Area Forecast Discussion
Issued by NWS Charleston, SC

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000 FXUS62 KCHS 180551 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 151 AM EDT Wed Sep 18 2019 .SYNOPSIS... A cold front will advance through the area early today. High pressure will then build south into the region later today and continue into early next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... As of 150 AM: I will issue a quick update to align PoP and Wx with recent radar trends. Generally keeping SCHC to CHC PoPs along and south of the Savannah River. Otherwise, the current forecast appears in good shape. Previous Discussion: Quick Update to add slight chance POPs to Allendale County and surrounding areas. Radar shows isolated thunderstorms approaching this area. The HRRR indicates they should persist for at least the next 2-3 hours. We may need to expand this areal coverage further, depending on the future radar trends. Otherwise, a cold front will move south and should make it toward the Altamaha River near daybreak as Hurricane Humberto well offshore continues to move farther away. Some showers are expected to develop as moisture, instability and convergence increase a bit. Can`t rule out some weak storms but any thunder should mainly be confined to around the GA coast where the greatest instability is expected. Temperatures should fall to around 70 north and west toward the Pee Dee/Midlands with lower to mid 70s south and east toward the coast and GA Coastal Empire. && .SHORT TERM /6 AM THIS MORNING THROUGH FRIDAY/... Wednesday: Models in good agreement that the backdoor front will move through the area from north to south during the day. Models show some increase in moisture associated with the front and this is supported by cloud cover across Virginia at the present time. Some minor instability is expected to develop mainly in the afternoon across southeast Georgia. Threat for precipitation is low enough in the north due to the early arrival of the front that it was left out of the forecast. Highest rain chances will be in the south. Threat for precipitation will end by late afternoon. Made some minor adjustment to lower high temperatures from the Allendale/Walterboro areas south to near Savannah. Maintained highs in the mid to upper 80s southwest of this area, but have some concern that cloud cover may be sufficient enough to keep the high temperatures from getting that high. Highs will mainly be in the lower 80s in the north and along southeast South Carolina Coast. Drier air will move in behind the front with lows Wednesday night ranging from near 60 in the north to near 70 along the southeast Georgia Coast. Thursday: Drier air will continue to overspread the area in the wake of the cold front. The only exception will be along the southeast Georgia Coast near the Altamaha River where a few very light marine showers could brush the coast. Brisk northeast winds are expected along the coast. High temperatures area wide will be rather mild and this combined dew point temperatures in the 50s inland to the lower to mid 60s at the coast will make for a rather pleasant day. Highs should range from the upper 70s near the South Santee River to the mid 80s across far inland portions of southeast Georgia. A few light marine showers are possible in southeast Georgia mainly east of I-95 Thursday night. Friday: As surface high pressure begins to build from the Mid- Atlantic states into the western Atlantic, surface winds will become more onshore especially from Beaufort County south and this will allow the threat for some light marine showers to spread further inland especially across southeast Georgia. Highs should range from near 80 along the coast to the mid 80s far inland where more sunshine is expected and there is basically no threat for precipitation. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Deep layered ridging will persist over the weekend and then tend to break down during the first part of next week. Models continue to show dry weather prevailing through the entire period. High temps are expected to warm slightly above climo during the period, however overnight temps should continue to fall into the 60s each night away from the ocean as the atmosphere remains quite dry. && .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/... A backdoor cold front will slide south across KCHS early this morning and KSAV during the early daylight hours. The approach and passage of the cold front may support a few showers near KSAV this morning, I will highlight with VCSH at KSAV. High pressure is expected to build across the terminals through the afternoon. The combination of mixing and a weak pressure gradient should support gusts near 20 kts at KCHS this afternoon. Clearing sky and decreasing winds are expected across the terminals this evening. Extended Aviation Outlook: VFR conditions will prevail. && .MARINE... Tonight: A cold front will move south through most, if not all, of the waters with winds picking up from the northeast behind it. Seas will also build as a result and Small Craft Advisories are in effect for all waters except Charleston Harbor and the nearshore GA waters. Wednesday through Sunday: Northeast winds will dominate throughout the week in the wake of the backdoor cold front that moves through the waters on Wednesday. The combination of increasing seas and winds will result in Small Craft Advisory conditions for all coastal waters into Friday evening for the nearshore waters and well into Saturday night for the offshore Georgia waters. Looks like the best threat for Small craft Advisory conditions to occur in Charleston Harbor will be on Thursday. Later shifts will need to further evaluate and if necessary issue an advisory there. Rip Currents: Moderate Risk through Wednesday due to lingering elevated long period swells and increasing longshore currents due to strengthening northeast winds. The rip current risk will remain elevated through the end of the week as northeast winds and strong longshore currents continue. && .TIDES/COASTAL FLOODING... Low chances for minor coastal flooding around the times of high tide through late week, especially along the South Carolina coast. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...Small Craft Advisory until 8 PM EDT Friday for AMZ352. Small Craft Advisory until 4 AM EDT Sunday for AMZ374. Small Craft Advisory until 8 PM EDT Friday for AMZ350. Small Craft Advisory from 11 AM this morning to 8 PM EDT Friday for AMZ354. && $$ NEAR TERM...NED SHORT TERM...MTE LONG TERM... AVIATION...NED MARINE...MTE/RJB TIDES/COASTAL FLOODING...

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