textproduct: Columbia

WHAT HAS CHANGED

Little change in the overall forecast, with daily afternoon storm chances and increasing heat/humidity next week. Aviation discussion updated for 18z 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.

Onshore surface flow in conjunction with the strong bermuda high across the western Atlantic is forecast to continue providing significant surface moisture to the region. Dewpoints are forecast to remain in the low to mid 70s over the next several days and into next week, with daily SBCAPE values more than sufficient to yield diurnal chances for showers and thunderstorms. We're seeing a nice inverted surface trough push through the coastal plain this afternoon, forcing scattered showers and thunderstorms. A similar picture is likely to be painted over the next few days as we continue to reside on the southwestern side of this expansive surface high. Upper level ridging is forecast to build in by next week, likely helping to keep showers/storms more isolated to scattered in nature, but the daily chances will remain. There is a signal, albeit inconsistent, that a deeper trough will push into the eastern CONUS by the end of next week, helping to possibly increase storm coverage again. Strong storms will be a possibility each day as CAPE will be sufficient for wet microbursts in 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. Be sure to practice good habits when dealing with the heat next week!

AVIATION /16Z FRIDAY THROUGH TUESDAY/

Mix of VFR with scattered storms and associated restrictions this afternoon.

Typical summer afternoon unfolding with scattered thunderstorms across the region. Coverage is modest so only included a mix of vicinity TS and prob30s, outside of OGB, for the time being; storm chances are lower at AGS and DNL, but possible this evening. Restrictions are expected within any showers- storms with gusty variable winds and reduced vsby. These will continue through the afternoon and evening for all TAF sites. Overnight and into Saturday, additional cig restrictions are likely with IFR or LIFR stratus in the morning.

EXTENDED AVIATION OUTLOOK...Diurnal thunderstorm restrictions possible through the period, with additional early morning restrictions also possible each day.

CAE WATCHES/WARNINGS/ADVISORIES

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