textproduct: Charleston

WHAT HAS CHANGED

Key Message 1 have been updated.

KEY MESSAGES

- 1) The risk for coastal flooding and coastal hazards continues.

- 2) Seasonable temperatures and generally dry conditions are expected through Thursday.

- 3) The National Hurricane Center (NHC) has identified Tropical Storm Isaias in the southwestern Gulf. Regardless of track across the Gulf, heavy rainfall could develop over the Southeast United States by this weekend.

DISCUSSION

KEY MESSAGE 1: The risk for coastal flooding and coastal hazards continues.

For Charleston and Coastal Colleton Counties, gusty/persistent northeast winds associated with a wedge of high pressure inland and low pressure offshore in combination with high astronomical tide levels will likely support additional coastal flooding issues during high tide cycles through Thursday, and possibly into Friday. The high tide during late afternoon/early evening hours later today will be the greatest concern when minor to potentially low-end moderate saltwater flooding is possible (~7.4 ft MLLW at the Charleston Harbor). Otherwise, minor coastal flooding is possible with remaining high tides.

For Beaufort, SC to McIntosh, GA Counties, the greatest risk for coastal flooding is expected with the late afternoon/early evening high tide cycle today (~9.5 ft MLLW at Fort Pulaski, GA). Coastal Flood Advisories could be issued later today for this area.

Rip Currents/High Surf/Beach Erosion: The setup remains highly favorable rip currents today with gusty northeast winds expected. A High Risk is highlighted for the Georgia beaches with a Moderate Risk for the South Carolina beaches today.

KEY MESSAGE 2: Seasonable temperatures and generally dry conditions are expected through Thursday.

As we remain between a surface high pressure to our north and a stationary front to our south, winds may become breezy later this morning and into the afternoon. Breeziest winds are expected along the coastline (near 30 mph in SE GA, to near 25 mph in SE SC) while areas inland may see gusts to 20 mph. Otherwise, despite partly to mostly cloudy skies, temperatures continue to moderate today into the upper 70s to lower 80s. Dry conditions are expected, though an isolated shower can't be ruled out near Darien, GA. Weak ridging builds on Thursday with dry northeasterly surface flow keeping the region dry, resulting in an overall rather pleasant mid-October day with highs in the upper 70s to lower 80s and light winds.

KEY MESSAGE 3: The National Hurricane Center (NHC) has identified Tropical Storm Isaias in the southwestern Gulf. Regardless of track across the Gulf, heavy rainfall could develop over the Southeast United States by this weekend.

Tropical Storm Isaias has developed across the southwestern Gulf this morning and is forecast to shift east/east-northeast during the next day or two, becoming more organized and strengthening to a hurricane while passing north of the Yucatan Peninsula, before turning north and tracking across the central/northern Gulf on Friday. Regardless of development, deep tropical moisture (PWATs exceeding 2 inches) will likely be drawn northward across the Southeast United States as this cyclone approaches the northern Gulf Coast early weekend, setting up the risk for heavy rainfall locally within a widespread isentropic lift scenario between a wedge of high pressure across the Carolinas/Georgia and a weak front/coastal trough nearby starting early weekend.

Widespread showers and embedded thunderstorms are possible late Friday through Sunday as the setup remains quite favorable for deep moisture transport feeding across the region between a mid-lvl pattern featuring a broad closed low over the Southern Plains and a ridge centered across the western Atlantic. This could pose an elevated risk for minor/flash flooding locally as PWATs approach 2.5 inches and rounds of precip activity occur across already wet grounds. In addition, New Moon high tides with elevated astronomical tides will occur this weekend. Any elevated rainfall rates during high tides may lead to flooding of coastal areas, including Savannah and Charleston. The latest WPC Excessive Rainfall Outlook places much of Southeast Georgia in a Marginal Risk for excessive rainfall Friday and a Slight Risk for Southeast Georgia and Southeast South Carolina on Saturday.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

VFR conditions are expected at CHS/JZI/SAV terminals through 12Z Thursday. Northeast winds could gust to around 15 kts mid morning into late afternoon, before weakening considerably this evening.

Extended Aviation Outlook: VFR through Thursday. The risk for flight restrictions returns over the weekend with widespread showers and/or thunderstorms.

MARINE

Today: The pinched pressure gradient will continue the breezy conditions this morning, with gusts of 25 to 30 knots across all near and offshore zones not including the Charleston Harbor keeping Small Craft Advisories in effect. Buoys continue to report wave heights of 5 to 7 ft across nearshore zones and up into the 6 to 8 ft range in the offshore zones, with waves starting to ease as winds decrease throughout the afternoon hours. While winds dip below Small Craft Advisory levels (25 knot gusts) throughout the afternoon and evening hours, gusts will remain in the 10 to 20 knot range throughout the overnight hours, strongest across the SE GA waters. Wave heights will similarly decrease, with Small Craft Advisories expiring from north to south.

Thursday: The last remaining 6 foot waves move out of the marine zone from Savannah to Altamaha Sound, GA 20-60nm offshore near daybreak, allowing for the Small Craft Advisory to expire. While the surface high pressure continue to weaken, the pressure gradient remains elevated with the stalled front to our south, continuing wind gusts generally in the 15 to 20 knot range.

Friday through Sunday: See NHC forecast for the latest on Tropical Depression 9. The pressure gradient will increase between a coastal trough and high pressure inland. Winds should strengthen through the period, with small craft advisories possibly needed by Friday afternoon as 25+ knot gusts move in, with gale wind gusts possible by Saturday. Strengthening winds should drive sea higher, with 6-9 ft wave heights possible on Saturday. Elevated conditions will likely persist through the rest of the weekend.

EQUIPMENT

The Metter, GA, NOAA Weather Radio Station (WWH-25) will be offline from 8 AM Wednesday, October 7, through the afternoon of Thursday, October 8. The transmitter is being relocated.

CHS WATCHES/WARNINGS/ADVISORIES

GA...High Risk for Rip Currents until 8 PM EDT this evening for GAZ217- 219-239-241. SC...None. MARINE...Small Craft Advisory until 5 PM EDT this afternoon for AMZ360. Small Craft Advisory until 8 PM EDT this evening for AMZ362. Small Craft Advisory until 2 AM EDT Thursday for AMZ364. Small Craft Advisory until 8 AM EDT Thursday for AMZ384.