textproduct: Charleston

WHAT HAS CHANGED

All sections updated.

KEY MESSAGES

- 1) Locally dense fog possible Thursday morning.

- 2) Below normal rain chances through Saturday followed by increasing rain chances through Labor Day.

- 3) Hot and humid conditions expected into the upcoming weekend.

DISCUSSION

KEY MESSAGE 1: Locally dense fog possible Thursday morning.

Another round of fog/stratus appears likely again early Thursday morning as conditions remain similar to the last couple days. The 12Z suite of guidance points to single digit condensation pressure deficit values as well as probabilities for visibility <0.5mi as high as 60% according to the 12Z HREF. The best chances for dense fog appear to be west of Highway 17.

KEY MESSAGE 2: Below normal rain chances through Saturday followed by increasing rain chances through Labor Day.

Today: Strong high pressure in the mid-levels will lead to plenty of dry air aloft over the local forecast area. SPC mesoanalysis shows PWATs only around 1.8-1.9 inches. While a few short-lived showers are possible, most of the forecast area will remain dry this afternoon.

Thursday through Saturday: The forecast becomes more uncertain into the end of the week. The mid-level ridging will likely dominate over the southeastern states, but just to the south a plume of moisture associated with a mid-level disturbance could approach southeastern GA. Both the ECMWF and the GEFS show some degree of precipitation on Friday across SE GA. However, if the ridging holds stronger or the mid-level disturbance stays further south locations would remain dry. Saturday will likely be dry as the mid-level ridging builds over the southeastern states.

Saturday Night into Labor Day: A cold front will approach the area from the north Saturday night and move south into northern Florida on Sunday as a strong cyclone takes shape offshore of New England. Unsettled conditions look increasingly likely through Labor Day with breezy conditions possible at the coast as a wedge of high pressure builds across the Carolinas into Georgia. Drier conditions could return by Tuesday.

KEY MESSAGE 3: Hot and humid conditions expected into the upcoming weekend.

Aloft, a ridge of high pressure will extend from the Midwest to the Mid-Atlantic/Southeast regions, with the local area under its eastern periphery for the remainder of today and Thursday. High temps should top out in the low-mid 90s this afternoon with heat index values in the upper 90s to lower 100s, and the local area should experience similar results on Thursday as well while weak h5 vort energy and coastal troughing eventually shift onshore prior to the start of the weekend. Heading into the weekend, a notable increase in ridging occurs aloft. High temps should peak in the lower 90s Friday while sfc dewpts surge into the mid-upper 70s. Conditions appear to fall just short of Heat Advisory criteria to start off the weekend, but slightly warmer sfc temps (mid 90s) and higher dewpts (upper 70s) could lead to Heat Advisory conditions along the coastal corridor Saturday, before a cold front arrives early next week.

AVIATION /18Z WEDNESDAY THROUGH MONDAY/

Prevailing VFR through this evening at KCHS/KJZI/KSAV. There is a threat of fog developing early Thursday morning, possibly bringing some restrictions to the terminals. Guidance has the highest fog probabilities across far interior counties, inland from the terminals. However, fog is possible at all terminals, especially KCHS/KSAV. The 18Z TAFs feature slightly reduced visibilities and BR starting at 8/9Z. As confidence in fog location grows with future TAF issuances these details will adjust. Once fog dissipates Thursday morning VFR will prevail again.

Extended Aviation Outlook: Showers/thunderstorms could bring brief flight restrictions to the SAV terminal Thursday. Greater chances for flight restrictions with showers/thunderstorms arrive to all terminals this weekend prior to and during a passing cold front.

MARINE

Through Tonight: Southeast winds will remain less than 10 kt overnight with seas 2-4 ft, mainly in east/southeast swell with 11-13 sec periods.

Thursday through Monday: High pressure north/offshore and weak coastal troughing becoming positioned closer the Southeast Coast will support marine conditions well below Small Craft Advisory levels into late week, although scattered thunderstorms should return across a good portion of local waters by the start of the weekend. In general, onshore flow should peak between 10-15 kt daily through Saturday with greatest enhancement along coastal areas during afternoon sea breeze circulations. Seas should range between 2-4 ft. A cold front should then arrive Saturday night into Sunday, resulting in a slight uptick of winds (15-20 kt) and building seas (3-4 ft) into early next week. Should trends continue, there is a risk for Small Craft Advisories being needed post fropa early next week.

Rip Currents: There is a Moderate Risk for rip currents along the Southeast Georgia coast this afternoon and Thursday with modest onshore flow and 2-3 ft swells every 9-11 seconds. Should long period swell linger longer than expected, a Moderate Risk for rip currents could continue early weekend along the Georgia coast.

CHS WATCHES/WARNINGS/ADVISORIES

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