715 FXUS62 KCHS 110225 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1025 PM EDT Thu Apr 10 2025 .SYNOPSIS... A cold front will move through our area on Friday, bringing some showers. High pressure then returns for the weekend and the first part of next week, keeping conditions dry. A dry cold front should move through on Tuesday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... A broad trough will prevail aloft across the bulk of the eastern United States, with a strong embedded short wave to move into the area overnight. A cold pool of convection has already developed, and although they will be in a somewhat weakening trend as they draw closer, we have adjusted the forecast to show some higher PoPs than previous. Upstream convection is moving fairly steadily east-southeast, and utilizing the Distance Speed Tool in AWIPS, it shows the leading edge arriving in Allendale, Jenkins, and Screven County between 12 and 1 AM. This is mainly in line with the HRRR, and as such activity will make it near the I-95 corridor around 2-4 AM, and then off the coast by around 4 or 5 AM. Although CINH will be increasing as the convection moves in from the west and northwest, MLCAPE is progged to be around 500-750 J/kg, maybe even as great as near 1000 J/kg close to the South Carolina coast, and SCP values are as much as 1-2 units. While low level lapse aren`t that impressive, mid level lapse rates are favorable around 6.5-7.0C/km. This coincides with increasing upward omega and TTI near 50. There is a swath of higher DCAPE of 700-800 J/kg, but this looks to be well out ahead of the convection, so odds are against any severe weather. However, those DCAPE values should be enough to produce locally strong wind gusts of 30-40 mph. This is also shown by the HRRR, and to some degree the GFS LAMP guidance. We have attempted to show this in the grids, by blending that guidance with the pre- existing forecast. Probably can`t rule out a little small hail given the cold temps aloft (minus 16-17C at 500 mb). The best chance for any strong t-storms, based generally off the HRRR, is north of I-16 in Georgia. It`ll be a warmer night than the past couple of nights, with winds in most places never decoupling, and cloud cover to increse and thicken. Lows will generally drop to the mid and upper 50s, with maybe a few spots near the Atlantic right around 60F degrees. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/... Friday: The mid-levels will consist of a trough strengthening/amplifying along the East Coast. This will cause heights to lower overhead. Though, most of the trough`s energy should remain just to our north. At the surface, in the morning a trough will be located just offshore, while a cold front will be to our west. Ahead of the front, a plume of moisture will overspread our area. PWATs could peak ~1" in the morning. This value is a bit above normal for this time of year per the CHS sounding climatology. Though, it`s far from any extreme values. For this reason, along with a lack of lift, the deterministic models and the CAMs generally have isolated to scattered showers across most of our area in the morning. Most of these showers get pushed closer to the coast around noon and early in the afternoon, as drier air builds in from the west. Any isolated showers late in the afternoon should dissipate around sunset. QPF during the day should be 0.1" or less in most areas. We also must note that SPC continues to have our Charleston Tri- County and the rest of the immediate coast under a Marginal Risk of severe weather. MLCAPEs struggle to get to a few hundred J/kg and this is backed up by model soundings. Even a lot of the experimental data has very little, if any severe weather probabilities. Therefore, this risk continues to seem overdone, and it may be difficult for us to get any thunder. Otherwise, high temperatures should peak in the 70s. The late evening and overnight will be dry as High pressure builds in from the west. Skies will also become mostly clear, with northwest winds ushering cooler temperatures into our area. Lows should be in the 40s, except warmer at/near the beaches. Saturday and Sunday: A mid-level trough will be over the East Coast Saturday morning. It`ll slowly shift offshore by late Sunday. At the surface, broad High pressure initially over the central MS Valley Saturday morning will gradually approach, becoming located over the Southeast U.S. by late Sunday. The High will bring our area dry conditions. Saturday, northwest surface winds ushering cooler temperatures into our area will keep high temperatures in the upper 60s to maybe lower 70s. Saturday night, mostly clear skies and light winds will lead to decent radiational cooling. Lows should mostly be in the 40s, except 50s at/near the beaches. Sunday, high temperatures will rise into the lower to middle 70s, except cooler at the beaches. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... High pressure will bring our area dry conditions and temperatures rising to above normal on Monday. A dry cold front should move through on Tuesday. Dry conditions and relatively cooler temperatures are expected Wednesday and Thursday. We`ll have to monitor for potential fire weather concerns on Wednesday. && .AVIATION /02Z FRIDAY THROUGH TUESDAY/... KCHS/KJZI: VFR will prevail through the 00Z TAF cycle, although there will be a weakening band of convection that impacts the terminals overnight ahead of a cold front. We show VCTS as a result, and there could be a period from 07-10Z where brief flight restrictions and gusty winds (25-35 kt) occur with the convection. Most of Friday looks to be rainfree, but maybe some boundary interactions with upstream convection and the sea breeze could spur some activity in the late afternoon or evening. Deep mixing will yield gusty W winds after 15Z Friday, with peak winds near or even stronger than 20 kt. KSAV: VFR will prevail through the 00Z TAF cycle, since the better chance of convection stays north and west of the terminal overnight. But it could be close enough where we felt compelled to carry VCSH. Most of Friday looks to be rainfree, but maybe some boundary interactions with upstream convection and the sea breeze could spur some activity in the late afternoon or evening. Deep mixing will yield gusty W winds after 15Z Friday, with peak winds near or even stronger than 20 kt. Extended Aviation: Brief flight restrictions are expected Friday due to a cold front moving through our area. Afterwards, VFR will prevail. && .MARINE... Rest of tonight: Weak high pressure will give way to the approach of a cold front late. This will result in winds that start off SE and S, and are then forecast to steadily veer around to be SW late. Speeds will also increase late tonight, with sustained winds around 15 knots and a few gusts up to 20 knots possible. Seas are expected to average 3-4 feet across the nearshore waters and 4-5 feet in the outer waters. isolated to scattered t-storms are expected after 2 or 3 AM, which can generate strong winds and lightning strikes. Marine Weather Statements and/or Special Marine Warnings might be necessary if the convection holds together given MLCAPE near 1000 J/kg and DCAPE of 600-700 J/kg. Friday: Expect elevated SW winds in the morning and afternoon, as a cold front approaches our area. The front will quickly move through in the evening, then offshore overnight. Winds will veer to the NW behind the front and stay elevated. However, no Small Craft Advisories are expected. Weekend through Monday: High pressure should bring fairly tranquil weather conditions. Tuesday: A dry cold front should move through, bringing increased winds and seas. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$ NEAR TERM... SHORT TERM... LONG TERM... AVIATION... MARINE...