Area Forecast Discussion
Issued by NWS Charleston, SC

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000 FXUS62 KCHS 221415 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1015 AM EDT Thu Mar 22 2018 .SYNOPSIS... High pressure will prevail through Saturday. A cold front will drop through the area on Sunday as high pressure wedges in from the north. High pressure will then persist through the middle of next week. && .NEAR TERM /THROUGH TONIGHT/... Today: Upper troughing will persist over the region while cool high pressure remains to the west. No precipitation expected given the dry air mass in place, as evidence by the 0.36 inch PWAT from the 12Z CHS sounding. Low-level cold advection is forecast to diminish slowly and winds will be downsloping from the west northwest but after a chilly start it will be slow to warm. Highs should only top out around 60 across the Lowcountry and lower to mid 60s farther south, generally warmest in GA south of I-16 in GA. It will not be as windy compared to yesterday but some gusts near 20 mph are expected at times. Tonight: The main concern will be the potential for freezing temperatures and frost. Based on what happened this morning regarding temperatures where some observations hit freezing we have issued a Freeze Watch for areas mainly north and west of Charleston, Walterboro, Hampton and Sylvania. Even if freezing temperatures do not occur frost will be likely for most areas away from the coast and thus at the very least Frost Advisories will likely be issued later today even if Freeze Warnings are not. && .SHORT TERM /FRIDAY THROUGH SUNDAY/... High pressure will drift over the eastern U.S. on Friday and then into the Atlantic on Saturday. Concurrently, an area of low pressure will move east across the Ohio River Valley on Saturday, which will place a developing warm front to our north. Quiet weather is expected as best forcing and moisture remains out of the area. Below normal temperatures on Friday will moderate on Saturday as the forecast area becomes increasingly positioned in the warm sector ahead of the approaching low. A cold front will quickly drop south through the forecast area on Sunday as high pressure wedges in from the north. Passing shortwave energy will help provide lift for showers along the front. Models continue to show varying coverage in precipitation, with the GFS indicating some heavier rainfall than the ECMWF and Canadian as the front gets into our GA zones. Have maintained current PoP scheme which peaks around 40%. Should have a decent temperature gradient across the area as highs in far southeast Georgia peak in the mid 70s ahead of the front, while the north remains in the low 60s. && .LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/... Models are in good agreement through the long term period. A wedge of high pressure will persist over the area on Monday, resulting in cloudy and cool conditions with possibly some lingering light rain. The wedge will then weaken on Tuesday as the high expands over the region. Quiet weather and warming temperatures expected the remainder of the period as strong mid level ridging takes hold. && .AVIATION /14Z THURSDAY THROUGH MONDAY/... VFR at KCHS/KSAV through 12Z Friday. Extended Aviation Outlook: VFR through Saturday. Sub-VFR ceilings possible early Sunday through Monday as a front drops into the area. && .MARINE... Improving conditions are expected today as low level cold air advection ebbs while high pressure builds east over the coastal waters. By this afternoon, offshore flow will be below 20 kt well offshore and 15 kt near shore. Speeds will remain elevated over GA waters from Grays Reef seaward with occasional gusts to 25 kt possible in AMZ374 overnight. Elsewhere, conditions well below SCA thresholds in near shore waters with seas less than 3 ft. Friday through Tuesday: Rather benign marine conditions expected Friday into early Saturday as high pressure transitions into the Atlantic. South/southwest winds will then increase on Saturday as a low pressure system approaches from the west. Some gusts near 25 knots will be possible in the outer Georgia waters, but at this time think a small craft advisory will not be needed. Winds and seas will really deteriorate on Sunday behind a cold front that will drop south through the waters. Advisories will be likely beginning Sunday afternoon and will continue through Monday as a wedge of high pressure settles in. Conditions are expected to improve Tuesday as the high expands over the area and the pressure gradient relaxes. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...Freeze Watch from late tonight through Friday morning for GAZ088. SC...Freeze Watch from late tonight through Friday morning for SCZ040-042>045-050-052. MARINE...None. && $$ NEAR TERM...RJB SHORT TERM...ECT LONG TERM...ECT AVIATION... MARINE... is the U.S. government's official web portal to all federal, state and local government web resources and services.