Area Forecast Discussion
Issued by NWS Charleston, SC
Issued by NWS Charleston, SC
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195 FXUS62 KCHS 300744 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 344 AM EDT Mon Sep 30 2024 .SYNOPSIS... A broad area of Low pressure will persist over the region through Tuesday. A dry cold front is forecasted to move through the region later Wednesday, followed by cooler High pressure through the rest of the work week. An area of Low pressure may pass south of the region next weekend. && .NEAR TERM /THROUGH TONIGHT/... Today: Aloft, the forecast area will continue to sit in the area between the large ridge to the southeast that stretches from the eastern Gulf of Mexico and into the central Atlantic, and the upper low near the central Appalachians. Through the day, the upper low will start to make some eastward progress and the flow pattern across the forecast area will increasingly take on an anticyclonic curvature. At the surface, a weak area of low pressure will slip into the central Carolinas with an associated surface trough that will extend back into central Georgia. This setup will continue to produce southwesterly flow in the low- level across much of the region. The airmass will be characterized by precipitable water values in the 1.25-1.50" range, with model soundings depicting plenty of mid-level dry air and warm temperatures. Such an environment will not be particularly supportive of the development of showers, which is supported by hi-res model output. Instead, shower development seems more likely inland across the Midlands closer to the aforementioned surface trough. The last day of September will bring another warm day with above normal temperatures. Look for highs in the upper 80s across the entire area. Tonight: No change to the overall setup and quiet conditions. There are no significant concerns for fog and lows are forecast to range from the mid to upper 60s inland to the low 70s along the coastal corridor. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... Tuesday: The mid-levels will consist of a positively tilted shortwave over the Southeast and Lower MS Valley in the morning. It`ll slowly shift eastward during the day, with it`s axis becoming located off the coast late at night. At the surface, a broad area of Low pressure will be over or just north of our region during the day, then shifting offshore overnight. Additionally, a dry cold front will be approaching from the west and northwest late at night. Though, it`s not expected to reach our area during this time period. Just about all of the synoptic models and long-range CAMs keep our area dry, with POPs peaking around 10% along the immediate coast during the afternoon. Despite mostly cloudy skies, thickness values support temperatures well above normal. Highs will be in the mid to upper 80s. Lows will range from the mid 60s far inland to around 70 degrees at the immediate coast. Wednesday: A positively tilted mid-level trough will be located off the Southeast U.S. in the morning. As it slowly moves further offshore during the day and into the night, weak ridging will gradually build over the Southeast. A dry cold front will be located to our west and northwest in the morning. It`s forecasted to move through our area during the late afternoon or evening, then shift further offshore after midnight. High pressure located to our north northwest will then build in overnight. Given the lack of moisture, POPs peak at no more than 10% during the afternoon and with the frontal passage. Expect some cumulus in the afternoon and evening, followed by clearing skies after midnight. Some compression ahead of the front will yield temperatures a few degrees above normal. Highs will be in the mid to upper 80s. Lows behind the front will range from the mid 60s far inland to around 70 degrees at the beaches. Thursday: The mid-levels will consist of weak ridging over the Southeast U.S. and the Mid-Atlantic States. At the surface, a cold front will stretch off the Southeast U.S., and to our south in the morning. Meanwhile, High pressure will be centered over the Mid-Atlantic States. The cold front is forecasted to move further away from us, pushed by the High that should shift off the Mid-Atlantic Coast later in the day. Subsidence associated with the High will keep our area rain-free. However, when the High shifts offshore this will cause moisture and clouds to start increasing from south to north during the late afternoon. High temperatures should be in the low to mid 80s. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... High pressure passing to our distant northeast will bring our area dry conditions Thursday night. What happens Friday into the weekend may hinge on the potential placement, timing, and strength of a disturbance over the western Caribbean Sea. NHC has highlighted this region in the Tropical Weather Outlook, so refer to this product for the latest information. Likewise, NHC and WPC collaborated the WPC Surface Fronts and Sea-Level Pressure maps during this time period. They have Low pressure tracking northward across the eastern Gulf of Mexico on Friday, then northeastward on Saturday, and then nearing the western FL coast by Sunday morning. As for us, our long term forecast is the NBM. && .AVIATION /08Z MONDAY THROUGH FRIDAY/... VFR conditions are expected to prevail at KCHS, KJZI, and KSAV through 06z Tuesday. There is a very small chance that an isolated shower could impact KCHS or KJZI through about 10z. Otherwise, quiet conditions are expected. Extended Aviation Outlook: Mainly VFR. Periods of ground fog could cause brief flight restrictions around dawn through Friday. && .MARINE... Today through tonight: Southwest flow will turn a bit more due southerly this afternoon and early this evening with the sea breeze, before turning more westerly late tonight. Wind speeds will generally top out in the 10-15 knot range. Seas will average 2 ft, but could be up to 3 ft at times beyond 20 nm. A broad area of Low pressure will be over or just north of our waters Tuesday, then shifting offshore Tuesday night. A dry cold front will approach from our west and northwest Wednesday morning. It`s forecasted to move through our waters Wednesday evening, then shift further offshore after midnight. High pressure located to our north northwest will then build in Wednesday night, passing to our north on Thursday, then moving off the Mid-Atlantic Coast Thursday night. An area of Low pressure may pass south of our region next weekend. Despite all of these synoptic features, winds and seas are expected to remain below Small Craft Advisory criteria through the end of the work week. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM...BSH SHORT TERM... LONG TERM... AVIATION...BSH MARINE...BSH