Area Forecast Discussion
Issued by NWS Charleston, SC

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000 FXUS62 KCHS 260507 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1207 AM EST Sun Jan 26 2020 .SYNOPSIS... High pressure will prevail through Sunday. A mid and upper level disturbance will impact the area late Sunday night into early Monday. High pressure will be the main feature through the middle of the week. A storm system could impact the region late next week. && .NEAR TERM /UNTIL 6 AM THIS MORNING/... No major changes were made for the midnight update. Did nudge sky cover up into the mostly cloudy category as the cirrus overhead is pretty thick. && .SHORT TERM /6 AM THIS MORNING THROUGH TUESDAY/... Sunday: A broad and somewhat cyclonic flow will prevail aloft, as surface high pressure initially across Alabama and Georgia is nudged a little southeast into Florida throughout the day. This occurs in response to a short wave dropping through the Central Plains, while another short wave moving into the northwest Gulf of Mexico triggers cyclogenesis at the surface to the south of Louisiana. We`ll experience an increase in mid and high level clouds during the afternoon as a 140-150 kt upper jet traverses the area. Dependent on how quickly this transition occurs and how opaque these clouds get with determine our max temps. We currently went a tad below the low level thickness forecast and a blend of the MOS guidance to produce max temps near or a bit above climo, with a dry but offshore synoptic flow. Sunday night into Monday: Surface high pressure will hold generally across and/or near Florida, while low pressure meanders in the central Gulf of Mexico. Of more importance is a fast moving short wave that arrives overhead from the west late Sunday night and exits into the ocean Monday morning. The associated QG forcing and PWat that reaches 0.75-0.85 inches will produce at least 50-70% PoP between about 3 am and 9 am Monday. Since the short wave is such a quick feature, QPF will be on the light side, with currently no more than around 0.1-0.2 inches to occur. The temp curve Sunday night will be rather atypical, not only warmer than tonight will be, but temps will generally hold steady or even climb as thicker clouds move in overnight. Cloudy skies early Monday will give way to slow clearing, and the resulting max temps look to be similar to Sunday. Tuesday: The flow aloft will be quasi-zonal, as one short wave passes to the north, a second passes through the Florida keys, and a third and more significant short wave drops through Texas. Meanwhile, surface high pressure will build in locally from the northwest, as strengthening low pressure passes near Dallas and Houston, Texas. With plenty of sunshine, temps will warm about 20F from the morning, reaching the upper 50s and lower 60s. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... High pressure and dry conditions are expected Tuesday night. A quick moving storm system could bring some showers to our area late Wednesday and Wednesday night, followed by dry conditions on Thursday. Models indicate another, possibly stronger storm system developing to our west on Friday, then approaching. The exact location and strength of this system will determine the potential impacts to our area. For now, we went with chance POPs with the expectations that they may need to be raised significantly with future forecasts. && .AVIATION /05Z SUNDAY THROUGH THURSDAY/... VFR. Extended Aviation Outlook: A quick moving storm system could bring periodic flight restrictions late Sunday night into Monday morning. Otherwise, VFR should prevail. && .MARINE... The Small Craft Advisory for the Georgia offshore leg has been cancelled. Seas at 41004 have are right around 5 ft and the latest WW3 output suggests seas have finally dropped below 6 ft in the far eastern portions of the Georgia offshore zone. Overnight: Offshore flow will prevail between high pressure to the west and low pressure to the north. Could see some gusts near 20 kt at times well offshore. Seas will average 2-3 ft nearshore and 4-5 ft offshore. Sunday: High pressure covers the eastern Gulf of Mexico and parts of the Southeast, with a modest W-NW flow in the morning that slackens a little in the afternoon. We still have a Small Craft Advisory in effect for AMZ374 where some 6 footers will be common out near 50-60 nm off the coast through 10 am. No headlines elsewhere. Sunday night through Tuesday: A mid and upper level disturbance will move through the area late Sunday night into Monday morning, before high pressure becomes the main feature into Tuesday. Winds and seas will stay beneath any advisory levels. Only showers are expected with the short wave aloft. Wednesday through Thursday: High pressure covers much of the eastern part of the nation, while low pressure looks to stay to our south. As a result, winds and seas are again less than any advisory thresholds. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...None. && $$

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