textproduct: Columbia

WHAT HAS CHANGED

Aviation Discussion updated for 12z TAFs.

KEY MESSAGES

- 1. Above normal temperatures through the weekend will increase the risk of heat-related illness.

- 2. Thunderstorm chances are forecast to increase over the next couple of days, with unsettled weather potentially continuing into next week.

DISCUSSION

Key Message 1: Above normal temperatures through the weekend will increase the risk of heat-related illness.

We continue to see above normal temperatures across the area today and on Sunday as upper level ridging remains situated atop the southeastern CONUS. This is forecast to slowly begin breaking down over the next several days as troughing pushes eastward. However, ahead of this, a very warm airmass remains in place across the area. 850 hPa temps are forecast to be in the 90th percentile both today and Sunday ahead of an approaching cold front. The airmass atop the area is not particularly moisture rich, which is helping to prevent this from being a particularly stifling stretch of heat across the area. Still, this is relatively unusual for mid June. Heat index values are forecast to be 103F-106F across the area both today and on Sunday, with low-level dewpoints mixing preventing us from seeing widespread heat indices >108F (our Heat Advisory criteria). Because of this, and expected convection this afternoon and especially Sunday afternoon, opted to hold off on issuing a Heat Advisory. Still, the heat will remain dangerous and precautions are advised today and Sunday. if you have any outdoor activities planned, please plan them for the morning or evening when temperatures are a bit cooler.

Key Message 2: Thunderstorm chances are forecast to increase over the next couple of days, with unsettled weather potentially continuing into next week.

The forecast remains on track over the next several days, with maybe a slight decrease in rain chances during the middle of next week compared to previous forecasts. A weak boundary is expected to hang out across the area today, specifically helping to focus convection across the central and eastern portions of the forecast area. The combination of this and the sea breeze may yield scattered storms in the coastal plain this evening within a pretty favorable environment for strong storms. It would not be surprising to see a severe storm with >1000 j/kg of MLCAPE, inverted V soundings, DCAPE of 1000-1200 j/kg, and TEI of 24-28. Storms are not expected to be widespread but given that environment, the storms that do develop may be strong. A more focused front looks to move into the area on Sunday, potentially providing an impetus for more convection. Guidance is mixed on overall coverage as a shortwave may move through at an unfavorable time of day, yielding some subsidence. This front should hang up or move through the area in the Monday-Wednesday timeframe, providing relief from the hot temps. However, it is unclear at this point how far south the front will actually sink. Tend to think the front will end up closer to the forecast area, helping to keep rain chances a bit more elevated than normal. This is especially the case with more west-southwesterly flow setting up atop the area as a trough axis digs into the south-central US. Additionally, persistently high IVT (90th percentile per NAEFS) should aid in keeping things unsettled early and mid week. By the end end of this upcoming week, it appears that another front may make it into the area & another focus for showers and storms.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

VFR conditions generally expected through the 24 hr forecast period.

Satellite indicating continued cirrus clouds over the area and there has been some intermittent MVFR vsbys in ground fog. Will make a last minute decision to include any tempos for brief fog 12z-13z. A weak boundary is expected to shift south through the area today with light and variable winds picking up to around 5 to 7 knots from the north to northwest after 14z and then shift more to the west by 18z through the early evening. Strong ridging should allow for another hot day with diurnal cumulus expected to develop with isolated convection mainly focused in the Coastal Plain and eastern Midlands after 20z so included a PROB30 at OGB. Otherwise winds should subside with sunset with another round of debris clouds in the evening.

EXTENDED AVIATION OUTLOOK...Isolated to widely scattered diurnal showers and storms possible later again on Sunday. Greater rain chances are expected early next week along with possible associated restrictions.

CAE WATCHES/WARNINGS/ADVISORIES

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