385 FXUS62 KCHS 100852 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 452 AM EDT Sun Mar 10 2019 .SYNOPSIS... A cold front is expected to shift over the region tonight into early Monday. High pressure will then prevail through late week before another cold front shifts through the region during the weekend. && .NEAR TERM /THROUGH TONIGHT/... Pre-dawn: Southwest flow in the boundary layer has been increasing overnight ahead of a cold front. Dry weather has prevailed and while high clouds have been moving offshore, warm air advection stratocu fields continue to increase. Mild temps have been on the rise since midnight, in the lower/middle 60s just about everywhere. Today: A cold front will struggle to cross the mountains as the surface boundary tends to parallel the mid level flow while strong surface heating is expected ahead of the front across much of our forecast area in the warm sector. During almost all of the day, models indicate a region of persistent NVA at 500 MB will linger and this suggests convective rains should hold off until late day over inland zones and we have backed off on POPs a bit given latest model trends. While a few showers or isolated tstms are possible out ahead of pre-frontal convective rains, the lack of any upper forcing suggest the coastal corridor could end with dry weather for most all of the afternoon hours. It looks to be well above climo with temps warming into the lower to mid 80s many areas inland from the immediate coast. Late in the day, a few stronger tstms may develop across parts of Eastern Central GA into the CSRA under a pocket of somewhat better mid level instability and ahead of a weak mid level short wave. Inspection of soundings in this region show very dry air anchored above 700 MB and even weak CIN values around 850 MB limiting the initial air mass. It even appears that before any deeper convection reaches our inland areas, it should be late in the day with diminishing ML/SB CAPES to work with. While deep layered shear is > 30 kt, it looks like the risk for isolated strong tstms will be limited to our zones well inland adjacent to the CSRA/Southern Midlands and only for a brief period around 00Z/11. Tonight: Scattered pre-frontal convective rains will gradually spread east over the region as Pwats surge over 1.6 inches ahead of the cold front. Marginal instability remains for a tstms but we maintained slight chance thunder in the evening zones for all but some far southeast GA zones. A few spots west of I-95 could see tenth to a quarter inch rains, however the general trend will be amounts diminishing to lighter amounts after midnight as we lose more instability aloft and less favorable low level convergence. Ahead of the front, temps will remain mild overnight, in the 60s for much of the area. There is also a chance for some coastal stratus/fog developing and advecting onshore a short distance this evening. If sea fog does indeed develop, it could be a brief issues for some of the beaches of upper GA and southern SC. && .SHORT TERM /MONDAY THROUGH WEDNESDAY/... A cold front will slowly depart the area Monday morning, producing only a few showers over southern most areas of Southeast Georgia along/south of the front. Dry and eventually cooler conditions will then move into the area as high pressure builds over the region from the northwest and prevails through midweek. Temps should remain fairly warm on Monday while the center of sfc high pressure enters the Midwest. In general highs should range in the mid/upper 70s, warmest in southern areas. Monday night lows will be cooler than the previous night, dipping into the low/mid 50s. On Tuesday, dry/cool high pressure will become more dominant as winds turn northeast in response to the center of high pressure tracking east over the Midwest. Highs will struggle to warm into the upper 60s/lower 70s Tuesday afternoon despite a full sun. Tuesday night lows will be noticeably cooler than the previous night, dipping into the mid/upper 40s inland to low/mid 50s near the coast. By Wednesday, the center of high pressure will likely approach the Mid-Atlantic Coast while mid/upper lvl ridging occur over the Southeast United States. Given the pattern, another dry day is expected, but temps should be a few degrees warmer, peaking in the low/mid 70s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... A large mid/upper lvl ridge of high pressure will extend over the Southeast United States during the second half of the week while a large mid-upper lvl trough of low pressure shifts over the Central United States. At the sfc, high pressure centered along the Mid- Atlantic Coast will shift over the western Atlantic, setting up southerly winds over the area well ahead of a cold front approaching the region this weekend. The pattern will likely result in a noticeable warmup late week with temps that approach the mid/upper 70s Thursday, then upper 70s/lower 80s Friday before chances of showers and/or thunderstorms develop in advance of the cold front Friday afternoon/evening. Chances of precip appear greatest Friday night into early Saturday as PWATs approach 1.5 inches along/near cold fropa. The front should then push well offshore by Saturday afternoon with cool/dry high pressure returning to the area late weekend into early next week. Once fropa occurs, temps will struggle to warm into the mid/upper 60s Saturday and Sunday afternoon. && .AVIATION /08Z SUNDAY THROUGH THURSDAY/... VFR at KCHS and KSAV at least most of the time through 06Z Monday. The only exceptions might be for a period of flight restrictions due to stratus and/or fog late tonight into mid morning. We continue to hold off on mentions in the 06Z TAF set as confidence remains low. Any showers and possible t-storms with the next cold front will stay inland from the terminals through at least 00Z Monday but during the 03Z-06Z time frame convective rain risk does appear to increase. We introduced VCSH in the last 6 hours. Extended Aviation Outlook: VFR conditions are expected at both CHS and SAV terminals through Thursday. && .MARINE... A south to southwest flow over the waters ahead of the cold front through tonight. Poor near-surface lapse rates and shallow stable marine layers will keep wind speeds mainly below 15 kt over shelf waters. Seas will be 2-4 ft, highest beyond the pilot buoys. Monday through Friday: A cold front will shift offshore early Monday, temporarily enhancing the pressure gradient over coastal waters and helping produce wind gusts up to 15-20 kt at times as a northeast sfc flow prevails Monday night into Tuesday. Seas should also build up to 3-5 ft. Conditions should then slowly improve over the coastal waters mid-late week as high pressure centered north/northwest of the area shifts off the Mid-Atlantic Coast and turns sfc winds more east/southeast Wednesday/Thursday, then more south by Friday. In general winds should be no higher than 10-15 kt mid to late week while seas range between 2-4 ft. Sea Fog: South/southwest winds will help advect deeper moisture over cooler shelf waters through tonight. At least patchy dense sea fog will be possible as air with dew point temperatures in the lower to mid 60s moves across water temperatures in the mid to upper 50s. Latest guidance suggest areas of dense fog are most likely to occur later today and this evening. Marine Dense Fog Advisories may be required. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM... SHORT TERM...DPB LONG TERM...DPB AVIATION...DPB MARINE...DPB