Area Forecast Discussion
Issued by NWS Charleston, SC

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000 FXUS62 KCHS 031006 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 606 AM EDT Sat Jun 3 2023 ...COASTAL FLOODING LIKELY AROUND THE EVENING HIGH TIDE THROUGH MONDAY... .SYNOPSIS...
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A weak cold front will drop south through the area tonight. High pressure returns for the first half of next week. Another front could move through the area towards the middle of next week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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No major changes were made for the sunrise update. A few showers could brush the beaches of Charleston County over the next few hours, but this activity will tend to dissipate as it reaches the coast. Today: Friday`s Rex Block will finish its transition to an Omega Block across the CONUS today. This will keep surface features across the Southeast U.S. fairly static with high pressure holding firm across the Carolinas into eastern Georgia and Tropical Storm Arlene slowing meandering south over the eastern Gulf of Mexico while weakening. It will be another fairly quiet day across Southeast South Carolina and Southeast Georgia. Deeper moisture, higher mean PWATs and no capping aloft per modified soundings could promote a bit more in the way of convection this afternoon, but activity is still expected to remain somewhat limited with little in the way significant synoptic forcing mechanisms in place. Coverage should remain in the isolated to perhaps scattered category with the better chances for deep, moist convection holding over Southeast Georgia, especially along/south of the I-16 corridor where a bit more instability and a ribbon of higher quality moisture will be found. 10-30% pops look reasonable for this afternoon into early this evening. Areas adjacent to the southern Midlands and CSRA may not see much, if any, shower activity as guidance shows a sharp moisture gradient setting up in this area. Highs will peak mid-upper 80s away from the coast with mid-upper 70s at the beaches. Tonight: Any lingering convection will quickly wane after sunset with the loss of insolation. Dry conditions will prevail overnight as an weak, ill-defined backdoor cold front/wind shift drops south through the area and the inland high pressure wedge is reinforced. Some clearing will occur this evening with stratocumulus expanding inland from off the Atlantic overnight as the front drops south. Lows will range from the mid 60s across the far interior to the upper 60s/lower 70s along the beaches and Downtown Charleston.
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&& .SHORT TERM /SUNDAY THROUGH TUESDAY/... Sunday: Weak mid-level troughing will prevail over the Southeast U.S. in the morning. It`s expected to gradually weaken further with time. A cold front will be located near the Altamaha River at daybreak. It`s forecasted to continue moving south and away from our area during the day, while drier High pressure gradually builds in from the north. Models still indicate there`s a risk of an isolated shower or thunderstorm along our coastal GA counties through the Altamaha River through the afternoon, so we maintained mainly slight chance POPs in these location. Otherwise, most locations are expected to remain dry with partly sunny skies. Cooler air advection within northeast winds will cause high temperatures to be several degrees below normal. Low-level thickness values and perhaps more clouds than sun support highs near 80 degrees across our SC counties, and the lower to maybe middle 80s across our GA counties. It will also be breezy in the afternoon, especially at the beaches. The evening and overnight will be dry with decreasing clouds. Temperatures will be noticeably below normal with lows ranging from the mid to upper 50s far inland to the low/mid 60s along the immediate coast. Monday: The weak mid-level trough over the Southeast U.S. will continue to dissipate. However, a trough over the Northeast U.S. will strengthen, yielding NW flow over our area. At the surface, High pressure centered just to our north in the morning will move south with time. This will keep a front and the remnants of Arlene well to our south. The High will dominate our weather, bringing unseasonably dry conditions with mostly sunny skies. Highs will remain a few degrees below normal, but still peak in the lower to mid 80s, except cooler at the beaches. The dry conditions and mostly clear skies continue into the evening and overnight hours. This will lead to lows mainly in the 60s. Tuesday: A strong trough will remain over the Northeast U.S., yielding NW flow over our area. Surface High pressure over the Southeast U.S. will shift offshore in the afternoon. As it moves away, the sea breeze could generate isolated convection in the afternoon. But most places could end up remaining dry. Highs will rise to above normal for a change, with most locations topping out around 90 degrees, except cooler at the beaches. && .LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/... Mid-level troughing over the Northeastern U.S. will continue to gradually creep southward through Friday. But most of it`s energy should remain just north of our area. At the surface, a cold front is expected to move south into our area on Wednesday. It should become stationary and remain in place over or near us through Friday. This will generate convection each afternoon. But the exact location of the front will determine which areas have more convection. Temperatures will be near normal. && .AVIATION /10Z SATURDAY THROUGH WEDNESDAY/...
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03/06z TAF discussion: KCHS/KJZI: The risk for MVFR cigs is diminishing. VFR will prevail. Winds could get a little gusty at KJZI by mid- afternoon as winds veer more easterly. Some patchy MVFR cigs could form prior to daybreak Sunday as stratocumulus moves inland from off the Atlantic behind a weak backdoor cold front. KSAV: VFR will prevail. Isolated showers will likely be lurking about early-mid afternoon, but impact probabilities are too low to justify a mention at this time. Extended Aviation Outlook: A cold front could bring flight restrictions and gusty NE winds on Sunday. Mainly VFR will prevail afterwards. There will be low probabilities of flight restrictions during the middle of next week due to afternoon/evening convection.
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&& .MARINE... Through Tonight: Northeast winds will average around 15 kt through the day with seas 2-4 ft, building to 3-5 ft. Overnight, a northeast wind surge will work south behind a backdoor cold front. By daybreak, northeast winds will reach 20-25 kt with gusts to 30 kt over the South Santee-Edisto Beach nearshore leg with 15-20 kt with gusts to 25 kt elsewhere. Seas will build 4-6 ft over the South Santee-Edisto Beach nearshore leg to 3-5 ft in the Edisto Beach-Savannah nearshore and Georgia offshore legs with 2-3 ft in the Savannah-Altamaha Sound nearshore leg. A Small Craft Advisory has been issued for all legs except Charleston Harbor beginning at 4 AM. Sunday: A cold front will be located near our extreme southern GA waters at daybreak. It`s forecasted to move south, away from our area during the day. Meanwhile, High pressure will gradually build in from the north. The combination of an elevated surface pressure gradient and cooler air advection over the waters will yield gusty NE winds and steep, wind-driven waves. Small Craft Advisories will be in effect for all of the ocean waters. Additionally, Charleston Harbor may need an advisory for wind gusts during the day. Winds and seas will start to trend lower overnight as the pressure gradient levels off and the cool advection wanes. But conditions will remain high enough for the advisories to continue. Monday: High pressure will approach from the north, while a front and the remnants of Arlene remain well to our south. The High will be the dominant feature for our area, causing elevated NE winds in the morning to ease during the day, with seas subsiding as well. The Small Craft Advisories for the waters within 20 nm should end by late afternoon. However, the advisory for the GA waters beyond 20 nm should persist until around midnight. Wind and seas will continue to trend lower during the evening and overnight. Tuesday and Wednesday: High pressure is expected to be centered to our south on Tuesday, then shifting away by midweek. At that time, another front could approach from the north, possibly bringing elevated winds and seas. Rip Currents: Persistent, strong NE winds will be generating elevated seas, with a somewhat onshore component, more notably for our GA beaches. A Moderate risk of rip currents is in effect for all of our beaches on Sunday. It`s not out of the question this risk may need to be raised if winds/seas are higher than expected. The risk of rip currents persist on Monday. && .TIDES/COASTAL FLOODING... Charleston/Coastal Colleton: Tide levels in the Charleston Harbor will make a run for the 8.0 ft MLLW major flood threshold for this evening`s high tide. A Coastal Flood Watch has been posted to account for this possibility. The watch will be upgraded to a Coastal Flood Advisory or Coastal Flood Warning later today as the total water forecast is further refined based on this morning`s tide trends. Significant saltwater flooding can be expected at this level across much of the coast of Charleston and Colleton Counties, including areas around Charleston Harbor. Road closures are likely across much of Downtown Charleston at this level and saltwater will approach or even flood the lower levels of some structures. Similar conditions will be experienced elsewhere up and down the coast. The backside of Edisto Beach along Big Bay Creek is especially vulnerable at 8.0 ft MLLW. Levels will peak near or just above major flood thresholds for Sunday evening and possibly again Monday evening. Additional Coastal Flood Watches and Warnings may be needed. Beaufort County south to McIntosh County: Tide levels at Fort Pulaski are expected to peak well into the minor flood level for this evening`s high tide and could even approach moderate flood stage. At the upper portion of the minor flood level, water will approach or even encroach onto portions of Highway 80 heading to Tybee Island. Some saltwater flooding could also occur along the backside of Tybee Island and Fripp Island and in parts of Darien along Darien Creek. Moderate flooding is possible with the Sunday evening high tide and again Monday evening. Right now, it appears levels will remain below major flooding thresholds. A Coastal Flood Advisory will likely be issued for this area later today. Additional Coastal Flood Advisories will be needed Sunday and possibly Monday. Tidal Berkeley: Minor flooding typically occurs across parts of southern Berkeley County, especially in Daniel Island, when tide levels reach 8.0 ft MLLW in the Charleston Habor. A Coastal Flood Advisory may be needed for this area this afternoon and possibly again Sunday and Monday evenings. && .CHS WATCHES/WARNINGS/ADVISORIES...
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GA...None. SC...Coastal Flood Watch from 6 PM EDT this evening through this evening for SCZ049-050. MARINE...Small Craft Advisory from 4 AM Sunday to 3 PM EDT Monday for AMZ350-352-354. Small Craft Advisory from 4 AM Sunday to midnight EDT Monday night for AMZ374.
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