Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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392 FXUS62 KCHS 180609 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 209 AM EDT Wed Sep 18 2024 .SYNOPSIS... Low pressure across the Carolinas will weaken through mid week. High pressure will then develop inland late this week, and persist into the weekend. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... Broad circulation center remains nearly fixed over the western Carolinas early this morning with some semblance of a surface trough stretching through the central Carolinas into central Georgia along with some semblance of a boundary draped across northern Florida into the Atlantic. A few showers have developed in parts of far southeast Georgia/northeast Florida over the last several hours where there is some modest instability and low level convergence ongoing. Some remnant showers/sprinkles are working up through the far southern part of the forecast area. Rest of tonight: Quiet conditions overall although there will be some modest low-mid level moistening and the possibility for a few showers to spread into parts of southeast Georgia by morning. Temperatures will not move much from current readings with lows largely in the middle to upper 60s. && .SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/... Wednesday: The mid-levels will consist of a trough over the East Coast. Embedded within it will be a Low, roughly 579 dam at 500 mb. It`ll be located just to our northwest in the morning. But it`ll shift to the north and elongate, becoming located over the Mid- Atlantic States overnight. At the surface, a stationary front will be spread over our far inland zones, or just to our west during the day. It`ll start to transition to a cold front and move towards the coast by daybreak Thursday. There will be a decent amount of moisture in place with PWATs peaking around 2", which is around the 90th percentile for this time of year. Both the synoptic models and the long-range CAMs have isolated, light showers developing over by the late morning. By the afternoon, scattered showers are expected across most of our area. A few rumbles of thunder are also possible. The showers should gradually decrease as the atmosphere stabilizes in the evening, then things dry our over land overnight. High temperatures will be in the mid to maybe upper 80s, except cooler at the beaches. Low temperatures will be in the upper 60s, except lower 70s at the beaches. Thursday: A mid-level trough will be over the East Coast in the morning. Embedded within it will be a Low located over the Mid- Atlantic State. While the trough will stay in place, the Low will shift towards New England. The surface stationary front will be spread over our coast at daybreak. It`ll quickly shift offshore as time progresses. High pressure will then form further inland. PWATs will initially be as high as 2" in the morning. Though, they`ll gradually trend lower as time progresses. The combination of this moisture and lift from the front and maybe sea breeze will lead to isolated showers along our coast in the afternoon, and scattered shower across the Charleston Tri-County. A few rumbles of thunder are also possible. These showers will quickly dissipate during the evening, with it being dry overnight. High temperatures will again be in the mid to maybe upper 80s, except cooler at the beaches. Low temperatures will be in the mid/upper 60s, except lower 70s at the beaches. Friday: The mid-levels will consist of a trough over the East Coast, with an embedded Low over or near New England. At the surface, broad High pressure will be over roughly the mid- Appalachians. This will usher much drier air into our region, with lower PWATs and dew points. Expect a mostly sunny day with a bit of an increase in clouds during the afternoon. Northeast winds will keep highs in the low to mid 80s. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... WPC has High pressure over portions of the Southeast U.S. for much of the long term. The NBM reflects this thinking well. Simply put, we`ll have dry conditions with temperatures at or slightly below normal. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... Overall VFR conditions will prevail at KCHS, KJZI, and KSAV through 06z Thursday. There could be some shallow ground fog around sunrise, but no restrictions are expected. Isolated to scattered showers will also be possible around KSAV around or just after sunrise, and continuing through a good portion of the day. The potential for showers, and possibly a thunderstorm, will then shift to around KCHS and KJZI for the afternoon. However, confidence in timing and direct impacts is too low to include anything other than VCSH at this time. Extended Aviation Outlook: Very brief flight restrictions are possible due to showers again Thursday afternoon/evening. Otherwise, VFR. && .MARINE... Tonight: Southerly flow this evening will gradually turn more southwesterly with time overnight. Wind speeds should generally be 10 knots or less. Seas should average 2-4 feet. Low pressure and a stationary front across the Carolinas will weaken on Wednesday. The front should transition into a cold front and quickly move through the waters on Thursday. High pressure will then prevail inland Friday and persist into the weekend. Additionally, Low pressure should be located well to our northeast this weekend. Sustained winds will generally be 10 kt or less Wednesday with seas 2-4 ft. Wind direction will change as the front moves through on Thursday, while seas are 2-3 ft. Northeast winds become more dominant starting on Friday. They may be at their strongest each night. Regardless, both winds and seas appear to remain just below Small Craft Advisory criteria throughout the long term time period. Rip Currents: The combination of a lingering swell around 2 ft at 9 seconds and high astronomical tides from the full moon will lead to a Moderate Risk of rip currents for all of our beaches on Wednesday. && .TIDES/COASTAL FLOODING... Positive tidal anomalies along with high astronomical tides from the full moon will lead to elevated tides for the rest of this week. Coastal Flood Advisories will probably be needed, especially for Charleston and coastal Colleton Counties. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$