textproduct: Charleston

WHAT HAS CHANGED

All sections updated.

KEY MESSAGES

- 1) Locally heavy rainfall possible again Monday. Thereafter, rain chances will steadily diminish through the rest of the week.

-2) Hot and humid conditions will return Wednesday and persist into the weekend.

DISCUSSION

KEY MESSAGE 1: Locally heavy rainfall possible again Monday. Thereafter, rain chances will steadily diminish through the rest of the week.

Overnight into Monday: The pattern will remain the same overnight featuring a very moist airmass with precipitable water values around 2.25 inches. Onshore flow will persist as well, and the setup will favor showers and thunderstorms loading up offshore and then making a run for the coast and attempting to push inland. Late tonight, model guidance is once again favoring the southeast GA coast for being in the trajectory of showers and storms tracking toward the coast. Timing remains a bit of a question, but chances should increase along the coast around and just after sunrise. This shower and thunderstorm activity should gradually push inland through the morning. Focus for the afternoon will be along differential heating boundaries starting in the early afternoon along the southeast SC coast. Any early afternoon activity should then gradually push inland into the evening. Locally heavy rainfall will be the main concern throughout the day. With such high precipitable water values, any showers and storms that develop will be efficient rainfall producers. However, there should be just enough forward motion to keep the overall flash flood threat down. Still, there could be some isolated locations that see pockets of 2+ inches.

Rest of this Week: The troughing in the mid levels will begin to break down tomorrow while mid level ridging builds into the area through the remainder of the week. As the ridging slowly builds precipitation chances will slowly dwindle each day, with PoPs only around 15% by Friday afternoon.

KEY MESSAGE 2: Hot and humid conditions will return Wednesday and persist into the weekend.

Its appearing like summer heat will try to make a final stand by the end of the week as high pressure over the central US flattens out and slowly extends across the Mid- Atlantic. We look to be on the southern Periphery of this ridge and with ample subsidence a loft, drier conditions are expected to return across the area mid to late week. Unfortunately with the drier conditions comes hotter temperatures as highs will likely climb back into the mid to upper 90s. with all the sunshine. Looking at some of the ensemble guidance and the ECMWF extreme forecast index (EFI), this heat does not look to pack the same punch as our heat wave earlier in the summer given our position with respect to the ridge. Overall conditions are leaning a little above normal climatology which is expected from a stout ridge; however, there remains a decent amount of uncertainty within the guidance on the strength of the ride especially Thursday through Saturday. IF the ridge ends up trending a little stronger then we could certainly see things trend a little warmer than we currently have it and the potential for heat products would also increase. Nonetheless, it does appear likely for our heat indices to climb back into the 105 to 110 range with the hottest days likely Friday and Saturday and would not be shocked if a heat advisory or two may be needed late week but plenty of time to monitor.

AVIATION /00Z MONDAY THROUGH FRIDAY/

The 00z TAF period begins with VFR conditions at KCHS, KJZI, and KSAV. The first concern is the potential for low stratus to develop late tonight. Model guidance suggests that the best chances of IFR ceilings will be just inland of the TAF sites, but all 3 will be at risk. For now we have kept the forecast MVFR, but do include these ceilings at all 3 sites starting around 10z. This stratus, if it develops, could stick around through mid to late morning. The next concern is for showers and thunderstorms to move onshore. Guidance is again favoring the southeast GA coast, meaning the best chances appear to be at KSAV beginning around 12z. This activity will likely continue through midday. At KCHS and KJZI, the best chances will likely come in the early afternoon hours.

Extended Aviation Outlook: Periodic flight restrictions are expected in showers and thunderstorms through the first half of the week before more IFR conditions prevail late week.

MARINE

Through Tonight: E/NE winds will redevelop again tonight. Speeds look to remain less than 15 kt (outside of convection) with seas 2-3 ft. Another round of convection could develop across the GA waters early Monday morning.

Monday night through Saturday: No marine concerns expected. Light and variable prevailing flow will shift onshore each afternoon as the sea breeze circulation develops along the coast, with 2-3 ft seas.

CHS WATCHES/WARNINGS/ADVISORIES

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