371 FXUS62 KCHS 291804 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 204 PM EDT Fri Mar 29 2019 .SYNOPSIS... Warm high pressure will prevail into Sunday. A cold front will then move through late Sunday, followed by a coastal storm which will produce rain and below-normal temperatures Monday and Tuesday. Warmer and drier high pressure will then build over the region mid to late week. && .NEAR TERM /THROUGH TONIGHT/... Early this afternoon: No changes needed to the going forecast. Previous discussion continues below. Late this morning: Patchy fog/stratus at sunrise has been somewhat slow to dissipate this morning, especially along the Georgia coast. This likely has to do with the fact that from the 12z CHS RAOB, winds up to almost 3 kft were either calm or less than 5 knots. Therefore, the main dissipation mechanism is surface warming and mixing. Regardless, web cams show fog quickly dissipating in the last hour or so. That will leave us with a quite nice spring day. Elongated high pressure aligned from the GA/SC coast to off the New England coast will promote a very light pressure and wind pattern. By the early afternoon, hi-res models show a well defined sea breeze developing and producing 10-15 mph of southerly to southeasterly flow. Clear skies will prevail this morning, followed by increasing high level cloudiness late in the day ahead of a shortwave crossing the lower Mississippi Valley. Temperatures are forecast to top out in the mid to upper 70s, which would be 3-5 degrees above normal for late March. Tonight: The weak sfc ridge of high pressure will continue to linger across the forecast area. At H5, near term guidance indicates that a shortwave will ripple SW to NE across Georgia and the Carolinas late tonight. Forecast soundings indicate that high clouds will gradually thicken as the shortwave approaches the forecast area. The developing partly cloudy conditions along with weak LLVL return flow should support milder low temperatures, lows ranging in the low to mid 50s. && .SHORT TERM /SATURDAY THROUGH MONDAY/... Moderate confidence this period. High pressure ridging into the area from the northeast into early Sunday will keep it dry despite an upper disturbance moving through Saturday. A cold front will approach from the west Sunday and shift offshore later in the day bringing some showers and possibly a few thunderstorms Sunday, with some showers continuing into Sunday night especially near the coast. Instability and forcing appear minimal Sunday so we think the threat for severe storms is very low at this time. Cooler high pressure will then begin to wedge into the area from the north Sunday night as some upper-level energy helps a surface low pressure system develop along the stalling cold front across the northern Gulf of Mexico and/or off the Southeast U.S. coast. This low should pass close to the area, likely just offshore, Monday night and Tuesday, and this is when the best rain chances are expected. Temperatures will be above normal through Sunday before falling well below normal Monday when some locales might not get out of the 50s, especially in SC where the low-level high pressure wedge will be strongest. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Low confidence through Tuesday and then moderate confidence thereafter. Inland high pressure wedging into the area from the north will likely persist as low pressure moves north near and just off the coast Monday night and Tuesday, although the timing and exact track of the low remain uncertain at this point. Some showers are possible Monday, especially southern and eastern portions of the forecast area. The best rain chances though will likely come Monday night into Tuesday during the closest approach of the low. Below normal temperatures should persist through mid week before returning to near normal Thursday and above normal Friday. Some inland spots could dip into the 30s Wednesday morning, with at least some patchy frost not completely out of the question in the normally colder locales. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... The main forecast challenge through 18z Saturday will be the potential for another round of fog Saturday morning. The overall setup is quite similar to Friday morning, though there is a bit more wind in the lowest few thousand feet of the column. Also, high clouds will be on the increase. Still think there will be at least some patchy fog around but not as significant as Friday morning. At KCHS, went with a period of ground fog with no restrictions. At KSAV, went with a few hours of MVFR fog. There is potential for fog to be locally dense again, but chances are lower than they were for Friday morning. Extended Aviation Outlook: Restrictions possible late Sunday and Sunday night then are more likely Monday into Tuesday as a cold front and then low pressure system affect the area. && .MARINE... Today and tonight: Ridging high pressure will linger over the marine zones through the period. Steady NE winds should range between 5-10 kt today and could become calm late tonight. A Small Craft Advisory will remain for the outer GA waters until 8 PM to highlight waves as high as 6 ft. Otherwise, wave heights across the near shore waters will range between 2-3 ft today and tonight. The outer Georgia waters should range between 4-5 ft tonight. Saturday through Wednesday: High pressure into early Sunday will keep conditions relatively benign. However, conditions will deteriorate later Sunday and especially Sunday night through Tuesday due to inland high pressure and coastal low pressure moving north across the waters. Small Craft Advisories will be needed during that time frame with some gale force gusts not out of the question as the low passes by, especially in the offshore waters. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...Small Craft Advisory until 8 PM EDT this evening for AMZ374. && $$ NEAR TERM...BSH/NED SHORT TERM...RJB LONG TERM...RJB AVIATION...BSH/RJB MARINE...NED/RJB