966 FXUS62 KCHS 030818 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 418 AM EDT Mon Jun 3 2019 .SYNOPSIS... A cold front will move into the area today and push south tonight. High pressure will then build into the region from the north, before shifting offshore mid week. A weak inland surface trough will then prevail late week with an increasing potential for unsettled weather this weekend into early next week. && .NEAR TERM /THROUGH TONIGHT/... Today: The forecast area will remain within a persistent west- northwest flow regime aloft. At the surface, a front will sink into the area this morning and then remain in the vicinity of the coast into the evening. It's hard to call this a cold front since temperatures today will still rise well into the 90s. Instead, as it sits along the coast this afternoon it could provide just enough low level convergence, especially with the development of the sea breeze, to kick off a few weak showers and thunderstorms. Hi-res model solutions show isolated convection right along the coast this afternoon and this seems reasonable given the presence of the front. Any activity that develops should be weak though, given the weak thermal profiles in model soundings. Have added a narrow zone of 20 percent rain chances for a few hours this afternoon. Model thickness values support highs in the mid 90s across the board, with a few upper 90s possible in southeast Georgia. Tonight: If any convection does develop in the afternoon along the coast, it will dissipate quickly in the evening. High pressure will build into the central Appalachians, pushing whatever is left of the front south of the forecast area. As prevailing easterly low level flow arrives late tonight, a few models are trying to produce some light shower activity along the South Carolina coastal zones. Current thinking is that this is overdone and we have maintained a dry forecast. Lows are forecast to fall into the mid 60s inland, ranging to the low to mid 70s along the coast. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... Tuesday: Surface high pressure over the Mid Atlantic region early in the day is forecast to move off the coast during the afternoon. Our synoptic pattern will feature low level synoptic flow off the Atlantic which will result in a much more progressive sea breeze and temps running at least 5-8 degrees less in the coastal corridor during the afternoon hours. Models continue to show an inverted surface trough developing inland with slightly deeper moisture and some mid level instability. Isolated to locally scattered showers and tstms are expected mainly along/west of U.S. 17 and especially adjacent to the CSRA and far southern SC Midlands. Tuesday night, there are hints at a weak short wave in northwest flow aloft and while there could be some nocturnal convection, models are not in agreement are we maintained a dry forecast for the overnight. Wednesday and Thursday: The pattern will favor a typical setup leading toward early summertime with a broad mid level ridge and deeper layered moisture. Pwats should build toward 2.0 inch by Thursday with mainly diurnal chances for scattered afternoon and evening convection. High temps will warm a couple degrees from Wednesday into Thursday with highest chance POPs over inland zones each afternoon/evening. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... The axis of the mid level ridge is forecast to move offshore by Friday while a surface trough extends from central GA across the Carolina Piedmont region. Deep moisture and broad low level convergence will result in scattered coverage of convection on Friday. We continue to trend toward an unsettled weekend into next Monday as a broad upper trough and deep moisture result in bouts of convection across the region. Since global models lack agreement on the strength of the upper trough and timing of embedded waves, we capped rain chances at 50 percent during daytime periods. Temps are expected to be near or slightly above climo during the period. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... VFR conditions are expected to prevail at KCHS and KSAV through 06z Tuesday. There is a very low end chance for an isolated shower or thunderstorm near the terminals late this afternoon. The chance of direct impacts is too low to explicitly include in the forecast at this point. Extended Aviation Outlook: Mainly VFR. Brief restrictions will be possible mid to late week in late night/early morning low clouds. At least isolated, mainly diurnal convection is possible mid to late week. && .MARINE... Today through Tonight: A weak front will move to along the coast today and then push south of the area tonight as high pressure builds in from the north. Westerly flow will prevail early becoming southerly this afternoon. Winds along the land/sea interface this afternoon should top out around 15 knots. Then late tonight, east to northeast winds will start to take hold, first across the Charleston County waters. Winds will increase late, and could be as high as 15-20 knots for portions of the local waters by late tonight. Seas are expected to average around 2 feet for most of the period, becoming 2-3 feet late tonight. High pressure will move offshore to the northeast of the local waters Tuesday. Models continue to show a decent pressure gradient which is expected to become enhanced along the land/sea interface once the sea breeze pushes inland late Tuesday morning. We bumped wind speeds up a tad and now show 15-20 kt more solid across near shore waters and seas 3-5 ft, highest beyond 20 NM off GA's coast. Mid to late week will feature a bit lighter winds with a typical south to southwest synoptic flow around the offshore ridge. Seas will range 2-3 ft on average. && .FIRE WEATHER... Another hot and dry afternoon is expected today. Relative humidity values are expected to fall into the 25-30 percent range, lowest along and west of the I-95 corridor. There is some potential for values to even fall into the 20-25 percent range across interior southeast Georgia. Winds are expected to be less gusty than on Sunday, and therefore it was determined a Fire Danger Statement was not needed. && .TIDES/COASTAL FLOODING... The evening high tide will occur around 9 pm and is expected to rise into the 7.0 to 7.3 ft range in Charleston Harbor. The astronomical high tide is 6.35 ft, so we would need to see a tidal departure of around 0.7 ft to reach shallow coastal flooding thresholds. Fort Pulaski will rise to near 9.2 ft, but could fall just short. A Coastal Flood Advisory will likely be needed for at least a portion of the coast. Shallow coastal flooding will be possible with the evening high tide cycle through at least mid week, especially along the SC coast. && .EQUIPMENT... WFO Charleston SC will only conduct upper-air soundings at 12Z until further notice due to a shortage of helium. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...BSH SHORT TERM... LONG TERM... AVIATION...BSH MARINE...BSH FIRE WEATHER... TIDES/COASTAL FLOODING... EQUIPMENT...