Area Forecast Discussion
Issued by NWS Charleston, SC

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000 FXUS62 KCHS 181603 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 1103 AM EST Sat Jan 18 2020 .SYNOPSIS... A warm front will lift through the region later today and this evening. A cold front is expected to move through late tonight into Sunday, followed by cold and dry high pressure into the middle of next week. A low pressure system could impact the region next weekend. && .NEAR TERM /THROUGH TONIGHT/... A weak high pressure wedge will persist across the Charleston Tri-County area through mid-afternoon. Elsewhere, winds will more quickly veer to southerly with increasing warm air advection. A fairly wide temperature range is anticipated from north to south today. The combination of stratus and cold advection over northern areas is expected to keep temps from rising much higher than the low 60s, while farther south where sunshine and warm advection develop, temps may approach 70. Can`t rule out a few showers over the waters and immediate coastal areas though the forcing associated with the weakening coastal trough is quite limited. Tonight: An ill-defined warm front will lift north of the area early this evening and surface flow is forecast to veer to SW ahead of an approaching cold front. Warming temps along coastal zones should set the stage for increasing SW winds in the 10-15 mph range this evening. If warm temps become realized, there could be some gusts over 20 mph tonight. Ahead of the front, deeper moisture profiles appear to shift through S GA with upper forcing rather unfocused through the overnight. We generally maintained good chance POPs, rainfall amounts should be less than a tenth of an inch. Temps will rise ahead of the front with readings in the lower 60s overnight at many areas. && .SHORT TERM /SUNDAY THROUGH TUESDAY/... Sunday: A cold front will progress through the area during morning hours, favoring scattered showers across much of the area (highest coverage along the Southeast Georgia coast). Cool and dry high pressure will then build in wake of the front, quickly ending precip from northwest to southeast during early afternoon hours and resulting in a downward trend of temps during mid-afternoon hours through the evening. In general, highs should range in the low/mid 60s ahead of fropa early. Conditions will remain dry through the overnight period while colder air arrives from the west-northwest. In general, temps should cool into the low 30s inland to mid/upper 30s closer to the coast. Monday and Tuesday: Dry and cold high pressure will prevail at the sfc below a broad trough of low pressure expanding across the East Conus. The pattern will result in noticeably colder conditions on Monday with temps some 10-15 degrees lower than the previous day. In general, high temps will struggle to reach the upper 40s across northern areas and lower 50s across Southeast Georgia. Temps will be chilly Monday night, dipping into the upper 20s away from the coast to low/mid 30s along the beaches. Tuesday afternoon temps should be even colder as the center of a mid-lvl low shifts across the Southeast while northeast sfc winds prevail at the sfc. Highs should only reach the mid 40s across Southeast South Carolina and upper 40s across Southeast Georgia. && .LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... A large area of sfc high pressure will dominate much of the East Conus with its center shifting across the Midwest midweek, then into the Northeast by Friday. Aloft, a large trough of low pressure will begin to shift offshore midweek, setting up a period of mid-lvl ridging through late week. The pattern will favor cold temps Tuesday night with lows in the mid/upper 20s away from the coast, before conditions gradually warm as winds become more directly onshore through late week. Temps will likely warm into the low/mid 50s Wednesday, then mid 50s well inland to upper 50s/lower 60s on Thursday. On Friday, onshore winds should prevail as high pressure shifts off the East Coast. A developing coastal trough could also bring some showers onshore. In general, temps should approach the mid/upper 60s. Chances of precip should increase during the weekend as low pressure over the Gulf of Mexico merges with a cold front approaching from the west on Saturday. Scattered to potentially numerous showers are possible during peak forcing/moisture across the area Saturday afternoon. && .AVIATION /16Z SATURDAY THROUGH WEDNESDAY/... MVFR cigs are possible around the SC corridor from mid morning through mid afternoon as a coastal trough nudges near shore. At KSAV, the chances for lower cigs should be a bit lower, but still possible. This evening, VFR conditions at both terminals likely per latest forecast soundings and time/height cross sections. Later tonight, scattered showers are expected ahead of a cold front. The timing looks late enough to allow the next TAF cycles to include shower potential as well as cig flight restrictions. Extended Aviation Outlook: Flight restrictions are possible at both CHS and SAV Sunday morning during showers associated with a passing cold front. VFR conditions are then expected at both terminals Sunday afternoon through the middle of next week. && .MARINE... Marine conditions should gradually improve today as the gradient becomes weaker. Winds may be slow to veer initially, directions will become S to SW by this evening. We may need to issue another SCA for Charleston nearshore later tonight as seas build offshore with stronger flow expected out near the Gulf Stream. Since it will be marginal, will allow for 12Z model run data before any SCA re-issue considerations. A cold front will approach from the west late but suspect winds will be gustier right along the land/sea interface than over the coldest shelf waters. Sunday through Thursday: A cold front will shift across coastal waters Sunday, turning southwest winds to west-northwest in its wake. A Small Craft Advisory will be ongoing across offshore Georgia waters through much of the day and could be needed across northern South Carolina waters off the Charleston County Coast due to lingering 6 ft seas. Conditions should be somewhat elevated heading into Monday as the pressure gradient remains enhanced and northerly winds rush in colder air across the waters. Strongest cold air advection should occur Monday night through Wednesday when a mid-lvl low shifts across the region. Small Craft Advisories are likely for at least a portion of the coastal waters during this period and could linger into Thursday, especially across offshore Georgia waters where northeast winds support the continuation of higher seas. In general, north-northeast wind speeds should range between 25-30 kts at times Tuesday and Wednesday while seas build to 4-6 ft across nearshore waters and 6-9 ft across offshore waters. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...None. MARINE...Small Craft Advisory until 6 PM EST Sunday for AMZ374. && $$ NEAR TERM...JRL SHORT TERM...DPB LONG TERM...DPB AVIATION... MARINE... is the U.S. government's official web portal to all federal, state and local government web resources and services.