textproduct: Charleston

WHAT HAS CHANGED

All sections have been updated.

KEY MESSAGES

- 1) Warm temperatures will continue, with isolated to scattered showers and thunderstorms possible through Saturday.

- 2) A cold front will bring increased rain chances Sunday afternoon into Monday morning, followed by cooler temperatures.

DISCUSSION

KEY MESSAGE 1: Warm temperatures will continue, with isolated to scattered showers and thunderstorms possible through Saturday.

Through this evening: Diurnal showers, and an embedded thunderstorm or two, will continue to gradually progress inland. The best axis of convergence and instability is currently aligned just inland of I-95 across southeast GA extending up into Hampton and Allendale counties. This activity is being fueled by a narrow corridor of MLCAPE values up to around 1,000 J/kg. While updraft strength has been pretty meager, there is enough moisture and slow storm motion to produce some pockets of decent rainfall. Gage amounts are mostly in the 0.25-0.50" range, but MRMS data suggests there are some isolated locations of more than an inch. In fact, a very localized heavy rainfall event has been ongoing along the Effingham/Chatham County line. Several home weather stations have recorded 3-4 inches of rain, meanwhile just 5 miles away KSAV has already measured 0.01: so far. The severe threat remains virtually zero and this axis of showers and storms will push inland through the late afternoon and more into central GA/SC by the early evening.

Saturday is expected to bring another warm day with highs rising into the low to mid 80s away from the immediate coast. Without the benefit of the subtle coastal trough moving onshore like today, Saturday is expected to bring far less coverage of showers and storms. Instead, the bulk of the activity is expected to be much further inland. The best chance for isolated to scattered diurnal convection will be across the interior counties including Tattnall, Candler, Evans, Bulloch, Jenkins, Screven, and Allendale. Much like today, no severe threat is expected.

KEY MESSAGE 2: A cold front will bring increased rain chances Sunday afternoon into Monday morning, followed by cooler temperatures.

The mid-levels will consist of a broad trough over the eastern half of the U.S. Sunday and Monday. At the surface, a cold front will be approaching our region from the west and northwest on Sunday. The front will usher a plume of deep moisture from the Gulf into our region. PWATs should peak ~1.7" which is above the 90% mark for CHS sounding climatology, per SPC. The combination of lift and moisture should generate some rain across our area from Sunday afternoon into Monday morning. While there remain some differences in QPF amounts between the models, the general consensus is storm total below 0.3". So this won't be enough rain to put much of a dent in the drought or cause flooding issues. Otherwise, POPs generally peak in the chance to likely category. As far as the thunderstorms potential, there is minimal instability in place ahead of the front. So there could be a few rumbles of thunder ahead of and with the front, but the severe risk is very low. The front will move through Sunday night, followed by drier conditions by later Monday. As for high temperatures, ahead of the front they'll remain well above normal, generally in the 80s, except cooler at/near the beaches. Behind the front, temperatures drop to near seasonal levels on Monday, then generally continuing through the middle of next week. Temperatures rise towards the end of next week.

AVIATION /18Z FRIDAY THROUGH WEDNESDAY/

Overall, VFR conditions are expected to prevail at KCHS, KJZI, and KSAV through 18z Saturday. For the first hour or two of the TAF period, we could still see MVFR ceilings at KCHS and KSAV as well as a brief shower at KSAV. All of this activity should continue to push inland through the late afternoon hours. Overnight, there is potential for fog and stratus but current guidance favors it inland of the TAF sites. Perhaps KSAV has the best chance of seeing a period of fog or stratus right around sunrise, but confidence is too low to include in any of the TAF's. Towards the end of the 18z TAF period, there could again be isolated to scattered showers and thunderstorms. However, this activity should set up much further inland than it has so far today.

Extended Aviation Outlook: A cold front will bring higher probabilities for flight restrictions Sunday afternoon through Monday morning, followed by gusty northerly winds on Monday.

MARINE

Through Saturday night: Overall, conditions should remain pretty quiet and below Small Craft Advisory thresholds. Winds will continue to be primarily onshore with speeds mostly topping out in the 10-15 knot range. Seas are expected to be 2-4 feet across the nearshore waters and 3-5 feet across the outer waters.

Next Week: A cold front will then approach from the west and northwest on Sunday, moving through the waters Sunday night. Expect a surge in winds and seas behind the front. Small Craft Advisories should be needed across most of our coastal waters Monday, and could persist across portions of our waters into the middle of next week.

CHS WATCHES/WARNINGS/ADVISORIES

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