textproduct: Columbia

WHAT HAS CHANGED

Updated key messages for declining storm chances tonight. Aviation discussion updated for 00z TAFs.

KEY MESSAGES

- 1. Scattered storms expected Saturday afternoons with widespread showers and storms Sunday and Monday associated with a front.

- 2. Hot, humid and breezy conditions continue with cooler conditions associated with the front late weekend into next week.

DISCUSSION

Key Message 1: Scattered storms expected Saturday afternoons with widespread showers and storms Sunday and Monday associated with a front.

Essentially all of the thunderstorm activity from this afternoon and early evening has moved out of the forecast area. With how worked over the atmosphere is behind this activity, any additional shower or storm chances tonight will be limited. So, PoPs have been lowered to just slight chance at best.

Tomorrow scattered storms expected once again with coverage similar or slightly higher with a bit stronger upper level support as the weak ridging that we remained somewhat under the influence shifts to the east and weak shortwaves move through a more zonal flow. In addition, PWATs expected to increase with SPC HREF mean showing values greater than 2 inches over most of the forecast area. Environment may be slightly weaker to support severe storms based on HiRes forecast soundings with weaker cloud layer shear and not quite as unstable an environment but we remain in a marginal risk for tomorrow with the potential for a few storms to produce strong to marginally severe wind gusts.

As a front approaches the area Sunday into Monday, blended guidance supports widespread showers and storms near the front each day, favoring the afternoons where moderate instability will develop. While widespread severe weather is not expected, especially Monday where instability may struggle to develop, a few storms could approach severe limits. Storms will likely have efficient rain rates, although flow will be sufficient enough to cause major flooding concerns. It will be worth monitoring potential training with the flow generally parallel to the front. Ensemble means favor drier air pushing into the area by the middle of next week.

Key Message 2: Hot, humid and breezy conditions continue with cooler conditions associated with the front late weekend into next week.

Hot, humid and breezy conditions continue with the hottest days of the period expected to be today and tomorrow. The increased convective coverage both today and tomorrow may limit the extent of our high temperature and heat index but continue to expect triple digit heat indices for today and tomorrow with highs in the mid to upper 90s and dew points remaining in the 70s. Blended guidance IQR continues to favor lower temperatures associated with the approaching front and widespread clouds and convection each day. Given the recent hot weather, the NBM takes that into account and will likely have a warm bias. So, I would not be surprised if we end up toward the cooler end of the IQR. This air mass will be very humid, with blended dew points continuing in the low to mid 70s.

AVIATION /00Z SATURDAY THROUGH WEDNESDAY/

VFR conditions likely through much of the TAF period, with some morning fog possible and afternoon convection.

Convective has pushed out of the forecast area, confined now to the coastal plain and north of CLT. Mid-level cloud cover and light west-southwest winds will continue overnight into Saturday morning. With rainfall at AGS, some morning fog is possible but too low confidence in restrictions to mention any in the TAF's yet. Otherwise, Saturday will be much of the same as Friday with strengthening west-southwest winds by late morning and typical summer cu. Afternoon showers-storms are likely again with enough confidence for a prob30 right now.

EXTENDED AVIATION OUTLOOK...Increasing chances for afternoon storms Sunday and into early next week.

CAE WATCHES/WARNINGS/ADVISORIES

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