Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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833 FXUS62 KCHS 171755 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 155 PM EDT Mon Jun 17 2024 .SYNOPSIS... High pressure will extend across the region through early next week. A tough of low pressure could approach the Southeast U.S coast by late this week. && .NEAR TERM /THROUGH TONIGHT/... This Afternoon: Aloft, a large ridge will remain centered across the Southeast and Mid-Atlantic states, favoring large scale subsidence across the local area. At the sfc, high pressure centered across the western Atlantic off the Mid-Atlantic and Northeast Coast will extend south across the local area, providing an onshore flow throughout the day. Despite the onshore flow, dry air depicted on water vapor imagery favors rain-free conditions across most coastal areas and for much of southeast South Carolina. However, inland locations across southeast Georgia could experience a few showers this afternoon where adequate moisture and SBCAPE between 1500-2000 J/kg resides. Subsidence aloft will limit the strength of convection across the noted area, but a few showers (or perhaps a thunderstorm) could produce gusty winds given strong low-lvl lapse rates around 8 C/km and DCAPE around 1200 J/kg. 1000-850mb thicknesses along with ample sunshine favor high temps in the upper 80s closer to the coast to lower 90s inland. Tonight: There is very little change in the pattern, both surface and aloft, with deep high pressure firmly in control. With the dew points generally down in the 60s, winds slackening off through the night, and no worse than mostly clear or partly cloudy skies, minimum temperatures look to drop to 65-70F well inland, lower and middle 70s closer to the Atlantic. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... High pressure both aloft and at the surface will be centered over New England, extending into the local forecast area from the NE on Tuesday. This pattern will persist into Wednesday, when the centers of high pressure begin to shift eastward, taking up residence closer to Bermuda. Subsidence aloft will begin to break down as the high pressure moves further offshore. A weak coastal trough is expected to form along the southern periphery of the ridging aloft, leading to isolated to scattered showers and thunderstorms Tuesday and Wednesday afternoons. Precipitation will likely be confined to the coastal zones of extreme southern SE SC and SE GA. Precipitation chances will gradually increase through the week, as well as an increase in areal coverage, as persistent onshore flow brings an influx of moisture into the region. Temperatures are expected to be around normal, to maybe even slightly below normal. The forecast features highs in the upper 80s to low 90s and overnight lows in the upper 60s to low 70s. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... Subsidence will continue to diminish aloft with the retreating high pressure at the surface and aloft. The forecast will trend back towards a more typical summertime pattern, with isolated to scattered showers and thunderstorms in the afternoon hours. Moisture is forecast to begin streaming into the region late week as a possible low pressure lingers off the east coast of Florida. This additional moisture will help to enhance afternoon showers and thunderstorms, especially across southeast GA later in the week. Temperatures are expected to remain near normal. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... Prevailing VFR conditions are expected at CHS/JZI/SAV terminals through 18Z Tuesday. However, brief MVFR cigs are possible late tonight/early Tuesday with an onshore wind in place, mainly at the SAV terminal. Confidence remains too low to include in the latest 18Z TAF issuance. Otherwise, gusty east winds (15-20 kt) are expected between 18Z-01Z at the terminals today, followed by another round of gusty east winds (13-18 kt) at the terminals starting around 1430Z and persisting through 18Z Tuesday. Extended Aviation Outlook: Prevailing VFR. Brief flight restrictions are possible in afternoon showers/thunderstorms Tuesday and Wednesday, especially at KSAV. Chances of flight restrictions increase at CHS/JZI/SAV terminals later in the week with showers and thunderstorms moving onshore. && .MARINE... This Afternoon and Tonight: High pressure will remain the dominant weather feature, extending across the region from the north and enhancing the pressure gradient across local waters. The gradient along with an afternoon seabreeze circulation and nocturnal low-lvl jetting will favor easterly winds between 15-20 kt this afternoon, then around 10-15 kt with gusts to around 20 kt at times overnight. Seas will also slowly build during the period due to a prolonged onshore fetch. In general, seas should build to 3-4 ft across nearshore waters and 4-5 ft across offshore Georgia waters, largest overnight. Tuesday through Friday: Generally, high pressure will prevail over the local waters through the period. With high pressure extending into the region from the northeast and a developing low pressure off the east coast of FL the pressure gradient is expected to pinch Tuesday into late week. This pinched gradient will likely result in E winds 15 to 20 knots with gusts to 25 knots and seas building to as high as 5 to 6 ft across the nearshore waters and 8 to 9 ft across the 20-60 nm offshore GA waters. Small Craft Advisories will likely be needed for most, if not all, marine waters beginning as early as Tuesday night for the 20-60 nm offshore GA waters. Rip Currents: A continued onshore wind that averages around 15 mph, plus a small swell will produce a Moderate Risk of rip currents at the area beaches today. A Moderate Risk for rip currents will remain in place through Tuesday with increasing swells. At least a Moderate Risk for rip currents will likely continue for all beaches through the middle of the week as swell energy continues to increase ahead of a low pressure approaching the Southeast United States late week. && .EQUIPMENT... Our office phones are down, with the telephone company working on correcting the problem. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM... SHORT TERM... LONG TERM... AVIATION... MARINE...