702 FXUS62 KCHS 172118 AFDCHS Area Forecast Discussion National Weather Service Charleston SC 418 PM EST Tue Dec 17 2019 .SYNOPSIS... A cold front will move well offshore overnight, followed by high pressure prevailing into late week. Low pressure should develop near the coast this weekend, before high pressure returns early next week. && .NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/... Rain has overspread most of the forecast area except near the central SC coast as of mid afternoon and will continue to push northeast ahead of a cold front moving through western SC/central GA. The strongest convection has been on the leading edge of this rain band with any severe threat quickly diminishing, mostly just confined to near the GA coast for the next hour or two. The initial weak cold front looks to push offshore this evening with winds turning west followed by another stronger front with colder and drier air from the north late. Low temperatures around daybreak should mostly range from the upper 30s well inland to mid 40s near the coast. Lake Winds: A Lake Wind Advisory has been issued for Lake Moultrie as winds are expected to gust near 25 kt overnight behind the cold front. && .SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/... Wednesday through Friday: Dry high pressure will prevail across the forecast area through the end of the week. Model time heights show a very dry column through this period, and the forecast is dry. The main story will be much cooler air that will encompass the area. Forecast highs for Wednesday and Thursday are in the low 50s for most areas, with a modest warm up into the mid and upper 50s expected by Friday. Overnight lows will feature low 30s and even some upper 20s well inland each night away from the immediate coast. By late Friday, a coastal trough is expected to develop just off the coast, and we could see isolated to scattered showers over the adjacent coastal waters as well as along the far southern portion of the Georgia coast. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Forecast confidence is somewhat low during the weekend with fairly large model spreads in regards to low pressure developing off the Southeast Coast. Latest trends suggest a more southern track of a mid/upper lvl low, which would keep most precip south of the region near sfc low pressure passing off the Southeast Coast. Given the trend, the potential for precip has been capped to chances across the area this weekend, but coverage should increase Friday night through Sunday as increasing low-lvl moisture and isentropic lift initially occur ahead of the mid/upper lvl trough shifting offshore and potentially enhancing the coastal trough near the Southeast South Carolina and Southeast Georgia coasts. Dry high pressure should then build across the region Monday into Tuesday with noticeably warmer conditions occurring under a building mid/upper lvl ridge aloft. In general, high temps should approach the mid 60s Monday, then mid/upper 60s Tuesday. Overnight lows should range in the low/mid 40s away from the coast to upper 40s/around 50 at the coast early next week. && .AVIATION /21Z TUESDAY THROUGH SUNDAY/... KCHS/KSAV: Moderate confidence this period through 06Z until a cold front passes through, then high confidence of VFR thereafter. Generally MVFR, possibly IFR or worse, late afternoon into early evening as showers and possibly a few storms push through. The best chance of thunder will be at KSAV. After the frontal passage, VFR should return by 06Z with winds gusting to near 20 kt from the NW and then N by daybreak. Extended Aviation Outlook: VFR conditions will prevail at both CHS and SAV terminals Wednesday into Friday. Low chances for flight restrictions are possible Saturday with showers that develop near a coastal trough along the Southeast Coast. && .MARINE... Tonight: Winds will increase behind an initial cold front this evening followed by a stronger surge late. Small Craft Advisories have been issued for all waters as winds gust 25-30 kt and seas build up to 4-5 ft within the nearshore waters and up to 6 ft across the offshore waters. Wednesday through Sunday: As high pressure builds in north of the area through Thursday, winds will steadily turn more northeasterly with time. The pressure gradient will be enhanced across the coastal waters, supporting elevated wind speeds through much the period. Ongoing Small Craft Advisories will end across the nearshore waters late Wednesday morning, while the advisory for the outer Georgia waters continues through the weekend. A surge of northeast flow is expected on Thursday behind a passing dry cold front, and we would see advisory conditions return for a short period of time. An area of low pressure is expected to develop across the northeast Gulf of Mexico this weekend, which will at least maintain the enhanced northeast pressure gradient across the waters. This could result in additional advisories for the local waters over the weekend. && .CHS WATCHES/WARNINGS/ADVISORIES... GA...None. SC...Lake Wind Advisory from 10 PM this evening to 7 AM EST Wednesday for SCZ045. MARINE...Dense Fog Advisory until 7 PM EST this evening for AMZ350-352- 354. Small Craft Advisory from 10 PM this evening to noon EST Wednesday for AMZ350-352-354. Small Craft Advisory from 7 PM this evening to 7 PM EST Sunday for AMZ374. Small Craft Advisory from 10 PM this evening to 7 AM EST Wednesday for AMZ330. && $$ NEAR TERM...RJB SHORT TERM...BSH LONG TERM...DPB AVIATION...BSH/RJB MARINE...BSH/RJB