textproduct: Columbia

WHAT HAS CHANGED

Widespread showers and storms are developing in the CSRA and will continue to push into the Midlands this afternoon and evening. Aviation discussion updated for 18z TAF.

KEY MESSAGES

- 1. Widespread thunderstorms, a few of which may become strong to severe, and localized flash flooding through tonight.

- 2. Shower and thunderstorm chances continue through the upcoming week.

DISCUSSION

Key Message 1: Widespread thunderstorms, a few of which may become strong to severe, and localized flash flooding through tonight.

Latest mesoanalysis indicates significant surface destabilization in the CSRA with sbCAPE exceeding 2500 J/kg. There remains a sharp gradient in instability associated with a wedge front in place in the northernmost portion of the forecast area leading to a notable temperature gradient as temperatures will generally be in the low 70s in the north/northwestern area to mid to upper 80s southeast. A shortwave moving through Georgia will continue to shift eastward which with plentiful instability leading to widespread storms continuing to increase in coverage through the rest of the afternoon. With PWATs around 1.8 to 1.9 inches, near the 99th percentile for this time of year and wet bulb zero heights around 13,000 feet, rainfall will be efficient. With areas north of I-20 receiving substantial rainfall yesterday, generally 2-4 inches based on CoCoRaHS and radar estimates, any training storms could cause localized flash flooding. Widespread severe weather is not expected as CAPE profiles are generally skinnier, with limited mid-level lapse rates. With increasing low level lapse rates, however, could see localized strong to potentially severe precip-loaded downdrafts develop. With forcing provided by the shortwave, convection will likely linger into tonight, although any severe threat will be limited.

Key Message 2: Shower and thunderstorm chances continue through the upcoming week.

Southwest flow persists over the area with a ridge offshore over the western Atlantic and deep troughing strengthening over the Gulf coast, ensuring a strong moisture source from the Gulf of America. PWATs will remain well above average with NAEFS mean indicating they will stay above the 90th percentile. There will several shortwaves pushing through the southwest flow with moderate destabilization expected each day. This will lead to an unsettled period with showers and thunderstorms likely developing each afternoon persisting into the evening. While the severe threat will be generally low, will continue to need to monitor a potential localized flash flooding threat, especially in the northwestern area which is most likely to be the location where shortwaves will push through the area and which has already received substantial rain so far this weekend.

AVIATION /18Z SATURDAY THROUGH THURSDAY/

Mix of MVFR and VFR ceilings this afternoon with showers and storms possible. Rain chance diminish some tonight, but more restrictions are expected.

As better mixing is occurring ceilings have generally lifted, but a mix of MVFR and VFR cigs remains across the TAF sites with bountiful low level moisture in place. A stalled front sits across the central Midlands so south of this boundary, light winds are more southeasterly, and north of this, winds a more easterly to northeasterly. Showers and storms are starting to fire across the region as well, though coverage is fairly scattered. Due to this, chances exist at each terminal through this evening to see restrictions from convection where gusty winds could be possible in any stronger storms. Majority of this activity is expected to begin diminishing between 23z-02z, but some showers and weaker storms may linger into the overnight period. A PROB30 group has been added after 00z to account for this. Guidance remains fairly aggressive in another round of cig restrictions that could move in as early as 23- 02z. Ceilings are expected to drop to MVFR during that time, before falling further to IFR late tonight into early Sunday morning. Patches of LIFR cigs will be possible as well. Restrictions are expected to linger through the end of the TAF period, but improvement is expected late Sunday morning into the afternoon toward MVFR. Another round of showers/storms will be possible just after this TAF period.

EXTENDED AVIATION OUTLOOK...Abundant low level moisture will bring more rounds of morning restrictions from fog/stratus to finish the weekend and to start the next work week. Scattered afternoon showers and storms are possible each day into the middle of next week.

CAE WATCHES/WARNINGS/ADVISORIES

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