textproduct: Columbia

WHAT HAS CHANGED

Aviation discussion updated for 00z TAFs.

KEY MESSAGES

- 1. Diurnal showers and thunderstorms, some strong, each day.

- 2. Increasing heat and humidity is expected next week.

DISCUSSION

- 1. Diurnal showers and thunderstorms, some strong, each day.

More of the same pattern is expected through the weekend and well into next week. Onshore surface flow, in conjunction with a strong Bermuda high over the western Atlantic will continue to provide significant low-level moisture to the region. Shower and thunderstorm coverage should begin to decrease this weekend, with the focus shifting closer to the coast as the ridge begins to flatten. However, dewpoints are expected to remain in the low to mid 70s over the next several days. Daily SBCAPE values should also remain more than sufficient to support diurnal chances for showers and thunderstorms, so the potential for additional convection will remain despite the overall decrease in coverage. Strong storms are capable each day, as sufficient CAPE will support the potential for wet microbursts within the strongest convection.

- 2. Increasing heat and humidity is expected next week.

A low amplitude upper level ridge is forecast to begin developing over the next several days, with 90th percentile 500 hPa heights overspreading the area by Sunday. With southwesterly flow common and afternoon storm coverage expected to lower a bit by early next week, afternoon highs are forecast to bump up into the mid 90s. With persistently high dewpoints in the low to mid 70s, LREF guidance continues to indicate a high likelihood of daily, peak heat index value exceeding 100F. While this isn't at heat advisory criteria, it isn't crazy to think we may have a day or two next week where we approach 105F-108F for afternoon heat index values. This should become more likely by Thursday, Friday and Saturday of next week as 95th-99th percentile heights are shown by the LREF guidance. An EFI signal for heat exists in this timeframe and individual global model show a more sustained lull in precip chances. As a result, the most intense heat of the period is likely to arrive by the end of this upcoming week.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

VFR conditions likely through Sunday morning, then possible stratus/fog again during the predawn hours.

Little change in the environment overall with plenty of low level moisture in place with general upper level ridging aloft. Some convection along surface trough northwest of the area should remain north of the terminals this evening. Southeasterly winds should subside to around 3 knots or less overnight before picking up again after 15z Sunday from the south. Guidance is mixed with stratus/fog formation but given little change in environment will continue more of a persistence forecast and have a period of restrictions in a tempo group. Isolated convection expected again Sunday afternoon but coverage not expected to be enough to include in this forecast.

EXTENDED AVIATION OUTLOOK...A seasonal pattern of early morning restrictions and diurnal thunderstorms is likely through much of the extended.

CAE WATCHES/WARNINGS/ADVISORIES

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