Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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463 FXUS62 KCHS 061004 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 604 AM EDT Sun Oct 6 2024 .SYNOPSIS... High pressure will prevail today. A cold front will push across the area Monday night into Tuesday as Tropical Storm Milton strengthens over the Gulf of Mexico. The center of Milton is forecast to track east across Florida on Wednesday as a hurricane, tracking over the western Atlantic Wednesday night into Thursday. High pressure should build across the region by late next week. && .NEAR TERM /THROUGH TONIGHT/... A solid ribbon of light to moderate rain continues to stream into McIntosh County. Near term guidance suggests this will linger for a few more hours. Pops were raised to 80% for this area with the sunrise update. Today: The synoptic pattern has not changed much over the past 24 hours with the region positioned beneath a large mid-level weakness along the northern flanks of weak subtropical ridging centered over Florida and the eastern Gulf of Mexico. At the surface, broad, elongated 1030 mb high pressure centered over Newfoundland, Canada, continues to extend south along the eastern U.S. with its southern flanks expanding across the Deep South and the Southeast States. A weak coastal trough noted offshore near the west wall of the Gulf Stream has shown signs of washing out over the last day or so, but remains defined enough to support a weak convergence field along the western side of the trough axis. This is helping to support scattered to numerous showers over the Georgia coastal waters. This pattern will change little this morning with the best focus for showers moving onshore holding along the middle Georgia coast south into northeastern Florida. Rain chances will be maximized in this area this morning with pops ranging from 20-60% south of a Glennville to Ossabaw Island, highest across Darien and Sapelo Island. Given the lack of synoptic forcing, the risk for tstms is likely too low to justify a mention today, despite some weak surface-based instability noted. Rain chances across coastal Georgia will diminish as the afternoon progresses in response high pressure nosing even farther to the south. Dry weather will persist elsewhere across Southeast South Carolina and Southeast Georgia with near zero pops north of I-16 corridor. Highs today will range from the lower-mid 80s inland with upper 70s/near 80 at the beaches and far south around Darien where rainfall will tend to limit temperatures a bit. Tonight: High pressure will build farther to the south tonight as a cold front approaches from the northwest. A few showers could linger across McIntosh County during the early evening, but this activity will wane quickly after sunset. The coastal trough offshore will have mostly washed out by tonight, becoming mostly damped by the expanding northeast flow induced by high pressure building to the south. Dry conditions will dominate overnight as high clouds thin and push offshore. Lows will range from the lower 60s well inland to the lower 70s at the beaches. A few upper 50s could occur, mainly over the Francis Marion National Forest and areas north of Lake Moultrie. && .SHORT TERM /MONDAY THROUGH WEDNESDAY/... Broad troughing will prevail Monday in the upper levels, extending from just east of the Great Lakes down into the Mid- Atlantic region. At the surface high pressure will prevail across the local forecast area on Monday, with a cold front forecast to push through the region Tuesday/Tuesday night. In the Gulf of Mexico, Tropical Storm Milton is forecast to develop into a hurricane early in the week and track eastward towards the Florida Peninsula. With the large scale circulation from Milton the aforementioned cold front could become stalled in the vicinity of the forecast area. Despite FROPA, dry conditions have been maintained through the short term period. High temperatures are forecast to be in the 80s on Monday and Tuesday, with mid 70s on Wednesday post-FROPA. Low temperatures Monday and Tuesday nights will be in the 60s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... Moisture will begin to lift northward into the forecast area Wednesday night, with PWATs increasing to near 2 inches across SE GA. Many forecast details in the long term are dependent on the placement, timing, and strength of Hurricane Milton. The latest forecast from the National Hurricane Center has the center of Milton tracking across central Florida Wednesday/Wednesday night and pushing into the western Atlantic on Thursday. The current forecast features slight chance to chance PoPs Wednesday night into Thursday. However, a slight shift northward would be cause for an increase in PoPs. Similarly, a shift southward would decrease PoPs. These details will need to be ironed out as more guidance comes in and the event comes closer. Regardless of the exact positioning of Milton, cloudy conditions are expected as well as gusty NE winds, especially near the coast. High temperatures should be limited to the mid to upper 70s. Milton is forecast to exit the region Thursday, with conditions rapidly improving on Friday and into the weekend as high pressure builds into the region. Dry conditions will prevail, with temperatures in the 70s. && .AVIATION /10Z SUNDAY THROUGH THURSDAY/... 06/12z TAF Discussion: KCHS/KJZI/KSAV: VFR through 07/12z. Extended Aviation Outlook: Flight restrictions are possible mid-week as Hurricane Milton crosses the Florida Peninsula and emerges off the SE U.S. coast. Additionally, periods of gusty NE winds will be possible mid-week. && .MARINE... Today: The pressure gradient between the coastal trough offshore and high pressure to the north will gradually waned today as the coastal trough starts to become increasingly overwhelmed by the broadening field of northeast winds. Winds will average 15 kt with gusts to 20 kt for much of the day with seas building 3-5 ft within 20 NM and 5-6 ft over the Georgia waters from 20-60 NM offshore where a Small Craft Advisory is in effect. Tonight: Northeast winds will continue to diminish overnight as high pressure builds south and a cold front approaches from the northwest. Speeds will average 10 kt from South Santee-Edisto Beach out 20 NM, 10-15 kt from Edisto Beach to Altamaha Sound out 20 NM and as high as 15 kt with gusts to 20 kt over the Georgia waters from 20-60 NM offshore. Seas 3-5 ft will persist within 20 NM and 5-6 ft over the Georgia waters from 20-60 NM where, again, a Small Craft Advisory continues. Monday and Tuesday: High pressure will prevail across the marine waters on Monday with a cold front progged to approach the waters on Tuesday/Tuesday night. Tropical Storm Milton is forecast to develop into a hurricane as it treks eastward across the Gulf of Mexico. The large circulation around Milton will likely cause the approaching cold front to stall in the vicinity of the forecast area. Northeast winds will begin to surge into Tuesday as the pressure gradient becomes pinched between the cold front and the circulation around Milton. NE winds will increase to around 15 to 20 knots Tuesday, with gusts around 25 knots. Seas are forecast to build to 3 to 4 ft across the nearshore waters, with 5 to 6 ft across the 20 to 60 nm offshore GA waters. By Tuesday, a Small Craft Advisory will likely be needed for all marine zones. Wednesday and Thursday: Conditions across the marine zones will deteriorate quickly with tropical storm conditions possible. The forecast will be largely dominated by the timing, placement, and strength of Hurricane Milton. However, gusty NE winds are likely across the marine waters, possibly gusting to around 50 knots across the GA waters with it`s closest passage to the coast. Seas are forecast to build to 15 to 20 feet in the 20 to 60 nm offshore GA waters. Friday: Conditions should begin to improve on Friday as Hurricane Milton progresses further into the Atlantic and away from the east coast. Gusty NE winds around 25 knots will still be common, and while seas will begin to diminish they are still forecast to be 5 to 7 ft along the nearshore waters and 8 to 10 ft across the 20 to 60 nm offshore GA waters. Rip Currents: Morning buoy reports show a 2 ft underlying easterly swell of 15-17 seconds prevailing across the waters. This swell energy was generated by distant Hurricane Kirk several days ago and will remain in place through the day. Local rip current calculations support a solid high rip current risk across the Georgia beaches, but is teetering right at the moderate/high risk thresholds across the South Carolina beaches. Given this swell is hurricane induced, a more aggressive approach is typically favored and is supported by previous hurricane swell events over the past several years. For this reason, a high rip current risk is being highlighted for all beaches into this evening. Conditions supporting a high risk will persist into Monday. High Surf: The risk for high surf with breaking waves of 5 ft or higher along with significant beach erosion will increase later this week as Milton emerges off the Florida East Coast. A High Surf Advisory could be needed for the beaches by mid-week. && .TIDES/COASTAL FLOODING... Tide levels in the Charleston Harbor are expected to peak right around 7.0 ft MLLW for the late morning high tide. A Coastal Flood Advisory may be needed later this morning. Coastal flooding is also possible during high tides from Tuesday through Thursday morning along the entire coast. Coastal flooding appears most likely as Milton tracks across FL to the western Atlantic Wednesday into Thursday. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...High Risk for Rip Currents through this evening for GAZ117-119-139- 141. SC...High Risk for Rip Currents through this evening for SCZ048>051. MARINE...Small Craft Advisory until 6 AM EDT Friday for AMZ374. && $$