textproduct: Charleston

WHAT HAS CHANGED

All sections updated.

KEY MESSAGES

- 1) Patchy fog possible tonight into early Wednesday morning, mainly across locations west of I-95.

- 2) Scattered showers and perhaps a thunderstorm or two will be possible Thursday and Friday as a front approaches and moves through the region.

DISCUSSION

KEY MESSAGE 1: Patchy fog possible tonight into early Wednesday morning, mainly across locations west of I-95.

High pressure will maintain its hold over the local forecast area through tonight and into Wednesday morning. Dew points this afternoon are generally in the upper 60s to around 70 across the region. Cross over temperatures will likely be able to be reached overnight tonight across inland locations as low temperatures drop into the low 60s. The 12Z REFS shows probabilities of <0.5 mi visibilities in the 30-40% range west of I-95. A Dense Fog Advisory may be required for portions of the forecast area.

KEY MESSAGE 2: Scattered showers and perhaps a thunderstorm or two will be possible Thursday and Friday as a front approaches and moves through the region.

Aloft, ridging in place on Wednesday will get pushed off the coast as an upper low moves into the Great Lakes region. A trough will then shift through the Upper Midwest and mid MS Valley into Friday, pushing a front towards the forecast area. For Thursday, model consensus is that the bulk of the forcing and low level convergence will remain displaced inland, likely keeping most of the forecast area dry. So any showers and thunderstorms will be mainly a concern for the interior of the forecast area and likely even moreso still further inland than that. It will be quite warm, with low to mid 80s, and this could result in enough surface-based instability to produce a few thunderstorms. Still, we anticipate most of the area (if not all) to remain dry).

For Friday, the forecast area will be in an area of cyclonic flow aloft on the far southern periphery of an upper low across the Great Lakes. The best shortwave energy rotating around the upper low will pass by to the north and northwest of the forecast area. The surface front should start getting into the area in the morning, pushing offshore into the evening and early morning hours. The front should bring a broken band of mostly scattered coverage of showers with a thunderstorm or two possible.

Overall, the lack of notable forcing and coverage will keep the rainfall potential on the low end. In fact, most probabilistic guidance keeps the chances of 0.25" or more of rainfall at less than 20% for most of the forecast area. Also, while a few thunderstorms will be possible, the strong/severe risk is very low.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

VFR to start the 18Z TAF period at KCHS/KJZI with some brief moments of MVFR expected at KSAV this afternoon. Fog is forecast to develop across the region tonight, however confidence in impacts at the terminals is low as the fog could remain inland. At this juncture have BR mentioned in all TAFs with 5SM at KCHS/KJZI and 3SM at KSAV. Any fog/ground fog should clear by mid-morning with prevailing VFR there after.

Extended Aviation Outlook: Isolated to scattered showers, and possibly a thunderstorm or two, could impact the area Thursday and Friday. Any resulting flight restrictions are expected to be brief.

MARINE

Rest of Today through Tonight: Surface high pressure will continue to dominate over the marine waters, yielding NE winds between 15 to 20 knots. Seas will generally be 3 to 5 ft across the nearshore waters, with 4 to 6 ft in the 20 to 60 nm offshore GA waters where a Small Craft Advisory remains in place through Wednesday morning.

Wednesday through Sunday: Conditions across the local water will continue to improve Wednesday as the gradient relaxes and allow for onshore easterly flow no more than 10-15 knots. Light southeasterly to southerly flow is expected Thursday before turning southwesterly ahead of an approaching front. The front will pass to the east Friday night, though there a significant surge is not expected in its wake. Seas will steadily improve as well. Seas up to around 5 feet will continue in the outer GA waters on Wednesday, with 2-4 feet expected for the most part across all waters through the weekend.

CHS WATCHES/WARNINGS/ADVISORIES

GA...None. SC...None. MARINE...Small Craft Advisory until 7 AM EST Wednesday for AMZ384.