Area Forecast Discussion
Issued by NWS Charleston, SC

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000 FXUS62 KCHS 212000 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 400 PM EDT Sat May 21 2022 .SYNOPSIS...
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Warm and somewhat humid conditions will persist through the next several days. Along with a few weak weather systems moving through the region, will lead to periodic showers and thunderstorms through late next week.
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&& .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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This Evening and Tonight: High pressure will prevail across the western Atlantic with a mid-upper lvl ridge axis nudging further offshore as pockets of mid-lvl energy traverse across the Southeast United States. Deep moisture advecting across the region within a south-southwest sfc flow will continue to favor scattered to potentially numerous showers and thunderstorms into early evening hours, a few of which could be strong and/or marginally severe within an environment displaying MLCAPE up to 2500-3000 J/kg and DCAPE around 800-900 J/kg, especially if thunderstorms are able to interact with outflow boundaries and/or the inland moving sea breeze circulation. Greatest chances of thunderstorms should occur along and west of the I-95 corridor with isolated instances of damaging winds and hail being the primary concerns, but some areas could see brief heavy rainfall due to slower moving thunderstorms. The SPC currently marks the entire area in a Marginal Risk of severe weather. Shower and thunderstorm activity could linger for a few hours after sunset this evening with ample moisture, mid-lvl energy aloft, and remnant boundaries in place. However, diurnal heat loss will eventually take over, resulting in convection weakening/diminishing by midnight. The rest of the night should remain dry with light/calm winds in place. Temps will remain mild, only dipping into the upper 60s inland to lower 70s near the coast.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
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Pattern Synopsis/Forecast: Larger scale troughing will remain in place across the northern/central Plains into the Great Lakes through this period, while larger scale ridging, and a warm and fairly moist/unstable airmass holds across the SE states into the Atlantic. A weakening surface cold front will slowly press into the inland Carolinas and Georgia heading into Monday before stalling across the region. Larger scale forcing for ascent will be notably absent through the balance of the weekend. Thus daily convective trends will continue to be modulated by mesoscale features, convective outflows or small scale mcv`s interacting with the sea breeze, with the usual tendency for higher pops during the day, waning at night. Slightly better larger scale forcing for ascent might arrive on Monday with some hint of a wave riding along the stalled boundary, potentially bringing some increased rain chances and needed higher QPF totals. But the upshot, periodic chances for showers and some thunderstorms will persist, largely tied to the diurnal heating cycle. Overall severe weather potential will remain on the lower side owing to weaker wind profiles. That said, a few brief pulse storms could produce an isolated wind/hail threat, and slow moving convection could lead to localized heavy rainfall. Otherwise, temperatures will continue to run at or a little above normal through Monday, perhaps cooling down slightly Tuesday with the boundary, for at least parts of the forecast area.
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&& .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
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Upper level ridging, warm and somewhat humid conditions remain in place across the SE states through the midweek timeframe, along with periodic chances for showers storms. Meanwhile, a bit deeper and progressive upper level trough is expected to swing through the Mississippi River Valley and across the eastern CONUS, driving a stronger cold front through the region for the end of the work week. This may bring a bit higher rainfall chances and a bit more widespread rainfall amounts to the region during that time. Still a ways out yet with the usual timing uncertainties, and thus plan to maintain our higher chance forecasts for now. High pressure and modestly drier air is looking to build into the region for the start of next weekend.
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&& .AVIATION /20Z SATURDAY THROUGH THURSDAY/...
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Showers and thunderstorms are expected to develop across the area, likely impacting all terminals for a few hours this evening. At this time, latest trends suggest a few showers to impact CHS and JZI terminals late evening while thunderstorms occur at the SAV terminal late afternoon into early evening. Tempo MVFR conditions are possible during showers/thunderstorms, before activity shifts inland and/or weakens this evening. VFR conditions should then prevail at all terminals tonight and through Sunday morning. Extended Aviation Outlook: Periodic restrictions remain possible at the terminals through the upcoming week, as a weak cold front stalls over the area bringing a higher than normal chance for showers and some thunderstorms, especially each afternoon and evening. Could also see a bit better chance for at least MVFR ceilings Monday night into Wednesday, especially at KCHS and KJZI which are more likely to be on the north side of the front. Another stronger cold front will swing into the region Thursday into Friday, maintaining the risk for periodic flight restrictions.
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&& .MARINE...
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This Evening and Tonight: Showers and thunderstorms will impact portions of the coastal waters this evening, mainly off the Georgia coast, a few of which could be strong with winds in excess of 34 kt. Outside thunderstorms, south/southwest winds will prevail across local waters through tonight. Wind speeds will remain highest along the land/sea interface this evening, generally up to 15-20 kt. A few isolated gusts to 25 kt winds are possible, mainly near the Charleston Harbor. However, the duration of higher gusts should fall short of the need for a Small Craft Advisory. Expect winds to weaken and slowly veer to south-southwest later tonight, generally remaining at or below 15 kt. Seas are expected to remain in the 2-4 ft range. Sunday through Thursday: Atlantic high pressure will prevail across the southern SC/northern GA Atlantic nearshore waters into early next week before a cold front likely pushes into the area Monday night and lingers into Wednesday. This will lead to varying wind directions depending on the timing and location of the front, although overall winds and seas will remain below Small Craft Advisory. A bit stronger southeasterly winds may develop through the coastal waters for the mid to late week period as a strong cold front approaches from the west. However, at this juncture, winds and seas will remain below headline criteria.
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&& .CLIMATE... May 21 Record High Min Temperatures: KCHS: 74/last set in 2001 KCXM: 78/1998 KSAV: 74/last set in 2017 && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...DPB SHORT TERM...TBA LONG TERM...TBA AVIATION...DPB/TBA MARINE...DPB/TBA CLIMATE...

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