Area Forecast Discussion
Issued by NWS Charleston, SC

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000 FXUS62 KCHS 070331 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1031 PM EST Fri Dec 6 2019 .SYNOPSIS... A weak disturbance will move through today. High pressure will build from the northwest tonight through Sunday. A warm front will lift north of the region Monday, before a cold front sweeps through the area late Tuesday. Strong high pressure will then return Wednesday through Friday. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/.. As of 1025 PM: An isolated thunderstorm was tracking east about 50 nm off the Charleston County, over AMZ370. Returns across Berkeley County were steadily decreasing. I will update the forecast to adjust PoP and sky trends over the next several hours. Temperatures are forecast to only cool by another 3-4 degrees before sunrise. As of 850 PM: KCLX detected light returns across the I-26 corridor of the SC Lowcountry. Sfc observations indicate that the returns were not associated with rainfall. However, I would not be surprised to hear of a few sprinkles in the area. I will maintain SCHC PoPs over the next couple of hours, then will drop the mention of showers through the rest of the night. As of 7 PM: KCLX detected several patches of light returns across SE GA. Observation stations under the returns did not observe rainfall at the sfc. I assume that the returns were associated with wet mid-level clouds. I will update the forecast to adjust sky and temperatures through this evening. Previous Discussion: This Evening: A mid-level short wave will move overhead while deamplifying. Closer to the surface, lift associated with this feature combined with a plume of PWATs stretching from the ocean towards the Charleston Tri-County area will lead to scattered showers in the evening. Models are in good agreement showing the "heaviest" precipitation early, with both intensity and areal coverage decreasing as the evening progresses. QPF should generally be <0.01". Tonight: The mid-level wave will quickly shift offshore. At the surface, a weak cold front will approach from the north. Though, models have it weakening/dissipating as it crosses through our area. What may end up being more noticeably is surface high pressure building behind the front late tonight. Clouds should generally decrease, especially late. Temperatures may be somewhat tricky, depending partly on the cloud cover. Lows should generally be in the 40s. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/... Dry high pressure will expand across the area from the northwest on Saturday. The upper shortwave will be far enough east initially to keep any inverted trough development well off the coast. Therefore we do not anticipate any precipitation Saturday. A secondary shortwave will move into the Southeast Saturday night and Sunday. The surface ridge will shift farther to the east, pushing an inverted trough closer to the coast before it lifts north Sunday night and Monday. A few rain showers could skirt through northern areas Sunday night and Monday though most areas will remain dry. A warm front will lift north on Monday. Temps in the 60s Saturday and Sunday will warm well into the 70s on Monday as a southerly flow develops. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... The mid and upper trough will amplify to our west early next week, allowing for a cold front to approach from the west late Tuesday, which will likely pass through Tuesday night. There remain enough timing differences between the global models to not show anything higher than chance PoP ahead of the front, but higher chances will be required at we draw closer to the event. Any t-storm risk is too low to include this far in advance. Confidence is excellent that it`ll be unseasonably warm, with H85 temps as great as 12-13C Tuesday. Behind the cold front a large and robust high pressure system with dry and colder weather will dominate the local vicinity Wednesday and Thursday, before it gives way to another upstream cold front late in the week. An extended period of breezy to windy conditions will prevail through the period with large pressure rises and a tight gradient around the high. && .AVIATION /04Z SATURDAY THROUGH WEDNESDAY/... Prior to the 0Z TAFs, KCLX detected several patches of light returns across SE GA. Observation stations under the returns did not observe rainfall at the sfc. I assume that the returns were associated with wet mid-level clouds. High pressure centered over the mid-Atlantic states will build south across the forecast area late tonight through Saturday. Dry low levels will support a VFR forecast. Winds will remain light to calm tonight, then winds will become steady from the NE after sunrise Saturday and remain through the day. Extended Aviation Outlook: Overnight stratus will be possible Sunday night through Wednesday night, possibly resulting in flight restrictions. && .MARINE... Tonight: Initially, their won`t be much of a pressure gradient across the waters, which will lead to light and variable winds. However, later tonight, high pressure building in from the north should increase the pressure gradient, causing winds to turn to the north and increase to around 10 kt. Seas initially 1-2 ft could build a foot by daybreak Saturday. A pinched northeast gradient on Saturday will result in the onset of Small Craft Advisory conditions for all Atlantic waters outside Charleston Harbor. We have SCA headlines beginning at varying times Saturday or Saturday night. Conditions will improve late Sunday across the nearshore waters due to a warm front lifting through and southerly flow returning. SCA conditions will persist over the offshore GA waters through much of next week due to a combination of winds/seas. Sea Fog: Conditions still point to at least a chance of sea fog on Monday as temps and dew points climb greater than the underlying waters. Should this occur the most likely time frame would be Monday within a favorable S-SW fetch and before winds increase too much. Confidence is not yet supportive of adding mention to the forecast, nor to the Hazardous Weather Outlook. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...Small Craft Advisory from 6 PM Saturday to 5 PM EST Sunday for AMZ352-354. Small Craft Advisory from 8 AM Saturday to 6 AM EST Thursday for AMZ374. Small Craft Advisory from 8 AM Saturday to 5 PM EST Sunday for AMZ350. && $$ NEAR TERM...NED SHORT TERM...JRL LONG TERM... AVIATION...NED MARINE...JRL is the U.S. government's official web portal to all federal, state and local government web resources and services.