textproduct: Charleston

WHAT HAS CHANGED

The aviation section has been updated for the 06Z TAF issuance.

KEY MESSAGES

- 1) A period of unsettled and warm conditions starts today and continues into the weekend.

DISCUSSION

KEY MESSAGE 1: A period of unsettled and warm conditions starts today and continues into the weekend.

A ridge of high pressure will remain over the Gulf/Caribbean into the weekend, with a slow moving surface high pressure pushing eastwards into the Atlantic. This will result in a warm and moist southwesterly boundary layer, with temperatures throughout the atmospheric column consistently reaching and/or exceeding the 90th percentile wrt climatology, as the latest ensemble situational awareness tables continue to show, making it feel more like April than February over the next couple days. Highs today are expected to reach up into the mid 70s to lower 80s for inland areas, closer to the upper 60s to lower 70s along the coast, with dewpoint temperatures largely in the 60s. The warm highs expand into Friday, with widespread lower 80s for inland areas, lowering a touch into Saturday in the upper 70s to lower 80s. The latest forecast continues to keep any records at bay, though we'll get closest to the records set for February 20 as we'll be warmest that day with inland areas in the lower to mid 80s.

In addition to creating warm temperatures, positive theta-e advection will result in weak synoptic lift at times over the next couple days as well. Amidst precipitable water values near 1.25", the weak lift will create periods of scattered showers, though without a strong forcing mechanism rainfall amounts will remain on the light side at under a tenth of an inch. While confidence is high that scattered showers will form in this environment today and Friday, confidence in the spatial extent and timing of the showers is on the lower side given the lack of strong forcing mechanism.

On Saturday, guidance continues to indicate that a cold front will be approaching the area from the north. In addition to the light scattered showers, isolated thunderstorms may develop as instability builds out ahead of the front, especially Saturday afternoon. While details remain unclear, some of the models are suggesting 500+ J/kg of SBCAPE and 40+ knots of deep layer shear may be available, with various AI/ML output suggesting the need for monitoring for strong to severe thunderstorms Saturday afternoon.

Scattered showers and isolated thunderstorms move off into the near- shore Atlantic waters overnight into Sunday, with the cold front moving through bringing an end to the warm and unsettled conditions.

AVIATION /06Z THURSDAY THROUGH MONDAY/

VFR conditions are expected at CHS/JZI/SAV terminals through 06Z Friday. Rounds of mid and high clouds should continue to pass over the terminals through the TAF period. Southwest winds should strengthen with gusts between 15 to 20 kts once mixing begins around 15Z. Each TAF will feature a PROB30 for light showers from 19-22Z. Gusts should end around sunset.

Extended Aviation Outlook: The potential for flight restrictions will increase late week into the weekend with possible fog development during the pre-dawn hours, as well as increasing rain chances especially Friday and Saturday.

MARINE

The marine zones will remain between high pressure centered over the western Atlantic and low pressure over the Mid-West. This pattern will support southwest winds generally around 15 kts with 3 to 5 ft seas today through tonight. The pressure gradient pinches on Friday, wind gusts across a portion of the SC waters may gusts to around 25 kts during the daylight hours. Small Craft Advisories could be needed, especially for the Charleston County nearshore waters. A frontal wave is forecast to develop over the I-20 corridor of the Deep South Friday night, tracking east on Saturday. The associated cold front is timed to push over the marine zones Saturday evening, with CAA and strengthening winds Saturday night. On Sunday, Small Craft Advisory conditions should spread across the nearshore SC/GA waters with gales possible across the outer GA waters. Gusty winds and elevated seas may linger into Monday.

Sea Fog: The pressure pattern will support southwest winds, generally parallel to the coast through the rest of the week. The southwest winds should provide dewpoints in the upper 50s to low 60s this afternoon through Saturday. Buoy observations indicate that the nearshore water temperatures generally range in the low 50s. Given parallel winds and dewpoints nearly 10 degrees warmer than the water temperatures, at least patchy sea fog is expected. Probabilistic guidance shows likely values of visibility less than 0.5 miles at times late this week. The sea fog potential will be limited by gusty conditions and rounds of showers.

CLIMATE

Record High Temperatures:

February 20: KCHS: 82/2018 KCXM: 78/1918 KSAV: 84/1991

CHS WATCHES/WARNINGS/ADVISORIES

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