textproduct: Columbia

WHAT HAS CHANGED

Key messages remain the same for this forecast package. Aviation discussion updated for 06z 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.

Upper-level ridging is expected to strengthen by next week, which should help keep shower and thunderstorm coverage generally isolated, though daily storm chances will remain possible. There is also a signal, albeit an inconsistent once, that a deeper trough could move into the eastern CONUS towards the end of next week, potentially increasing storm coverage once again.

- 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 /06Z SATURDAY THROUGH WEDNESDAY/

IFR restrictions possible this morning.

Light surface winds and dry air aloft should yield another round of restrictions this morning. HREF guidance shows stratus pushing in from the coast overnight with SE flow in place. Lamp guidance is starting to show more of a signal for stratus developing mainly after 09z. However, prone areas like AGS/OGB may see restrictions starting earlier. Reduced visibilities will also be possible, although with no TAF sites receiving heavy rain today, any fog may not be as dense as the past few mornings. Restrictions should ease by 13Z or 14Z with light SE winds of 5 to 10 kts into this afternoon. Shower and thunderstorm coverage today seems to be less than the past few days, with the best chance at OGB. Have handled the potential for -TSRA with a PROB30 there, and only VCSH at the other terminals where confidence is lower.

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.