Marine Weather and Tide Forecast for Port St. John, FL

DISCUSSION
Issued at 145 AM EDT Mon Aug 3 2026

-----------Synoptic Overview-----------

Early this Monday morning, a positively tilted trough extends from Lake Erie to Louisiana. This has maintained a break in the large-scale ridging across the W Atlantic and the Desert Southwest. Over the next 48 hours, the southern extent of this trough will become cut off from the mid-latitude westerlies as it stalls over Georgia and Alabama. This will help to keep negative surface pressure anomalies over the Deep South and preserve a southwesterly or southerly background flow regime over Florida through at least Tuesday. Therefore, the ribbon of tropical moisture, with PWAT values exceeding 2 inches, should remain anchored over the Florida Peninsula early this week.

Beginning Wednesday, the W Atlantic ridge is poised to strengthen and become centered offshore of Cape Hatteras. As this occurs, an axis of surface high pressure should lift north of Central Florida, allowing onshore flow to resume for the latter half of the work week. Moisture is expected to briefly return to near-normal levels.

Beneath the sprawling Bermuda high, the 02/12Z ensemble suite continued to track an inverted trough westward across the Atlantic this week. Led by the EPS and GEPS, 70-75% of the members push this feature near or directly over Florida. The remaining members recurve the disturbance east of Florida. With the favored solution, a combination of positive vorticity and moisture advection would reach our area beginning Friday through at least Saturday.

Thereafter, there is substantial confidence that the strong Bermuda high will hold just off the east coast of the U.S. by Sunday and next Monday. Surface ridging should remain near or north of Central Florida, with moisture values close to normal.

-------Sensible Weather & Impacts-------

Today - Tuesday...

Given the abundant moisture and sufficient destabilization that is expected each day, 50-70% rain and storm chances will continue early this week.

While a few showers or a rogue storm may form over our northern communities through the morning, hi-res guidance indicates that the highest chance for storms today may reside just south of I-4, where better heating is forecast. Northeast-moving storms and outflows may interact with a pinned sea breeze south of Cape Canaveral to enhance coverage and intensity along the coast late this afternoon or early evening. As in recent days, a few gusty storms should be anticipated, with wind gusts from 45 to 50 mph in the heaviest activity. There is a 5-10% chance of rainfall amounts of 3-4 inches, which may cause minor flooding in poor drainage areas.

Much of the area should dry out overnight, except for a low chance for showers west of Orlando. On Tuesday, storm motions should be slower but still favor a northeastward movement as mid-level flow remains weakly offshore. Similar to today, we should see a sea breeze form and move just a bit farther inland (near and west of I-95, south of the Cape). This should focus another round of showers and storms in the afternoon and early evening.

Expect a bit more sunshine, which should allow temps to heat back into the lower 90s. Heat indices top out from 100-106 in most spots.

Wednesday - Thursday...

SE to E flow returns for midweek as high pressure lifts northward.
As the Atlantic sea breeze becomes more dominant, coastal areas should anticipate a few showers and storms through early afternoon before activity shifts over the interior. Near-normal moisture levels will support 40-60% storm chances along the coast, rising to 60-80% farther inland. Seasonably hot and humid weather will prevail outside of the storms.

Friday - Weekend...

As mentioned in the overview, the favored solution is for the next disturbance to bring more energy and moisture off the Atlantic and across the state from Friday through at least Saturday. We may begin to see onshore-moving showers at night and in the morning, with storms developing over the interior and western Florida by afternoon. As of now, our rain/storm chances are 50-70% near and north of Orlando and as high as 60-80% to the south on Friday and Saturday. Will need to monitor the potential for locally heavy rainfall amounts, particularly if the trough is sharper and more pronounced as it approaches.

By Sunday and Monday, it does appear this energy should be lifting away from the area, returning us to more typical summertime conditions with at least scattered daily storm coverage.

The risk of life-threatening rip currents is forecast to increase at our beaches late this week as onshore flow increases.
Temperatures and humidity levels remain largely unchanged through the weekend, with near-normal conditions likely.

MARINE
Issued at 145 AM EDT Mon Aug 3 2026

A weakening cold front is draped across the Deep South, keeping an axis of high pressure south of the local Atlantic. Mariners should again be watching the western sky for offshore-moving showers and storms today and Tuesday. Beginning Wednesday, high pressure begins to lift northward, pushing north of the waters on Thursday. Onshore flow will develop, with a dominant Atlantic sea breeze in the afternoon. Winds are likely to freshen out of the east late in the work week as a trough approaches from the open Atlantic.

South to southwest winds 8-15 kt today, perhaps turning southeasterly at the coast south of Cape Canaveral late. Winds become SSE on Tuesday and SE on Wednesday, 5-12 kt. Winds turn easterly on Thursday and begin to freshen, 10-15 kt. Seas 1-2 ft nearshore, up to 3 ft offshore, through Wednesday. By Thursday, seas build to 2-3 ft nearshore and up to 4 ft offshore late.

AVIATION
(18Z TAFs)
Issued at 120 PM EDT Mon Aug 3 2026

A bit of a tricky forecast for the remainder of the day, as earlier showers and cloud cover seem to have limited the threat for TSRA from ISM/MCO northward. Nevertheless, a few lightning strikes cannot be ruled out this afternoon, so have included prevailing VCSH with TEMPOs for embedded TSRA affecting the terminals, before tapering off this evening. Cannot rule out a few stray showers overnight, but confidence is low. Instead, the greatest chance for convection appears to be along the coast from MLB southward, generally from 19-23Z, when TEMPOs have been included. VCSH looks to continue there through around 2Z, before tapering off. SW flow 9-12 kts, with gusts up to 20 kts, backs S/SSE along the coast with the sea breeze.

An unsettled pattern looks to persist into Tuesday, with a few rounds of showers possible.

PRELIMINARY POINT TEMPS/POPS
DAB 74 90 74 89 / 20 60 20 50 MCO 75 91 75 91 / 20 50 20 60 MLB 75 90 76 89 / 30 60 20 40 VRB 73 90 74 89 / 40 60 30 50 LEE 75 90 75 91 / 30 60 10 60 SFB 76 92 75 91 / 20 50 20 60 ORL 76 91 76 91 / 20 50 20 60 FPR 73 90 74 88 / 30 50 30 50

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