939 FXUS62 KCHS 020209 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1009 PM EDT Thu Aug 1 2019 .SYNOPSIS... Inland low pressure and high pressure over the Atlantic waters is expected to prevail through the middle of next week. A weak low pressure center may pass offshore late weekend into early next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Late this evening: All has remained quiet with no convection across the forecast area. Made some minor tweaks to hourly grids, mainly for observations. Previous discussion continues below. Early this evening: Convection has pretty much run its course and radar imagery shows that you have to go north and northeast of the forecast area to find any ongoing activity. It looks like much of the overnight will be quiet and rain free but late tonight as we get closer to sunrise Friday rain chances will begin to increase from the south. Current precipitable water analysis shows the leading edge of a 2 inch or greater airmass poised just to the south. Models are in good agreement showing showers and thunderstorms developing along the leading edge of this deeper moisture and spreading into the coastal waters and the Georgia coast late tonight. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... Models continue to indicate that much of this period will be wetter as compared to last several days. The region will remain between a deep layer trough of low pressure from New England, southward across the southeast U.S., and ridge of high pressure centered well to the east over the Atlantic. Friday: The slug of tropical moisture currently located off of the north central Florid and southeast GA coast is expected to advect northward across the region. Given the weak upper level trough and sufficient moisture, expect scattered to numerous showers and thunderstorms. Relatively weak steering flow will contribute to the potential for locally heavy rainfall. High temperatures will be a near to slightly below normal given cloud cover/higher rain chances. Current forecast has high end chance PoPs, and may need to raise to likely levels if wetter model trends continue. Friday night, model consensus PoPs keep chance levels all night and even likely later at night over the Atlantic then moving into the area along and east of I-95 later night and toward morning. Lows ranging from the mid to upper 70s immediate coast, to lower to mid 70s else where. Saturday: Models hinting at a weak low/inverted surface trough over the nearshore Atlantic waters, which should further enhance/increase PoPs for the region. Have gone with likely PoPs by late morning and lasting through the afternoon. By late Saturday and Saturday night, the weak surface low pulls off to the northeast, taking the deeper moisture with it. Thus, have continued trending down PoPs to chance/slight chance through the night. Lows in the lower to mid 70s. Sunday: Deep layer moisture values decrease as the weak surface low over the Atlantic continues to pull away well to the northeast. However, the combination of the broad troughing of low pressure and still sufficient enough deep layer moisture, have kept high end chance PoPs most areas. The flow is expected to turn to southwest through a deeper layer, which may help provide conditions more conducive for training and the threat for locally heavy rainfall. High temperatures near normal, around 90 inland and mid to upper 80s closer to the coast. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... A broad trough of low pressure will persist over the area while high pressure remains offshore, maintaining fairly typical summertime conditions across the Southeast United States through the middle of next week. Light southerly winds will maintain ample moisture (PWATs around 1.5 to 1.75 inches) while sufficient sfc heating leads to high temps generally in the upper 80s near the coast to lower 90s inland each day. Given the pattern, chances of showers and thunderstorms are possible each day, while precip coverage should be less during overnight periods. Low temps should generally range in the lower 70s inland to mid/upper 70s near the coast. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... VFR conditions should prevail through the night at KCHS and KSAV. Shower and thunderstorm coverage is expected to increase from the south late tonight and early Friday morning, with showers perhaps impacting KSAV by the pre-dawn hours. Once the sun comes up Friday morning, showers and thunderstorms should develop quickly and could impact both sites during that time. Added in prevailing showers and VCTS at both sites, earlier at KSAV than at KCHS. Some model guidance is very aggressive with developing MVFR or lower ceilings late Friday morning and Friday afternoon. Confidence isn't high enough yet to go with this type of solution, but it is certainly something to keep an eye on. Extended Aviation Outlook: Friday and Saturday: Periods of flight restrictions will be possible in scattered to occasionally numerous showers and thunderstorms. By Sunday, the coverage of showers/thunderstorms is expected to be a little lower, but brief flight restrictions still possible. && .MARINE... Tonight: South to southeast winds will prevail as the subtropical high pressure holds well offshore. Speeds will generally remain 10 kt or less, although it could be locally higher in the Charleston Harbor as the sea breeze pushes inland this afternoon. Seas will average near 2 ft. Friday through Tuesday: No highlights are expected through the period, but rain chances are expected to increase, especially Friday and Saturday as a weak low pressure system and ample tropical moisture move across the waters. Winds will be east- southeast through Saturday, then veer to more south-southwest Sunday through Tuesday. Overall winds are expected to be 15 knots or less and seas 3 feet or less through the period. && .TIDES/COASTAL FLOODING... Tides look as though they have peaked and are on their way down. Will need to update in the next hour or so to cancel the warning/advisory when tide levels drop below flood stage. Elevated tides will continue Friday and through the weekend, due to a combination of astronomical and meteorological influences. Tide model guidance continues to show that the late day/evening high tides will reach high end moderate coastal flooding levels, and possibly as high as warning levels. In addition, if any heavy rainfall occurs around the time of high tide, this will increase the chance for urban flooding, especially for the Charleston Peninsula. Stay tuned to the latest tide level forecasts and the potential for additional Coastal Flood Advisories or Warnings through the weekend. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Coastal Flood Advisory until 1 AM EDT Friday for GAZ117-119- 139-141. SC...Coastal Flood Advisory until 1 AM EDT Friday for SCZ051-052. Coastal Flood Warning until 1 AM EDT Friday for SCZ048>050. MARINE...None. && $$ NEAR TERM...BSH SHORT TERM...RFM LONG TERM...DPB AVIATION...BSH/RFM MARINE...RFM/RJB TIDES/COASTAL FLOODING...