this morning as a decaying line of convection approaches later this morning. Another round of restrictions possible early Wednesday.

A stratus deck has worked into AGS/DNL/AIK over the last couple hours and is slowly drifting toward the north. This is bringing MVFR ceilings that may be intermittent for the next 3-5 hours across the area with light and variable winds. While the line of convection previously in the Tennessee Valley continues to wane, some scattered showers/storms ahead of the main line have formed across AL/GA, and should push near the Augusta and Columbia terminals between 13-15z. The main line of convection should continue to be on a downtrend through the morning, but confidence has increased in showers near the TAF sites so have added a TEMPO group through 17-18z for this activity. A rumble or two of thunder cannot fully be ruled out with this activity. This afternoon, winds pick up around 6-8 kts out of the southwest with VFR conditions prevailing, though mid to high clouds likely remain in place much of the day. Tonight, light and variable winds eventually become a bit more southerly as another batch of rain nears the FA at the end of the TAF period. There is increasing confidence in potential ceiling restrictions into Wednesday morning with this activity and thus at least MVFR ceilings are expected, but guidance is hinting IFR conditions could be possible.

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.