Marine Weather and Tide Forecast for Sebastian, FL

DISCUSSION
Issued at 515 AM EDT Fri Oct 4 2024

Today-Tonight...A stream of scattered, locally heavy rain showers continues to move onshore along the Treasure Coast this morning.
Recent CAM guidance has backed off on the higher rain accumulations that were once (persistently) being advertised.
However, a quick 1 to 2 inches of additional rainfall remain possible where training showers set up. Farther north, dry conditions prevail with temperatures in the 70s to low 80s at the coast.

Onshore flow will be gusty at times, especially this afternoon, as a diffuse coastal breeze pushes inland. Along this feature, isolated showers and a few lightning storms are forecast. A sharp moisture gradient will bisect the area from northwest to southeast, keeping locations farther north and east drier (i.e.
Melbourne/Daytona Beach). Therefore, the highest rain chances this afternoon and evening exist from Stuart and surrounding Lake Okeechobee locations, northwest to Orlando and Leesburg (25-40 percent). Occasional lightning strikes and gusty winds to 40 mph will be the main concern, though a lack of deep moisture and instability should keep most of any storm activity at bay. Some cloud cover will hold across the western half of the area, eventually pushing back toward the Atlantic coast late tonight before clearing.

High temperatures this afternoon will be warm again, peaking around 90 degrees inland and in the mid to upper 80s east of I-95.
Lower humidity, especially north, will keep heat index values in the mid to upper 90s. Farther south, values may peak in the low 100s. Overnight lows will fall into the mid 70s for most.

A high risk of rip currents also exists at the beaches today, likely lasting into the weekend and next week, as persistent east-northeast winds create increasingly rough surf. Entering the surf is strongly discouraged.

Saturday-Sunday...We look to start the weekend slightly warmer than normal with highs in the upper 80s to around 90 degrees and finish Sunday with highs near or slightly below normal.
Synoptically, the weak influence of high pressure on Saturday will be eroded moreso by an approaching front on Sunday. This front effectively slows down over north FL and south GA on Sunday as a warm front surges north across the FL Peninsula. South of the warm front, deep moisture advection returns to south-central FL by Sunday afternoon/evening.

In short, Saturday will be the drier of the two weekend days.
Something to watch Saturday afternoon will be the formation of showers and isolated storms over the local Atlantic, as some of this activity could push onshore later in the day. For now, a widespread 15-25 PoP was maintained, as the setup is not very impressive due to a lack of moisture and forcing. By Sunday, with the approach of two competing fronts and a return of 2"+ PW over much of the area, rain and storm chances notably. This is especially true for locations near Melbourne and southward to Lake O and the Treasure Coast. Locally heavy rainfall is possible across the southern third of the forecast area Sunday afternoon into early next week. At the beaches, a high risk of rip currents will continue.

Monday-Thursday...Near to below normal temperatures are forecast next week, thanks to quite a bit of cloud cover and areawide rain chances. Models indicate a stationary boundary will set up somewhere across the central or southern FL Peninsula and stay in place until later Wednesday or Thursday before drifting farther south. At least one or two disturbances are expected to ride along the front, crossing the state of FL and bringing the chance for repeated rounds of heavy rainfall to the area. The National Hurricane Center continues to highlight an area of potential tropical cyclone development in the southern Gulf of Mexico, which some models and their ensemble members bring across south FL midweek. Whether a low pressure system takes on tropical characteristics or not, it is clear that heavy rain and flooding potential will be increasing as the week wears on. Exact locations and amounts are to be determined, though the southern half of east central Florida will be likely be favored for higher rain totals.
This is where the Weather Prediction Center is highlighting a Marginal Risk for excessive rainfall Monday and Tuesday (D4/D5).

In addition to the heavy rain threat, increasingly breezy conditions are forecast from Tuesday onward. Gusty east- northeast winds will lead to rough surf and a continued threat for numerous, strong rip currents.

MARINE
Issued at 515 AM EDT Fri Oct 4 2024

Today-Tonight...Scattered showers will continue this morning, mainly south of Sebastian Inlet. Easterly winds 10-15 kt with gusts up to 20 kt are forecast, especially as a diffuse coastal breeze moves inland this afternoon. Seas 3-5 ft, perhaps up to 6 ft well offshore, decreasing to 2-4 ft (5 ft offshore) tonight.

Saturday-Tuesday...Increasing long period swells from distant Major Hurricane Kirk will create poor to hazardous boating conditions Saturday night through the early part of next week.
Seas reach 4-6 ft nearshore, up to 7 ft offshore late Saturday into Sunday, building as high as 8 ft by Monday. Wave heights remain poor/hazardous on Tuesday, building further Tuesday night as a local pressure gradient strengthens over the waters. Of note, the Gulf of Mexico is being monitored for potential tropical development next week. Regardless of development, rain chances, seas, and winds will be increasing locally from Tuesday onward.

AVIATION
(06Z TAFs)
Issued at 150 AM EDT Fri Oct 4 2024

Ongoing VCTS along the Treasure Coast overnight as onshore flow prevails. Kept out TEMPOs for now, but would not be surprised if amendments are needed and they are added in at some point throughout the night. Mostly dry elsewhere. Increasing VCSH and VCTS chances after 15Z across the terminals with onshore flow increasing to around 10 knots. May have to evaluate the need for TEMPOs with the next package. Activity is forecast to diminish after 21Z along the coast and after 00Z across the interior terminals.

HYDROLOGY
Issued at 515 AM EDT Fri Oct 4 2024

River levels along the Saint Johns at Astor are forecast to very slowly decline this weekend into next week. However, additional heavy rainfall forecast over the basin could alter the river's decline. The river point at Geneva (Above Lake Harney) is also forecast to see rises into next week, potentially reaching Action Stage by Monday.

PRELIMINARY POINT TEMPS/POPS
DAB 88 76 87 75 / 20 10 30 30 MCO 89 75 88 75 / 30 10 20 30 MLB 88 77 87 76 / 20 10 20 30 VRB 88 76 88 76 / 30 10 20 30 LEE 90 75 88 75 / 30 10 20 20 SFB 89 75 88 75 / 20 10 20 30 ORL 89 76 89 76 / 20 10 20 30 FPR 88 76 88 75 / 40 10 20 30

MLB WATCHES/WARNINGS/ADVISORIES
FL...None.
AM...None.