Area Forecast Discussion
Issued by NWS Charleston, SC

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000 FXUS62 KCHS 300731 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 331 AM EDT Mon Mar 30 2020 .SYNOPSIS...
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A cold front will pass offshore early this morning, and is followed by a weak pressure pattern today into tonight. Low pressure will then cross the area Tuesday into Tuesday night, followed by high pressure for mid to late week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Pre-dawn: A weak and dry cold front will pass into the ocean, accompanied by scattered-broken stratocumulus, and scattered- broken cirriform clouds. Given that there isn`t much in the way of cool air behind the front, temps will begin the day far above climo. For today: The cold front will eventually stall out near the Georgia/Florida line, with a weak surface pressure pattern in place across the local area. A trough to the lee of the Appalachians will support a deep and dry west-southwest flow, while a zonal flow dominates aloft. As mixing heights climb throughout the day, dew points will plummet into the 40s inland from the coast. With a weak downslope flow, a dry lower and middle atmosphere and 850 mb temps that are 14-15C, we look for max temps to peak in the lower 80s northwest and north tier, with mid and upper 80s most elsewhere inland from the immediate coast. We didn`t go quite as warm as the "pure" low level thickness forecast since there will be varying amounts of broken cirriform clouds traversing the area. Tonight: A stationary front will remain to the south, as low pressure travels quickly eastward from northern Texas into the lower Mississippi Valley. To the north we find the southern extension of high pressure poking in late from the lee of the mountains. Mid and high level clouds will steadily increase, so we didn`t go as low for temps as the MOS guidance would suggest, equating to min temps that are close to 10F above normal.
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&& .SHORT TERM /TUESDAY THROUGH THURSDAY/...
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Tuesday will be the most active day of the coming week. A potent mid level trough will swing into the eastern U.S. through the day. As this occurs, surface low pressure will approach from the west and eventually track over the area in the afternoon and evening. Increasing moisture (noted by PWats of over 1.6 inches) and forcing for ascent will provide focus for showers and some thunderstorms. Most areas are expected to receive a half of an inch of rain on average through the event. Attention then turns to the severe weather potential. 0-6 km shear is over 50 knots, which will certainly promote storm organization. The limiting factor will be the instability. Mid level lapse rates are unimpressive and CAPE values are marginal. The most favorable ingredients will be across Georgia zones, especially south of I-16, which is where SPC Day 2 Outlook highlights a Slight Risk of severe weather. Areas further north near the Charleston tri-county will reside in a more stable environment, so the severe threat will be lesser. The primary threat within strong/severe storms are damaging wind gusts and perhaps a tornado. Otherwise, temperatures will peak in the 70s, around 80 near the Altamaha. The bulk of rainfall will push off the coast late Tuesday evening, with any lingering showers diminishing by Wednesday morning as drier air filters in. Cold advection will bring lows closer to normal. The low will pull away from the area on Wednesday as high pressure expands into the region. Residual low level moisture will keep clouds around for the first part of the day, but cloud cover will diminish with time. Noticeably cooler temperatures are expected, with highs peaking in the mid to upper 60s. Lows Wednesday night near normal. High pressure will persist through Thursday. Dry conditions are expected with plenty of sunshine. Highs will range from the upper 60s in the north to mid 70s south.
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&& .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/...
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Relatively quiet weather expected late week into the weekend as high pressure remains the dominant feature. A couple models hint that a weak front could approach/cross late in the period, but this has been trending later each day. Rain chances overall will remain pretty low, but as moisture returns over the weekend a few showers can`t be ruled out. Temperatures will be near to slightly above normal.
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&& .AVIATION /07Z MONDAY THROUGH FRIDAY/...
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VFR through 06Z Tuesday at both CHS and KSAV. Extended Aviation Outlook: Flight restrictions in low clouds and showers/thunderstorms are likely Tuesday evening into Tuesday night as low pressure crosses the area. VFR is expected to return Wednesday morning and will prevail through late week.
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&& .MARINE...
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Today: A cold front will pass into and through the waters before daybreak, and is followed by weak high pressure throughout the upcoming day. Winds will become W-NW at no more than 10 or 12 kt for the daylight morning hours, before light sea breeze influences develop in the afternoon. Seas will average 2 or 3 ft. Tonight: We find the front wavering near the Florida waters in advance of low pressure moving through Texas toward the lower Mississippi Valley. Winds will begin the night from the S or SW at or below 10 kt, veering to W`erly after midnight, then finally to NW and N late as the leading edge of high pressure tries to nose in from the north. Seas will average just 1-2 ft. Tuesday through Saturday: Low pressure will track into and over the area Tuesday into Tuesday night. Winds and seas will increase as this occurs, and Small Craft Advisories will be possible for portions of the waters Tuesday evening into Wednesday morning. The low will lift away from the area on Wednesday, allowing conditions to improve. High pressure will then return for the latter half of the week. No additional marine concerns are anticipated.
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&& .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM... SHORT TERM...ETM LONG TERM...ETM AVIATION... MARINE...

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