textproduct: Charleston

WHAT HAS CHANGED

The Aviation section was updated for the 00z TAF issuance.

KEY MESSAGES

- 1) Rain to diminish tonight, but linger over parts of coastal Georgia.

- 2) Cooler temperatures along with breezy to windy conditions are expected into the middle of this week.

- 3) Coastal flooding and significant coastal hazards are expected during the middle of the week.

- 4) NHC has identified a system in the Gulf with a high chance of formation through seven days. Regardless of development, heavy rainfall could develop over the region by this weekend.

DISCUSSION

KEY MESSAGE 1: Rain to diminish through tonight, but linger over parts of coastal Georgia.

Moisture will likely remain sufficiently deep to support some degree of shower activity across the far southern areas through the night with the middle Georgia coast likely seeing the greatest coverage through daybreak Tuesday. It will become increasingly breezy along the coast late with wind gusts approaching 25-30 mph at the beaches as sunrise approaches. Winds on Lake Moultrie will also begin to respond. Lows tonight will range from the upper 50s/lower 60s inland to the upper 60s/near 70 at the beaches.

KEY MESSAGE 2: Cooler temperatures along with breezy to windy conditions are expected into the middle of this week.

The center of a 1025 mb high will settle over the Mid Atlantic states on Tuesday. Near-term guidance indicates that a sfc ridge will build southwest across the Carolinas into GA. To the south, a front will remain nearly stationary from the northern Gulf coast east across north Florida. The sfc pattern will support gusty northeast winds across the SC Lowcountry and SE GA on Tuesday. HREF indicates that dense cloud cover may remain along the coast, especially the GA coast, during the daylight hours. The combination of gusty NE winds, thick clouds, and isolate showers may favor the cooler guidance for high temperatures. Blending the NBM10 with NBM50, high temperatures are forecast to peak in the mid to upper 70s on Tuesday. Wind gusts across the coastal counties may exceed 35 mph at times, especially along the GA beaches.

Wednesday through Thursday, conditions across the forecast area will remain rain-free, supported by stable and dry east- northeast flow. However, winds will not be a strong as Tuesday, as the high center drifts over the western Atlantic and pressure gradient decreases. High temperatures should warm to around normals, ranging around 80 degrees.

KEY MESSAGE 3: Coastal flooding and significant coastal hazards are expected during the middle of the week.

Coastal Flooding: Strong northeast winds associated with a wedge of high pressure inland and low pressure offshore in combination with high astronomical tide levels will likely support coastal flooding issues this week. The pattern suggests a minor/moderate saltwater inundation setup Tuesday and Wednesday during late afternoon/early evening high tide cycles, with the greatest risk for moderate coastal flooding along Charleston and Coastal Colleton Counties. There is a more limited risk for minor coastal flooding issues into Thursday along the SC coast. Coastal Flood Advisories will likely be needed late this week.

Rip Currents/High Surf/Beach Erosion: The setup looks highly favorable for strong and dangerous longshore and rip currents Tuesday into Wednesday with gusty northeast winds expected. In addition, there will be an increased risk for high surf along the beaches with the latest guidance still showing a potential for 4-6 ft breakers developing in the surf zone (largest for coastal Georgia) by Tuesday afternoon and lingering into Wednesday. A High Surf Advisory should be needed for some beaches. Significant beach erosion is also likely, particularly around times of high tide. Guidance suggests beach erosion chances are highest around the Tuesday afternoon high tide.

KEY MESSAGE 4: NHC has identified a system in the Gulf with a high chance of formation through seven days. Regardless of development, heavy rainfall could develop over the region by this weekend.

An area of low pressure is expected to develop over the southwest Gulf over the next day or two. This system may organize and deepen as it tracks northeast across the Gulf later this week. Regardless of development, deep tropical moisture will likely build northward across the region, with PW values exceeding 2 inches. A wedge of high pressure should remain across the Carolinas and Georgia, likely supporting widespread isentropic lift. GFS and ECMWF and the AI variants indicates that some heavy rainfall may potentially develop along the coast, aided by a passing coastal low on Sunday.

AVIATION /00Z TUESDAY THROUGH SATURDAY/

The 00z TAF period begins with widespread stratus across the area, with MVFR/IFR ceilings impacting KCHS, KJZI, and KSAV. Overall, ceilings are expected to gradually lift over the next several hours and VFR conditions should return to the terminals by the early morning hours. KCHS and KJZI should then remain VFR through the rest of the period. At KSAV, MVFR ceilings should return Tuesday morning and could persist for much of the day. Showers will also be possible around the southeast GA coast from mid morning onward Tuesday. Northeast winds will increase Tuesday morning and gusts into the 20- 25 knot range can be expected throughout the day.

Extended Aviation Outlook: VFR. Breezy winds possible on Wednesday.

MARINE

Through Tonight: Northeast winds will steadily strengthen overnight as inland cold air damming become better established. Northeast winds will increase to 20-25 kt with gusts to 30 kt as daybreak approaches with seas building 3-5 ft.

Tuesday, the pressure gradient across the marine zones will tighten between a ridge of high pressure centered over the Carolinas and low pressure off the Atlantic coast of Florida. Northeast winds will strengthen quickly Tuesday morning, with gale wind gusts across the nearshore and offshore waters. Gale Warnings have been issued from 5 AM to 2 AM Wednesday. Seas will build quickly with the windy conditions, with 4-7 ft waves along the coast by the afternoon and 10-11 ft waves in all zones from 20-60nm offshore. Wind strength decreases into the overnight hours as the low pressure moves further out to sea, bringing an end to the Gale conditions during the early overnight hours on Wednesday. For the Charleston Harbor, the Small Craft Advisory expires at 2 AM.

Wednesday: The pinched surface pressure gradient continues into Wednesday, though wind gusts will have lowered into the 25 to 34 knot range which will necessitate the need for a Small Craft Advisory. Wave heights are expected to slowly subside on Wednesday, with 4 to 5 foot breaker waves along the coast by the evening hours. In the 20-60nm offshore zones expect 6 to 9 foot waves by the evening hours, highest in the Savannah to Altamaha Sound zone.

Thurday-Friday: Conditions are expected to improve on Thursday, though rough seas will likely persist into early Friday especially for the 20 to 60nm offshore zones. Another surface high pressure may setup along the northeast coast on Friday, potentially increasing wind speeds and wave heights across local waters.

EQUIPMENT

The Metter, GA, NOAA Weather Radio Station (WWH-25) will be offline from mid-morning Wednesday, October 7, through the afternoon of Thursday, October 8. The transmitter is being relocated.

CHS WATCHES/WARNINGS/ADVISORIES

GA...High Risk for Rip Currents from Tuesday morning through Tuesday evening for GAZ217-219-239-241. SC...High Risk for Rip Currents from Tuesday morning through Tuesday evening for SCZ148>151. MARINE...Small Craft Advisory from 5 AM Tuesday to 2 AM EDT Wednesday for AMZ340. Gale Warning from 5 AM Tuesday to 2 AM EDT Wednesday for AMZ360-362-380. Gale Warning from 5 AM Tuesday to 5 AM EDT Wednesday for AMZ364-382-384.