textproduct: Charleston

WHAT HAS CHANGED

The Aviation Section was updated to reflect the 12Z TAFs.

KEY MESSAGES

- 1) Hot and humid conditions are expected across the area this weekend and through early next week. Heat Advisories could be needed.

DISCUSSION

KEY MESSAGE 1: Hot and humid conditions are expected across the area this weekend and through early next week. Heat Advisories could be needed.

We continue to be sandwiched between a rather deep upper trough over the Great Lakes region and ridging out over the open Atlantic keeping us rather toasty across the area through the weekend. To add a bigger fly to the proverbial ointment, a rather broad but weak mid level area of low pressure sitting over the eastern Gulf has certainly made things a little tricky. Given its placement within the large scale pattern it is likely assisting in keeping the ridge in place at least for a day or two longer. Couple this with possibly some extra latent heat being released and ventilated to the northeast of this low (think of a car engine releasing heat, big clusters of storms do the same) and its easy to see why we overachieved some yesterday on our temperatures and heat indices. We saw some areas reach heat indices of 110 to 112 this afternoon as temperatures aided by the stout ridge climbed into the upper 90s including here at CHS. Little change is expected in the pattern and thus forecast for today as the ridge is still firmly in control over the area. The aforementioned low is expected to slowly drift just a bit west into the Gulf leading to even better quality moisture to surge northward into the Carolinas. PWATS are expected to climb to around 2 to 2.1 inches today. This increased moisture should allow for dewpoints to continue to flirt in the mid to upper 70s inland to low 80s along and behind the seabreeze. Those dewpoints coupled with baking in the sun setup the perfect recipe for more widespread heat indices in the 105 to 110 range and even a few spots approaching 112 along the immediate coast. Given we overachieved yesterday, the current forecast reflects some adjustments to account for that within the guidance and a heat advisory has been issued for the entire area. The only area that may not reach the 108 criteria is interior parts of Georgia where afternoon storms along the seabreeze could occur early enough to thwart reaching the official criteria. However, current hi-res guidance does support yet another late fire (3 to 4 pm) for seabreeze storms which could be enough time to reach 108. Nonetheless, whether its 105 or 108 its going to feel awful out once again.

Looking towards early next week, the upper ridge should finally begin to breakdown as our wandering low in the Gulf slowly meanders west towards Louisiana. This should help kick the rest of the pattern east a bit to increase storm coverage by Monday. While heat indices will likely continue to hover in and around 105 to 108, we may start to see enough coverage in storms each afternoon to keep things mostly in check. Any further advisories will likely be tied to how each days convection evolves and what areas are expected to remain rain free.

AVIATION /12Z SATURDAY THROUGH WEDNESDAY/

12Z TAFs: VFR conditions will prevail through the period. Hi- res guidance continues to indicate that seabreeze should develop and progress inland between 18-19Z. As this boundary pushes inland, the winds should veer out of the south with gusts up to around 20 knots at KCHS/KJZI as this boundary passes through. Isolated to scattered showers and thunderstorms could develop late this afternoon around 20 to 22Z. The best chance for a storm looks to be across eastern Georgia potentially around the SAV terminal prior to sunset.

Extended Aviation Outlook: Predominately VFR conditions through the period, however there is a low chance of brief flight restrictions each afternoon from showers and thunderstorms developing along the seabreeze.

MARINE

Today: As the local waters situate itself between an inland trough and a subtropical high to the east, this will allow for the pressure gradient to strengthen throughout the day. Expect wind speeds to range from 15 to 20 kts with gusts up to 25 kts (esp. across the South Carolina waters). Thus, a Small Craft Advisory (SCA) has been issued for the nearshore South Carolina waters (not including the Charleston Harbor) this evening (8PM) through early Sunday morning. Expect seas to range from 2 to 3 ft, before increasing 3 to 5 ft in the nearshore waters and 4 to 6 ft in the offshore waters (highest across the 20-60nm out from South Santee, SC to Savannah, GA).

Sunday through Wednesday: As the aforementioned inland trough shifts offshore early next week, there's another chance that we'll need SCAs on Sunday (esp. across the nearshore Charleston waters + Charleston Harbor). There is a low chance (30%) for a low pressure system to develop across the northeastern Gulf this weekend. If this system were to track up the Southeast coastline, then we'll likely need additional wind and wave concerns.

CLIMATE

Record High Minimum Temperatures:

July 17: KCHS: 79/2025

July 18: KCHS: 79/2007 KCXM: 81/2007

July 19: KCHS: 79/1986 KCXM: 83/1986

July 20: KCHS: 79/2025 KCXM: 83/2000 KSAV: 79/1942

July 21: KCHS: 80/1986 KCXM: 83/1998

July 22: KCHS: 81/2011 KCXM: 83/2011

CHS WATCHES/WARNINGS/ADVISORIES

GA...Heat Advisory from noon today to 8 PM EDT this evening for GAZ087-088-099>101-114-115-137-216>219-238>241. SC...Heat Advisory from noon today to 8 PM EDT this evening for SCZ040-042>045-147>152. MARINE...Small Craft Advisory from 8 PM this evening to 6 AM EDT Sunday for AMZ360-362.