Area Forecast Discussion
Issued by NWS Charleston, SC

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392 FXUS62 KCHS 170747 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 347 AM EDT Mon Jun 17 2024 .SYNOPSIS...
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A stationary front will dissipate across the area today, as high pressure builds from the northeast. High pressure will then continue to ridge in from offshore mid to late week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Today: Strong ridging aloft covers much of the eastern states, including the immediate area. Meanwhile at the surface, a stationary front will dissipate, as an elongated region of high pressure off New England extends overhead. The large scale subsidence, poor thermodynamics, and plenty of dry air between about 700 mb and 300 mb will likely prevent any convection from developing. However, it`s rare to not have any activity this time of year, so we carry a "silent" 10% POPs well inland this afternoon, just in case something is able to form along the inland penetrating sea breeze. Water vapor satellite imagery shows that dry air circulating in from the north and east around the anticyclone aloft, and this will allow for dew points to dip into the 60s for most communities. That along with modest easterly winds off the Atlantic will actually make it feel somewhat bearable, even though max temperatures still reach the upper 80s and lower 90s away from the ocean. 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.
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&& .SHORT TERM /TUESDAY THROUGH THURSDAY/...
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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.
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&& .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
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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.
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&& .AVIATION /07Z MONDAY THROUGH FRIDAY/...
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KCHS/KJZI/KSAV: Strong subsidence and considerable dry air between about 10K and 40K feet will result in little or no convection at any of the sites through 06Z Tuesday. Thus we are showing VFR conditions, with maybe a period of MVFR ceilings at any of the airports this upcoming morning due to the onshore flow. Gusty E winds will peak around 15-20 kt for all terminals this afternoon. 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.
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&& .MARINE...
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Today and tonight: The main feature will be an expansive area of a strong 1027-1029 millibar high pressure system centered off New England that covers the local waters. There`s a decent gradient in place, and that along with sea breeze influences during the afternoon and evening, and nocturnal low level jetting, E winds will be up near 15 kt and gusty through the period. Seas will work their way up to 3 or 4 feet within 20 nm due to the favorable onshore fetch, while 4 to 5 feet will be reached on the Georgia waters 20-60 nm out. 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.
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&& .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM... SHORT TERM... LONG TERM... AVIATION... MARINE...