textproduct: Charleston

SYNOPSIS

A frontal system will maintain unsettled weather through early next week, then cold high pressure will build in. A reinforcing cold front will move through late next week.

NEAR TERM /UNTIL 6 AM SUNDAY MORNING/

Tonight: The mid-levels will consist of WSW flow overhead. The upper- level jet streak located to our northeast will move away. At the surface, a frontal boundary will remain situated well to our south and southeast. High pressure will be located well to our north. Models have the rainfall ending from north to south this evening as drier air begins to nudge into the region from the west. Though, isolated to scattered showers should persist over McIntosh County and its vicinity for much of the night. Most areas should receive little QPF accumulation tonight, except McIntosh County and its vicinity, which should get less than 0.25". The combination of some stratus build down this evening, abundant low-lvl moisture (including wet grounds), and light/calm winds should lead to some fog formation, mainly after midnight. However, ongoing trends suggests thick high clouds this evening and guidance indicating an increase in 1000mb geostrophic winds late night could limit the window for areas or widespread fog to become dense overnight. Conditions will continue to be monitored for any potential Special Weather Statement or Dense Fog Advisory overnight. Otherwise, low temperatures will range from the upper 30s far inland, to the mid to upper 40s along the immediate coast.

SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/

A broad upper-lvl trough with reinforcing shortwaves will continue to dominate the forecast pattern. At the surface, a front shall reside over portions of northern Florida and extend into the Atlantic adjacent to the South Carolina coastline. This pattern will yield north-northwesterly flow with PWAT values ranging between 0.8 to 1.0". Also, this will allow deep-layer onshore flow to enhance low-lvl moisture across the southeast on Sunday. Expect light to moderate scattered showers Sunday afternoon with the greatest chance across southeast Georgia. Recent QPF guidance indicates less than 0.10 inches with localized higher amounts (0.25 to 0.50 inches) across southeast Georgia where showers could train and/or linger. Model soundings indicate a saturated profile below ~750-800 mb with a shallow isothermal layer, indicating a possible persistent of low stratus throughout Sunday. With limited mid-lvl lapse rates and no appreciable CAPE, convection remains negligible. Onshore flow and cloud cover will mitigate strong radiational heating and highs will likely only reach into the mid to upper 50s. As the upper-lvl trough gradually shears eastward, another shortwave will pass over the region on Sunday night. This will yield light scattered showers overnight through Monday morning. These showers will likely taper off by the early afternoon on Monday with rainfall totals less than 0.10 inches. Expect a dry, cold front to push across the region on Monday evening/night, and then high pressure to build into the region behind it. This will result in quiet weather on Tuesday with skies gradually clearing throughout the day. Temperatures will remain slightly below average with highs in the low to mid 50s (with some spots of upper 50s in Southeast Georgia). It could become quite cold on Monday and Tuesday night with temperatures dropping down into the upper 20s inland and then low to mid 30s closer to the coastline.

LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/

As mid-lvl ridge shifts eastward into the Southeast, strong subsidence will promote a quiet and rain-free forecast on Wednesday and Thursday. Also, increasing WAA will support a noticeable warm-up mid-week as temperatures reach into the mid to upper 60s. However, this pattern only lasts momentarily, as a reinforcing cold front sweeps across the region on Friday. Expect increasing cloud cover and strengthening southwesterly flow aloft to develop ahead of the approaching front. There's moderate uncertainty pertaining to this weekend as ensemble spread remains large. Cooler temperatures will likely return this weekend following the passage of the front.

AVIATION /00Z SUNDAY THROUGH THURSDAY/

Periods of MVFR/IFR are likely at CHS/JZI/SAV terminals this evening and tonight, along with light rains producing MVFR vsbys at times through about 03Z Sunday. There could be a brief period of VFR conditions at the terminals prior to midnight, but most guidance suggests IFR cigs to develop and hold at the terminals until during the second half of the night. Slow improvement, but prolonged MVFR cigs are possible at CHS/JZI from 13Z Sunday to 00Z Monday. IFR cigs should hold at the SAV throughout the day Sunday with additional rain/showers occurring during the afternoon and possibly occurring through 00Z Monday.

Extended Aviation Outlook: A relatively prolonged period of MVFR with occasional IFR ceilings expected through early next week. This system will likely produce low ceilings and reduced vsbys. Expect improving coniditons late Monday night.

MARINE

Tonight: A frontal boundary located well to the south and southeast of the coastal waters will support WNW winds in the 10-15 kt range this evening (slightly weaker across Georgia waters), veering to the NE by daybreak Sunday. Seas should average 2-3 feet. Showers and low clouds could produce some visibility reductions at times.

Sunday through Wednesday: A prolonged period of north- northwesterly flow, driven by a series of shortwaves passing across the local waters, will dominate through mid-week. Expect wind speeds to remain rather light with 5 to 10 kts on Sunday, and then increase to 15 to 20 kts with gusts near 25 kts on Monday as the aforementioned cold front approaches. Thereafter, winds will taper back and remain light on Tuesday and Wednesday. Seas will range 2 to 3 ft on Sunday, and then build modestly to 3 to 5 ft with some 6 footers tapping into the the nearshore Charleston and outer Georgia waters on Monday evening into Tuesday. Therefore, Small Craft Advisories will likely be needed on Monday evening into Tuesday. Afterwards, the swell looks to ease back as high pressure returns to the Atlantic waters on Wednesday and conditions rapidly improve.

TIDES/COASTAL FLOODING

Astronomical tides will remain elevated Sunday but will be on a declining trend. Coastal Flood Advisories could be needed for the Sunday morning high tide cycle, but the current forecast is for Charleston to fall just shy of the minor coastal flood threshold.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...None.