000 FXUS62 KCHS 191810 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 110 PM EST Tue Feb 19 2019 .SYNOPSIS... An unsettled pattern is expected as a series of frontal systems affect the area through early next week. && .NEAR TERM /THROUGH TONIGHT/... We're opting not to make any changes with this update. The forecast is close enough and the effort will be put into the afternoon package. Rest of Today: West-southwest flow will prevail through the day aloft, though the pattern will gradually amplify as a trough swings through the Four Corners region. At the surface, high pressure will continue to build in today as the 1036 mb parent high becomes centered near the Virginia Tidewater region late this afternoon. Moisture will increase from the south this afternoon and into the evening. Isentropic ascent will begin to spread in from the south and precipitation over the coastal waters will begin to expand northward. By sunset the forecast features 60 percent or greater rain chances along the Georgia coast into the southern South Carolina coast. Overcast skies will prevail today, and it just looks like a cool day overall. Highs today are expected to range from the low 50s across the north, to the upper 50s near the Altamaha River. Northeast winds will be persistent and at times gusty today, making it feel even cooler. Tonight: The coverage of precipitation will increase and spread northward through the night. Isentropic ascent will strengthen as a coastal trough sharpens along the coast. The forecast features 60 percent rain chances everywhere at one point or another, with a corridor of 80 percent or greater along the coast. By sunrise Wednesday the bulk of the rainfall is expected to be aligned along the Charleston County coast. The forcing is strong enough and there is enough moisture that rainfall amounts of half of an inch or greater will be possible along the coast by Wednesday morning. Temperatures will see a limited diurnal range through the overnight, with lows ranging from the low to mid 40s inland to the low 50s along the coast. Also of note, winds along the coast will likely see a an increase in winds during the first part of the overnight as the pressure gradient sharpens with the developing coastal trough. Northeast winds will likely gust into the 30-35 mph range at times, falling just short of Wind Advisory criteria. && .SHORT TERM /WEDNESDAY THROUGH FRIDAY/... The coastal trough will lift north of the area on Wednesday, taking with it most of the rain showers and allowing for considerable low-level warming. Highs across the southern two- thirds of the area should reach the upper 60s to lower 70s by late in the afternoon, however inland SC will remain in the 50s. Thursday will be unseasonably warm with high temps in the upper 70s to lower 80s with strong warm air advection. A few showers will be possible due to relatively moist low-levels and weak upper shortwaves moving through. Model guidance now shows a backdoor cold front sinking south through the area on Friday, with cool northeast flow developing across our northern zones during the day. Increasing isentropic ascent will yield moderate coverage of rain showers mainly over inland areas on Friday. We lowered high temps to the lower 70s far north, though farther south we still expect warm temps in the mid/upper 70s to lower 80s. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... The warm front will lift north of the area late Saturday, then a cold front will sweep through late Sunday. Cool high pressure will build in Sunday night through Monday, then shift northeast as Gulf low pressure moves into the area on Tuesday. && .AVIATION /18Z TUESDAY THROUGH SUNDAY/... 18Z TAFs KCHS: VFR through early this evening. Conditions will deteriorate to MVFR later this evening as showers associated with a coastal trough overspread the terminal. IFR is expected for a few hours overnight, but there is some uncertainty regarding the start time. The gusty northeast winds will continue through most of the night, then ease around daybreak. At that time the showers should be moving out of the area, allowing conditions to improve. KSAV: MVFR ceilings over the airport this afternoon are expected to gradually lower as showers associated with a coastal trough overspread the terminal this evening. IFR is expected to develop around midnight, and perhaps persist until the end of the TAF period. The showers should move out of the area before daybreak Wednesday. The gusty northeast winds will continue through most of the night, then ease around daybreak. Extended Aviation Outlook: Flight restrictions, mainly due to low ceilings, are likely Wednesday through Thursday morning. Another round of restrictions is expected Friday into Saturday as a front drops into the area. && .MARINE... Rest of Today: High pressure building in will cause gusty northeast winds in the 20-25 kt range with frequent gusts to 30 knots. Seas will build to 5-7 feet within 20 nm and 7-10 feet beyond. Tonight: There is good agreement that the tight pressure gradient will become further enhanced during the evening with the development of a coastal trough. This could push winds close to gale force for a period of time, though confidence is low and it still looks a bit marginal. Have opted not to issue a Gale Watch or Warning, but it will bear watching today. Will add a mention to the Hazardous Weather Outlook. Winds will begin to decrease from south to north after midnight as the pressure gradient relaxes. Seas will increase by a foot or so in the evening, then slowly decrease through sunrise Wednesday. Small Craft Advisories will remain in effect through the night. Seas will gradually subside Wednesday into Thursday after the flow becomes southerly and weakens. A brief SCA event is possible over the Charleston SC waters late Friday into Friday night as a northeast surge occurs behind a backdoor cold front. A more widespread SCA event is possible Sunday and Sunday night as strong southwest winds develop ahead of an approaching cold front. We included patchy fog over the nearshore waters late Wednesday night through Friday due to the likely development of sea fog during this period. Surface dewpoints in the low to mid 60s will be moving over cool shelf water in the upper 50s. && .TIDES/COASTAL FLOODING... The combination of astronomical influences and strong northeast winds along the coast will result in an elevated evening high tide. At least minor coastal flooding is expected along the southeast South Carolina and southeast Georgia coast, and Coastal Flood Advisories will be needed. The Wednesday morning high tide is likely to be the highest of the week given the persistent strong northeast winds leading up to it. At least moderate flooding is expected at Charleston and minor at Ft Pulaski, though it's not out of the question that a 1.5 ft anomaly could occur at Charleston which would approach major flood level there. The Wednesday evening astronomical high tide is the lower of the two for the day. Wind directions will have shifted to southerly by then, but residual anomalies could allow tides to approach advisory criteria at least at Charleston. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...Small Craft Advisory until 6 AM EST Wednesday for AMZ330. Small Craft Advisory until 10 PM EST Wednesday for AMZ352. Small Craft Advisory until 4 PM EST Thursday for AMZ350-374. Small Craft Advisory until 4 PM EST Wednesday for AMZ354. && $$ NEAR TERM... SHORT TERM...JRL LONG TERM...JRL AVIATION...BSH/JRL MARINE...BSH/JRL TIDES/COASTAL FLOODING...