986 FXUS62 KCHS 291812 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 212 PM EDT Mon Jun 29 2026 .WHAT HAS CHANGED... All sections updated. && .KEY MESSAGES... - 1) A Heat Advisory is in effect for coastal southern SC and counties roughly south of I-16 in southeast GA as hot and humid conditions dominate the forecast area again today. - 2) High temperatures will be slightly above normal on Tuesday, then gradually rising through the holiday weekend. Heat Advisories could be needed during the holiday weekend across portions of our area. && .DISCUSSION... KEY MESSAGE 1: A Heat Advisory is in effect for coastal southern SC and counties roughly south of I-16 in southeast GA as hot and humid conditions dominate the forecast area again today. Today the region will remain under the eastern periphery of mid- level ridging centered over the Deep South. At the surface a weak boundary will attempt to slide southward across the forecast area as high pressure centered over New England nudges southward. While the upper level pattern remains a very similar synoptic setup to yesterday, the surface pattern is quite different. Whereas yesterday the flow at the surface was westerly, yielding a pinned sea breeze, today the flow will be much weaker and out of the NW. The sea breeze is expected to begin its inland progression around 2 PM, a few hours earlier than yesterday. With the surface setup today the region will see less mixing out of dew points, allowing heat index values to climb upwards of 108 degrees at several locations across the region. A Heat Advisory is in effect from Beaufort County, SC southward to counties roughly along and south of I-16 in southeastern GA through 6 PM this evening. Elsewhere conditions will still be hot and muggy, but in the 100-105 degree heat index range (shy of Heat Advisory criteria). A fly in the ointment in regards to today's forecast is the potential for afternoon convection. The 12Z CAMs are in fairly decent agreement on scattered to widespread coverage across southeastern GA, generally where the Heat Advisory is in effect. The Heat Advisory may be canceled early if the coverage of convection is great enough to lower heat index values below criteria. While widespread severe weather is not anticipated, forecast soundings show DCAPE values upwards of 1200 J/kg. Therefore, a strong to marginally severe storm is possible, especially where boundary interactions occur. KEY MESSAGE 2: High temperatures will be slightly above normal on Tuesday, then gradually rising through the holiday weekend. Heat Advisories could be needed during the holiday weekend across portions of our area. Ridging aloft will remain the dominant synoptic feature this week, initially centered over the TN Valley on Tuesday. It will then shift eastward towards the East Coast by the end of the week and remain in place through the holiday weekend. The main forecast highlight will continue to be the temperatures. Wednesday will feature highs slightly above normal, with temperatures warming to above normal into the holiday weekend. High temperatures could again reach into the mid to upper 90s late week and into the holiday weekend, which combined with dewpoint values in the 70s will likely yield heat index values in the 100-110 range. Heat Advisories could be required for portions of the forecast area at the end of the week and into the holiday weekend. Generally a dry forecast has been maintained, with PoPs trending upwards towards a more typical summertime pattern in the later half of the holiday weekend. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... Prevailing VFR through the 18Z TAF period at KCHS/KJZI/KSAV. Winds at KCHS/KJZI initially out of the NW around 18Z will shift to the S/SE as the afternoon sea breeze works its way inland over the next hour or so. KSAV has the best chance of seeing afternoon showers/thunderstorms today, with a TEMPO group in place from 18 to 21Z. Once convection wanes this evening conditions overnight should remain precipitation free, with winds shifting back to the NE in the early morning hours. Extended Aviation Outlook: Brief flight restrictions are possible with isolated showers and thunderstorms Tuesday afternoon. && .MARINE... Rest of This Afternoon and Tonight: SE winds this afternoon gusting to around 10 to 15 knots will shift to the NE, remaining elevated. Extended Marine: The synoptic pattern will generally support winds from the NE or E through Thursday. Then, they will clock around to the SW by Friday morning. Friday into the holiday weekend, winds will have a typical summertime pattern. This will consist of some backing during the day, with the highest winds along the land/sea interface with the formation of the sea breeze. Gusts could approach 20 kt, especially in Charleston Harbor as the sea breeze moves through. At night, expect winds to veer and possibly ease a few kt. Seas should stay 5 ft or less. No Small Craft Advisories are expected. && .CLIMATE... Record High Temperatures: June 29: KCHS: 99/1998 KSAV: 101/1959 July 4: KCHS: 98/2023 KSAV: 99/1997 Record High Minimum Temperatures: July 3: KCHS: 78/2016 July 4: KCHS: 79/2016 KSAV: 79/1931 && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Heat Advisory until 6 PM EDT this evening for GAZ114-115-137- 216>219-238>241. SC...Heat Advisory until 6 PM EDT this evening for SCZ148-151. MARINE...None. && $$