Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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720 FXUS62 KCHS 191555 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1155 AM EDT Wed Jun 19 2024 ...THE RISK FOR FREQUENT AND DANGEROUS RIP CURRENTS CONTINUES AT AREA BEACHES... .SYNOPSIS... High pressure will extend across the region today. A tropical wave will impact the Southeast U.S coast Thursday into Friday. && .NEAR TERM /THROUGH TONIGHT/... This Afternoon: No major changes were needed for the noon update. Isolated to scattered showers will continue to slowly consolidate along the Georgia and far southern South Carolina coast, including the Savannah Metro Area, through the afternoon. Instability is still being limited by a strong subsidence inversion. Temperatures look on track. Tonight: The TUTT approaches the northwest Bahamas, as it`s steered by an elongated anticyclone to our north. At the surface, we again lie underneath strong high pressure centered southeast of New England, as a surface trough in associated with the TUTT aloft moves toward the northwest Bahamas. there will be isolated to perhaps scattered showers within the deep easterly flow, but any t-storms look to be confined out near the Gulf Stream where there is a bit more CAPE and instability. It still looks like many interior places will drop into the mid and upper 60s with lighter winds developing and a somewhat dry boundary layer. But with winds remaining elevated near and along the coast, lows will be at least 5-10F degrees warmer. && .SHORT TERM /THURSDAY THROUGH SATURDAY/... Thursday: Aloft the region will be placed within the southern periphery of an anticyclone centered over New England. Just off the east coast of Florida a TUTT will be present. At the surface, high pressure will build into the local forecast area from the north, while an inverted trough will be present associated with the TUTT. Model soundings indicate there will be plenty of subsidence over the local forecast area, limiting precipitation in the afternoon hours. PoPs peak Thursday afternoon around 20-30%, with the highest chances across coastal southeast GA. Instability will be negligible, therefore have capped thunder probabilities at slight chance. High temperatures will be around normal, reaching into the upper 80s to near 90. A stream of moisture associated with the inverted trough and TUTT will begin encroaching on the forecast area Thursday night into Friday morning. PWATs around 1 inch on Thursday afternoon could approach 2 inches by Friday morning. Precipitation chances gradually increase Thursday night, as more showers are forecast to push onshore, especially across southeast GA. Overnight low temperatures are forecast to dip into the mid 60s far inland where conditions will likely remain dry and cloud free. Along the coastline with possible showers and increasing cloud cover, temperatures are only expected to drop into the low to mid 70s. Friday: The aforementioned stream of moisture will continue to feed into the forecast area as the inverted trough approaches closer to the southeastern coast. Aloft the region will remain along the southern periphery of an anticyclone. Instability Friday looks to be more supportive of thunderstorms. The best chance for showers and thunderstorms looks to be along the coastal counties, where PoPs are around 50-60% in the afternoon. Temperatures are forecast to reach into the upper 80s along the coast and low 90s further inland. Overnight lows will remain rather mild, with low 70s inland and mid to upper 70s along the coast. Saturday: The anticyclone aloft is forecast to shift further southward, centered over the southeastern states. At the surface the inverted trough associated with the TUTT will continue to approach the local forecast area, however it will likely be in a weakening state. PWATs will remain around 1.7 inches. Between the inverted trough and the local sea breeze, isolated to scattered showers and thunderstorms will again be possible in the afternoon. The highest chances will remain across southeast GA. Temperatures will begin to warm on Saturday, with highs in the mid 90s inland and low 90s at the coast. && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... A broad trough aloft will progress from the Great Lakes into New England, likely staying to the north of the local forecast area. The forecast area will likely be positioned along the eastern flank of an anticyclone aloft centered close to TX. At the surface the inverted trough will dissipate Sunday, however lingering moisture combined with the local sea breeze will produce isolated to scattered showers and thunderstorms. The main forecast highlight in the long term period will be the building heat. Temperatures on Sunday are forecast to reach in the mid to upper 90s away from the direct coastline, with close to 90 along the coast. Heat index values will likely reach from 102-105 with a few locations possibly around 107-108. The hottest day of the period will be Monday, with some inland locations pushing 100F. Heat index values are forecast to reach from 105-108. Heat Advisories may be required for Monday and possibly for Sunday. && .AVIATION /16Z WEDNESDAY THROUGH SUNDAY/... 19/18z TAF Discussion: KCHS/KJZI/KSAV: Risk for showers will translate away from KCHS and KJZI towards KSAV through the afternoon. Most of this should be out of both Charleston terminals by 18z. VCSH will continue to be highlighted at KSAV through about 21z. Otherwise, VFR through the period. Extended Aviation Outlook: Prevailing VFR. Flight restrictions will be possible at all terminals later in the week with showers and thunderstorms moving onshore. && .MARINE... Today and tonight: The local maritime area will be situated mainly under the control of impressive high pressure centered to the southeast of New England. There will be as much as about a 3 millibar spread north to south across the waters, leading to Small Craft Advisories that were already in place over the ocean. That gradient, plus the interaction of the land/sea interface will be enough for a Small Craft Advisory also impacting Charleston Harbor from late morning into at least early tonight. Winds across all waters will peak around 20 kt with gusts of at least 25 kt at times, and the very favorable onshore fetch will cause seas to reach 6 or 7 feet, with even waves up to 2 feet in the Charleston Harbor. Thursday through Sunday: Northeasterly winds 15 to 20 knots will persist across the local waters Thursday into Friday morning. Gusts may approach 25 knots at times. Winds Friday will remain out of the NE, however easing slightly to 10 to 15 knots. Conditions will continue to improve into Saturday, with winds shifting to the SE around 10 knots by Saturday night. Seas are forecast to build across the local marine zones, peaking Thursday with 5 to 6 ft across the nearshore waters and 7 to 8 ft across the 20-60 nm offshore GA waters. Small Craft Advisories are in effect for all waters outside the Charleston Harbor through Friday morning. Gusts in the Charleston Harbor may approach 25 knots, thus requiring a Small Craft Advisory as well. Seas will decrease Friday, with 3 to 4 ft forecast Saturday into Sunday. Rip Currents: There were at least 30-40 rip currents at Tybee yesterday, most of which were strong. This prompted closure of the waters to swimming, and it`s likely this will be the case again today. The agitated surf, strong long shore currents and the windy conditions will cause strong rip currents at all beaches. The High Risk has been maintained. A High Risk for rip currents has also been maintained for Thursday across all area beaches. An enhanced risk of rip currents will likely persist through the end of the week as long period swell impacts the region. High Surf: Guidance continues to show most breakers of 3-4 feet at the beaches today, with maybe an occasional 5 footer. This is not enough to warrant a High Surf Advisory. With similar winds over the ocean during tonight, the persistent onshore fetch could allow for 5 foot breakers to become more common, and a High Surf Advisory could be required. && .TIDES/COASTAL FLOODING... Tides are already more than a foot above astronomical levels, and with a continued moderate to strong easterly wind, and the Full Moon to occur Friday evening, those departures could grow even more. It`s possible that we could see minor coastal flooding over the coastal sections of Charleston and Colleton County with the evening high tides today, Thursday and maybe Friday. Tides elsewhere are forecast to remain below minor flood stage. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...High Risk for Rip Currents until 8 PM EDT this evening for GAZ117- 119-139-141. SC...High Risk for Rip Currents until 8 PM EDT this evening for SCZ048>051. MARINE...Small Craft Advisory until 1 AM EDT Thursday for AMZ330. Small Craft Advisory until 6 AM EDT Friday for AMZ350-352-354. Small Craft Advisory until 11 PM EDT Friday for AMZ374. && $$