textproduct: Charleston
This forecast discussion was created in the public domain by the National Weather Service. It can be found in its original form here.
SYNOPSIS
High pressure prevail across the area through the middle of the week. A cold front could approach by the end of the week.
NEAR TERM /UNTIL 6 AM MONDAY MORNING/
A wedge of high pressure will remain anchored over the Southeast U.S. tonight as a subtle coastal trough lingers just offshore. Guidance is similar in showing a slight tightening of the pressure gradient near the coastal trough overnight resulting in an increase in convergence at the coast. The greatest convergence looks to setup from roughly Edisto Beach south to Saint Catherines Sound and this is where the greatest coverage of showers is expected through sunrise. Pops were nudged up to into the 30-40% range in this corridor and may need to be ramped up further with the late evening update depending on the latest radar and short term model trends.
Breezy conditions will persist at the beaches with winds 15-25 mph with gusts 30-35 mph, or just shy of Wind Advisory levels. Lows tonight will range from the upper 50s well inland to the mid- upper 60s at the beaches with a few mid 50s possible in the Francis Marion National Forest and areas north of Lake Moultrie.
SHORT TERM /6 AM MONDAY MORNING THROUGH WEDNESDAY/
The forecast for the early to middle part of the week will largely be driven by the surface high moving east of New England and into the north Atlantic, allowing for more onshore flow along the SC/GA coast. This will produce improving moisture profiles and the passage of subtle low-level convergence near the presence of a coastal trough. This setup should yield higher rain chances, though still mainly in the form of isolated to scattered showers. Model guidance is in good agreement with the feed of showers favoring the Georgia coast and pushing inland into southeast Georgia. Later in the day, an additional round of showers will be possible that could impact the entire coast and southeast South Carolina. Perhaps less shower activity on Tuesday before we move into Wednesday. The forecast get a bit more complex for Wednesday as we start to see the details hinge on the location and strength of a possible tropical system in the southeast Gulf of Mexico. For now, global models feature the best rain chances across southeast Georgia with a significant decrease the further north and northeast you go, suggesting less rain potential for southeast South Carolina. Temperature still look to be above normal through the period, with highs in the upper 70s and low 80s.
LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/
The long term period begins Wednesday night and Thursday with solid model agreement concerning the potential for a much needed widespread rainfall event. The combination of a surface trough, deep moisture around a possible tropical system in the Gulf of Mexico, and supportive upper jet dynamics are enough to introduce some likely (~60%) rain chances into the forecast. Thereafter, high pressure is expected to return and bring either dry conditions or very low rain chances through the weekend.
AVIATION /00Z MONDAY THROUGH FRIDAY/
04/00z TAF Discussion: KCHS/KJZI/KSAV: VFR conditions will give way to possible MVFR conditions overnight, especially at KSAV. Prevailing MVFR cigs were highlighted at KSAV 08-14z with a TEMPO for MVFR cigs 05-08z to account for an expected lowering trend. Farther north at KCHS and KJZI, confidence in MVFR conditions is not as high, but TEMPO groups were introduced 06-09z to account for possible MVFR cigs noted in some guidance. Shower activity will increase over the Atlantic and move onshore overnight. Activity looks to focus south of KCHS and KJZI, although it could be close at KJZI. KSAV will likely be impacted late tonight through just after sunrise. Activity looks to remain fairly light so no major reductions in vsbys are expected at this time. There is a chance shower activity may linger beyond 14z at KSAV, so some adjustments may be needed for the 06z TAF cycle.
Extended Aviation Outlook: Mainly VFR. Periods of MVFR conditions will be possible with passing showers into the middle of the week.
MARINE
Tonight: A stationary front to the south will dissipate this evening, followed by surface troughing developing offshore overnight. Meanwhile, high pressure will shift off the New England coast overnight. This will cause the surface pressure gradient to remain enhanced, leading to gusty NE winds. Though, winds should gradually ease and veer overnight. Small Craft Advisories are in effect for all of the marine zones tonight. Though, the advisory for Charleston Harbor is more borderline.
Monday through Friday: Persistent northeasterly to easterly winds will remain elevated in the 15-20 knot range for much of the upcoming week. The main result will be elevated seas of 6 ft or higher from around 10 nm and out through the middle of the week. Small Craft Advisories remain in effect for all waters (excluding Charleston Harbor), primarily for seas. We have extended the nearshore waters through Wednesday night, and the outer Georgia waters continue through the end of the week.
High Surf: Model guidance suggests that 8 ft seas could be present within the nearshore waters Monday night into Tuesday. This could produce breakers as high as 5 ft in the surface zone at local beaches. If this occurs, a High Surf Advisory could be needed.
TIDES/COASTAL FLOODING
Strong northeast winds will cause tidal anomalies to increase the next few days. Minor coastal flooding is possible with the Monday morning high tide for Charleston County and Coastal Colleton.
CHS WATCHES/WARNINGS/ADVISORIES
GA...None. SC...None. MARINE...Small Craft Advisory until 6 AM EST Monday for AMZ330. Small Craft Advisory until 6 AM EST Thursday for AMZ350-352- 354. Small Craft Advisory until midnight EST Friday night for AMZ374.
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