000 FXUS62 KCHS 200523 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 123 AM EDT Tue Apr 20 2021 .SYNOPSIS... Weak high pressure will remain over the region early this week. Then, a cold front will sweep across the region on Wednesday. High pressure will then return for late week. Low pressure will impact the area over the weekend. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... The center of dry high pressure will push over the region tonight, with scattered to maybe broken mid and high level clouds arriving after midnight, especially south and west. This is in association with the upper jet that passes over the local area. Since the air mass is so dry, winds will be light or calm away from the coast, and we're already several degrees cooler than 24 hours ago, we look for min temperatures a bit cooler than last night. The cloud cover that moves in will slow the decline of temperatures, but we still look to fall to the lower and middle 50s most places inland from US-17, with upper 50s and lower 60s along the barrier islands, in downtown Charleston and near Lake Moultrie. && .SHORT TERM /6 AM THIS MORNING THROUGH THURSDAY/... As high pressure moves away from the area and into the Atlantic on Tuesday, low pressure will move off the coast of Florida in an eastward direction across the Atlantic. While there will be increased isentropic lift and PWATs will be around an inch, any shower activity will likely remain just along the coast and across the coastal waters. Most inland areas should remain rain-free. High temperatures will be in the 70s. Thereafter, a surface low will make its way across the Ohio River Valley overnight Tuesday. Low temperatures will be in the mid to upper 50s inland and low 60s just along the coast. Then on Wednesday, a dry cold front associated with the low will then move through the area and as the pressure gradient tightens, winds will become gusty. Though, the day should be mostly sunny with high temperatures in the upper 70s to low 80s. Lows will be in low to upper 40s inland with low 50s just along the coast due to cold air advection. For Thursday, high pressure will generally prevail and it will be a nice, sunny day. High temperatures will be in the mid 60s to low 70s inland and low 60s just along the coast. Lake Winds: Winds ahead and behind a cold front will become quite gusty due to a tightening pressure gradient. A Lake Wind Advisory could be needed for Lake Moultrie. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... Overnight Thursday, high pressure will prevail and low temperatures will be in the mid 40s to low 50s inland and mid 50s just along the coast. Then on Friday, another dry day and mostly sunny skies is expected. Though, as a deep-layered trough moves closer to the area from the west, cloud cover will slightly increase. High temperatures will be in the 70s with lows in the mid to upper 50s inland and low to mid 60s just along the coast. While there is still uncertainty within the models for timing and location of the approaching low pressure, rain chances will increase on Saturday into Sunday morning. The best chance of rain looks to be during Saturday afternoon into the overnight. By daybreak, the low pressure should be comfortably to the northeast and the cold front should be offshore. Though, a secondary cold front could then move through the region. The majority of Sunday and all of Monday should be rain-free as high pressure quickly builds into the area. High temperatures will be in the mid to upper 70s to low 80s each day. Low temperatures will be in the 50s inland and low 60s just along the coast. && .AVIATION /06Z TUESDAY THROUGH SATURDAY/... VFR through 06Z Wednesday. SE winds will become a little gusty in wake of the sea breeze this afternoon. Extended Aviation Outlook: Mainly VFR. Gusty winds likely on Wednesday, then again on Saturday. Flight restrictions will also be possible on Saturday due to showers/thunderstorms. && .MARINE... High pressure will build over the region tonight. As pressures rise from the NE, a bit of wind surge will push from the NE to SW across the coastal waters tonight. N and NW winds will veer around to the ENE, and strengthen to 10 to 15 kts with gusts to 20 kts after midnight over the marine zones outside the CHS Harbor. Seas will increase slightly from 1-2 ft early on, to around 2 ft across most areas by daybreak. Tranquil marine conditions expected to last through early Wednesday. Then, ahead of an approaching cold front, winds will increase by Wednesday afternoon to 15-20 knots and Small Craft Advisories could be needed for winds and seas through Thursday morning. High pressure will then build into the area and tranquil marine conditions should return through late Friday. Another round of Small Craft Advisories could be needed over the weekend due to another approaching cold front. && .FIRE WEATHER... A combination of gusty winds, low relative humidity, and dry fuels could produce hazardous fire conditions Wednesday afternoon/early evening. Near critical relative humidity values will persist Thursday and Friday afternoons, although winds will remain less than 15 mph. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM... SHORT TERM...RAD LONG TERM...JRL/RAD AVIATION... MARINE... FIRE WEATHER...