Marine Weather and Tide Forecast for St. Augustine, FL

SYNOPSIS
Issued at 254 PM EDT Wed Apr 23 2025

Early afternoon surface analysis depicts Atlantic high pressure (1029 millibars) centered to the northeast of Bermuda, with this feature extending its axis southwestward across the FL peninsula.
Meanwhile, a weakening frontal boundary was stalling across the Tennessee Valley and the Carolinas
Aloft
ridging has shifted east of the FL peninsula, allowing a more zonal flow pattern developing across the southeastern states. A weak shortwave trough was embedded within this zonal flow pattern across the Deep South, with a stronger shortwave located upstream near the Arklatex region. Multi-layered cloudiness was overhead this afternoon, with a healthy cumulus field inland ahead of the Atlantic sea breeze, while pockets of cirrus and cirrostratus were drifting across our area. Breezy onshore winds for locations east of the I-95 corridor were keeping afternoon temperatures in the upper 70s to around 80, while inland temperatures were climbing to the mid and upper 80s. Dewpoints at inland locations were crashing through the upper 50s and lower 60s as of 19Z, while values in the mid to upper 60s were in place at coastal locations in the wake of the inland moving sea breeze.

NEAR TERM
(through Tonight)
Issued at 254 PM EDT Wed Apr 23 2025

Temperatures aloft will cool off through this evening as weak shortwave energy traverses southeast GA. Low level southwesterly flow will increase PWAT values to the 1.25 to 1.5 inch range at inland locations late this afternoon and evening as mid-level temperatures cool to around -15 degrees Celsius at 500 millibars (around 20,000 feet). However, it remains uncertain as to whether the inland moving Atlantic sea breeze will be enough of a trigger for convective development early this evening. Upstream convection over central AL/GA may send outflows southeastward across the Alapaha/Ocmulgee/Altamaha Rivers by around sunset, but short-term, high resolution models continue to indicate only isolated convection developing for locations west and north of Waycross into the early evening hours. The inland moving Atlantic sea breeze may collide with the Gulf coast sea breeze this evening along the I-10 corridor to the west of U.S. Highway 301 to create isolated convection, but higher coverage is expected to remain across interior southeast GA. Although bulk southwesterly shear values around 30-35 knots will be modest, colder mid-level temperatures working into our region later today could cause a few storms to pulse and become strong, mainly for locations west and north of Waycross. Downburst winds of 40-50 mph, small hail, and cloud to ground lightning strikes will be the primary hazards with this activity this evening.

Any convection that manages to develop this evening should dissipate by midnight, with patchy to areas of fog possible towards sunrise, mainly for inland southeast GA. Otherwise, high pressure strengthening along the Mid-Atlantic and New England coasts later tonight may provide enough convergence to produce a few coastal showers towards sunrise. Lows tonight will range from the lower 60s inland to the mid and upper 60s at coastal locations, where a light southeasterly breeze will continue overnight and early Thursday morning.

SHORT TERM
(Thursday through Friday night)
Issued at 254 PM EDT Wed Apr 23 2025

An overall persistent pattern will continue through the short term period, which will feature high pressure in the low levels to the north and east of the region as a backdoor cold front weakens and essentially dissipates to our north. Thursday, the onshore sea breeze progressing inland as well as some possible lingering outflow boundaries from Wednesday Evening/Night convection could be enough for a few showers and thunderstorms to develop, especially over inland southeast GA as plenty of dry air lingers in the mid levels, especially over northeast FL. In addition, a mid level impulse moving across north and central GA Thursday evening will also provide some marginal lift/dynamics for convective initiation where moisture is sufficient. Generally above average temperatures continue Friday, especially away from the coast where mid to upper 80s will be expected and perhaps a few readings in the 90s. Low 80s will be more common east of about I-95. Some convective activity will likely linger Thursday Night as well as mid and high clouds with mild lows in the 60s area- wide.

High pressure remains in control Friday, though a fairly strong moisture gradient will persist aloft as the high pressure ridge will be draped across the Florida peninsula. Therefore, southeast GA will once again have the best chance for isolated showers or thunderstorms Friday afternoon and evening, though expecting these chances to be lower than Wednesday and Thursday - generally in the 10% range north of about I-10. Temperature wise will be very similar Friday and Friday Night: Mostly in the mid to upper 80s to near 90 inland and low 80s east of I-95 to the coast, falling mostly into the 60s Friday Night.

LONG TERM
(Saturday through next Wednesday)
Issued at 254 PM EDT Wed Apr 23 2025

High pressure will start to break down on Saturday as a stronger cold front starts to approach from the north, moving across the region Saturday Night and through Sunday and south of the region by Monday and Tuesday. The front will bring increased chances for showers and thunderstorms for most of the region, especially Sunday and into Monday. High pressure wedges down the eastern seaboard Sunday Night and Monday before the associated high moves off the Carolinas and resume its position north and east of the region. This will return a more northeast to southeasterly onshore flow towards the end of the long term period after a weaker flow Saturday and Saturday Night. Temperatures will remain near normal for most of the long term period with the main exception being Monday post cold front in a stronger flow from the northeast to east, quickly starting to moderate again Tuesday with veering flow.

AVIATION
(00Z TAFS)
Issued at 701 PM EDT Wed Apr 23 2025

Patchy fog is expected to develop overnight, which could produce restrictions, mainly toward dawn. This fog will lift after sunrise Thursday, with VFR conditions from mid morning through the afternoon.

MARINE
Issued at 254 PM EDT Wed Apr 23 2025

High pressure building to the north of a stalled front will briefly wedge down the southeastern seaboard on Thursday afternoon, creating breezy onshore winds through Thursday evening.
This high pressure center will push offshore of the Mid-Atlantic and New England coasts on Thursday night ahead of a cold front that will move across the southeastern states on Saturday afternoon and evening. This front may bring scattered showers and thunderstorms to our local waters from Saturday night through Monday. Seas of 2 to 4 feet will prevail both near shore and offshore through Saturday night.

Strong high pressure building over the Great Lakes states in the wake of this front during the weekend will shift towards the southeastern seaboard early next week, with winds shifting to northeasterly and strengthening across our local waters by Sunday afternoon, with seas expected to gradually build to Caution levels of 4 to 6 feet offshore from Sunday through Monday. Seas near shore will build to the 3-5 foot range.

Rip Currents: A persistent easterly ocean swell will combine with breezy onshore winds will keep a lower end moderate risk in place at all area beaches through the upcoming weekend. A high risk is possible early next week as onshore winds strengthen and surf becomes increasingly rough.

FIRE WEATHER
Issued at 1235 PM Wed Apr 23 2025

Scattered showers and thunderstorms are expected to develop late this afternoon and early this evening and again on Thursday afternoon and evening across inland portions of southeast GA and possibly northern portions of the Suwannee Valley. Activity should become isolated across these inland locations on Friday afternoon and evening. Otherwise, increasingly hot temperatures at inland locations will drop minimum relative humidity values to the 30-35 percent range for locations west of I-95 corridor this afternoon and again on Thursday afternoon. Breezy easterly surface and transport winds will overspread the I-95 corridor this afternoon, and fair to good daytime dispersion values are forecast area-wide.
Breezy easterly surface and transport winds will develop during the late morning hours at coastal locations on Thursday, with these winds spreading inland during the afternoon hours, creating mostly good daytime dispersion values across our region. Elevated mixing heights and southeasterly surface and transport winds on Friday will create good daytime dispersion values at most locations on Friday, with marginally high values possible across north central FL.

CLIMATE
Issued at 1235 PM Wed Apr 23 2025

DAILY RECORD HIGHS

WED THU FRI SAT SUN

JAX 92 (1970) 93 (1999) 92 (1958) 92 (2011) 94 (1986)

GNV 92 (1970) 94 (1999) 93 (1896) 93 (1908) 96 (2011)

AMG 94 (1968) 93 (1999) 91 (1958) 93 (1986) 96 (1986)

CRG 89 (2020) 92 (1999) 91 (2006) 91 (1989) 93 (2011)

PRELIMINARY POINT TEMPS/POPS
AMG 62 86 61 86 / 40 40 10 10 SSI 67 80 67 80 / 10 10 0 10 JAX 62 85 62 85 / 10 10 0 10 SGJ 66 81 66 81 / 10 0 0 0 GNV 61 89 61 89 / 10 10 0 0 OCF 61 90 60 90 / 10 0 0 0

JAX WATCHES/WARNINGS/ADVISORIES
FL...None.
GA...None.
AM...None.