textproduct: Charleston

WHAT HAS CHANGED

Aviation section updated for the 12Z TAFs.

KEY MESSAGES

- 1) Record high temperatures possible this afternoon.

- 2) Cooler temperatures Tuesday and Wednesday, followed by rising temperatures Thursday into the weekend. Increasing rain chances late this week.

- 3) Minor coastal flooding possible with the Tuesday midday high tide along the Charleston and Colleton county coasts.

DISCUSSION

KEY MESSAGE 1: Record high temperatures possible this afternoon.

Near term guidance indicates that the center of a 594 dm ridge will settle over northern AL this afternoon, ridging east over the forecast area. This pattern will support very mild llvl thicknesses across SE GA/SC. At the sfc, the center of a large 1025 mb high will shift over the Great Lakes this afternoon, with a weak inverted trough over the forecast area. This pattern should support light NW winds this morning, aiding in pinning the sea breeze until the mid to late afternoon. Given the very warm llvl thicknesses, strong insolation, and later sea breeze should favor high temperatures in the mid to upper 90s. Record high temperatures a KCHS and KSAV could be tied or broken, see Climate section below.

KEY MESSAGE 2: Cooler temperatures Tuesday and Wednesday, followed by rising temperatures Thursday into the weekend. Increasing rain chances late this week.

A cold front will be located south of our waters early Tuesday morning, and quickly moving away. As it shifts south, the deterministic models and CAMs indicate the potential for convection, but disagree on the coverage. Given the synoptic setup, the anticipation is a band of scattered showers and isolated thunderstorms could form late in the morning, especially south of I- 16. This activity will shift south and out of our area during the afternoon as drier air builds in from the north. Then, the High will persist to our north through midweek, bringing our area dry conditions.

But the most noteworthy thing from this front will be the temperatures. Northeast winds behind the front will usher "cooler" temperatures into our area. They will be near normal on Tuesday and Wednesday, with Wednesday being the "cooler" of the two days. As the High starts to shift offshore on Thursday and into Friday, high temperatures will trend upwards. This upward trend will continue into the weekend. Rain chances will also increase Friday into the weekend.

KEY MESSAGE 3: Minor coastal flooding possible with the Tuesday midday high tide along the Charleston and Colleton county coasts.

Minor coastal flooding is possible with the Tuesday midday high tide along the Charleston and Colleton County coasts. Strengthening northeast winds are expected on Tuesday, which will increase tidal departures. The tide would need ~1 ft departure to reach minor flooding thresholds of 7 ft MLLW in the Charleston Harbor. Most guidance indicates this could be achieved, with tide levels possibly rising to the 7.0-7.2 ft MLLW range. A Coastal Flood Advisory could be needed. No issues are expected further south along the lower SC and southeast GA coasts.

AVIATION /12Z MONDAY THROUGH FRIDAY/

12Z TAFs: VFR with light to calm winds early, then turning from the NW by 14z. A weak sea breeze is forecast to push inland this afternoon, turning winds from the SSE.

Extended Aviation Outlook: VFR. Gusty winds are possible Tuesday through Thursday afternoons.

MARINE

Today: The pressure pattern will generally support southeast winds between 5 to 10 kts across the marine zones. Wave heights are forecast to remain between 2 to 3 ft.

Tonight: A backdoor cold front should advance across the marine zones tonight. High pressure will surge across the Atlantic waters tonight, resulting in gusty NE winds to develop after 6Z. Gusts across the SC waters are forecast to remain just below 25 kts during the overnight hours. Waves should steadily build through the night, reaching 3 to 5 ft across the nearshore and outer SC waters before 12Z.

Extended Marine: A cold front will be located south of our waters early Tuesday morning, and quickly moving away. Meanwhile, High pressure will be building in from the north, and it's expected to persist there through midweek. This will cause NE winds to quickly increase to a strong breeze on Tuesday. Gusts could even reach near gale across portions of our waters, especially across our GA waters. Winds should ease some Tuesday evening and night, followed by increasing again to about the same strength on Wednesday. The same wind decrease occurs again Wednesday night. The High shifts offshore on Thursday, limiting the increase in winds during the day. Winds should ease more Thursday night into Friday. Likewise, wind-driven seas will be elevated Tuesday through Thursday. Small Craft Advisories will be needed for all of our waters Tuesday morning. These Advisories could remain in effect for some of our marine zones through Thursday.

Rip Currents: The combination of gusty northeast winds and elevated seas Tuesday into midweek will lead to an elevated risk of rip currents. On Tuesday there is a Moderate Risk for our SC beaches and a High Risk for our GA beaches.

CLIMATE

Record High Temperatures:

September 14: KCHS: 94/1991 KCXM: 94/1938 KSAV: 96/1991

Record High Minimum Temperatures:

September 14: KSAV: 77/1979

September 20: KCHS: 76/1954

CHS WATCHES/WARNINGS/ADVISORIES

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