textproduct: Columbia

WHAT HAS CHANGED

Lowered temperatures a bit for tomorrow afternoon. Aviation Discussion updated for 18z TAFs.

KEY MESSAGES

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

- 2. Isolated thunderstorms today; rain chances increase over the weekend into early next week.

DISCUSSION

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

Conditions are expected to continue to be quite hot through the weekend with the axis of the ridge overhead peaking, bringing the hottest temperatures so far this year. 90th+ percentile upper ridging and moist low level south-southwest flow over the state will persist into the weekend. High temperatures will continue to be in the mid to upper 90s today through Sunday with dewpoints in the mid 60s to low 70s in the afternoon. This is expected to lead to Heat Index values peaking in the low 100s with some values in the 105-108F range possible. Given this will be some of the hottest temperatures and heat indices so far in 2026, there is currently a Heat Advisory in effect for the northern and eastern Midlands, where most of the hottest heat indices are occurring this afternoon. Although there is still low confidence we will exceed criteria (HI of 108F-112F), these early season heat waves tend to contribute to a higher risk for heat-related illness, so we are messaging extreme caution. Additionally, the experimental Heat Risk category of Major (3 out of 4) will be in place for the entire forecast area today, with even some Extreme (4 out of 4) areas starting to show up over the weekend particularly in Columbia and Augusta.

Saturday is still expected to be just as warm as today, with the potential for Heat Advisories once again. However, we have decided to hold off at this time since there is a higher chance for convection during peak heating hours which could limit the potential for exceeding extended or large coverage. Temperatures Sunday are forecast to be a few degrees lower ahead of an approaching frontal zone as the ridge attempts to hold across the Southeast. Conditions will be monitored but widespread Head Advisory criteria remain less likely at this time. A cooling trend is expected to develop into the new work week as the influence of the ridge weakens.

Key Message 2: Isolated thunderstorms today; rain chances increase over the weekend into early next week.

A classic summertime convective pattern is expected to remain in place across the region through the weekend, supporting daily chances for afternoon and evening convection. Surface high pressure will remain positioned east of the forecast area, while upper-level ridging will generally limit the overall coverage of showers and storms. Even with the ridging aloft, slightly above normal atmospheric moisture and strong daytime heating will allow conditions to destabilize. Expect isolated to scattered coverage each afternoon with some enhanced activity closer to the coast as interactions from the sea breeze move inland. Muggy conditions and intense heating today will allow for fairly strong instability, with over 2000 J/kg of sbCAPE. However, weak wind shear should prevent widespread organized convection. Instead, the environment will favor a few strong pulse-type thunderstorms capable of protecting localized damaging downburst winds. SPC has issued a Marginal Risk (1/5) for severe thunderstorms mainly north of a McCormick- Columbia- Sumter line, with a Slight risk (2/5) in the northernmost portion of Lancaster County including the Charlotte Metro today.

Similar conditions are expected Saturday ahead of an approaching frontal boundary. As the afternoon seabreeze interacts with 1500-2000 J/kg of CAPE, another round of more scattered showers and thunderstorms is possible, resembling activity observed the previous days. Similar activity is expected Sunday as a more pronounced shortwave tough moves into the region.

Moisture transport then increases early next week with NAEFS IVT percentiles over 90 percent of climatology, and remain elevated through at least the middle of next week. With this in mind, expect a more active pattern with above normal moisture (and subsequently lower temperatures given the higher rain chances) to kick in by Monday and last for several days.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

VFR conditions continue through this TAF period.

SCT cumulus are developing with 6-10 kt southwesterly to westerly winds across the area. The remainder of the afternoon should see these conditions continuing with isolated showers and storms possible, but like previous days, confidence in these impacting the terminals is low. Tonight, winds become light and variable as FEW to SCT cirrus pass through the region. After 14-16z Saturday, winds become a bit more westerly to northwesterly, but remain light as another cumulus deck develops. More afternoon showers/storms are possible just after this TAF period, where coverage may be slightly greater than has been seen recently.

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

CAE WATCHES/WARNINGS/ADVISORIES

SC...Heat Advisory until 8 PM EDT this evening for SCZ016-022-029- 031-038-115-116. GA...None.