textproduct: Columbia

WHAT HAS CHANGED

Showers and thunderstorms have developed across the forecast area and will continue into this evening. Aviation discussion updated for 18z TAF.

KEY MESSAGES

- 1. Daily shower and thunderstorm chances continue through the week, with isolated flash flooding possible again today.

DISCUSSION

Key Message 1: Daily shower and thunderstorm chances continue through the week, with isolated flash flooding possible again today.

Today/Tonight: Showers and thunderstorms have developed over the forecast area in a strongly unstable air mass. PWATs remain anomalously high, with mesoanalysis above indicating above 2 inch PWATs. Storms have been exhibiting occasionally somewhat strong downdrafts with winds generally in the 30 to 40 mph range, well below severe limits, as storm heights remain relatively low with much of the instability in the low levels and skinny CAPE profiles in the mid to upper levels. Flash flooding remain somewhat of a threat, although flow aloft has remained strong enough to prevent issues to this point and unlike yesterday, we lack significant low level convergence to lead to training.

Pattern changes a bit tomorrow with an upper trough strengthening over the eastern US which will weaken the ridge offshore, leading to lower moisture with more westerly flow over the area. While there will still be moderate destabilization each afternoon Wednesday and Thursday, coverage will likely be more isolated each day with seasonably hot and humid conditions. A front will approach the area this weekend leading to the potential for more widespread showers GEFS probabilities of sbCAPE greater than 500 J/kg, on the low side for late May. Cooler temperatures generally expected as well, although there remains significant spread in blended guidance owing to uncertainty in the location of the front.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

A mix of MVFR and VFR cigs this afternoon as convection moves through. Shower/storm chances diminish this evening, but another round of morning cig restrictions possible.

Scattered storms are moving through the area early this afternoon and are expected to continue into this evening. The main hazards with convection will be reduced visibility from heavy rainfall and possible gusty winds toward 25-35 kts. There have also been some lingering MVFR ceilings in spots, but these are expected to continue to raise through the afternoon. Winds through the afternoon should remain out of the south around 5-9 kts. Convection should gradually wane this evening before mostly dry conditions are expected tonight. As has been the trend, another round of ceilings restrictions will be possible tonight as bountiful low level moisture remains in place. There is less confidence across guidance in how low cigs get, but at least periods of MVFR ceilings seem possible after 06-08z. Will need to continue to evaluate if IFR cigs become more likely. Any restrictions should slowly lift through the morning with VFR conditions returning near the end of the TAF period with 5-8 kt winds out of the southwest.

EXTENDED AVIATION OUTLOOK...Morning fog/stratus possible each day this week. Scattered, diurnally driven convection expected through Friday.

CAE WATCHES/WARNINGS/ADVISORIES

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