Marine Weather and Tide Forecast for St. Augustine South, FL

NEAR TERM /THROUGH TONIGHT/
Main Highlights through Tonight:

- Heat Advisory Conditions Continue Area-Wide Today.

- Isolated Strong Thunderstorms this afternoon and early evening, Mainly Across Southeast GA and the Interstate 10 Corridor.

Not much change in the ongoing forecast as mid/upper level ridge aloft and surface trough development along the I-95/US-301 corridor which will draw in the East Coast sea breeze just enough to trigger scattered showers and storms this afternoon and evening, mainly from the I-10 corridor northward across SE GA, where a few isolated strong storms are expected with gusty winds of 40-50 mph and heavy downpours with a localized flood threat due to slow and erratic storm motion 10 mph or less, with a quick 1-3 inches possible in the more intense storms. Convection will fade after sunset and end around midnight for most locations before it drifts into the Atlantic. Dew point temps slightly higher this afternoon into the mid/upper 70s, so combined with Max temps into the mid/upper 90s still expect the Heat Advisory in effect to verify with peak heat indices mostly in the 108-112F range. Overnight lows still on track for mid/upper 70s inland and around 80F for the Atlantic Coast and along the St. Johns River.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/
Main Highlights This Period:

- Isolated Strong to Severe Storms Monday & Tuesday Afternoon/Evening, Especially for Northeast FL

- Heat Index Values Near or Above Heat Advisory Each Day

A frontal boundary from out of the northwest will settle in over southeast Georgia by Monday resulting in more inhibited convection over southeast Georgia and with higher chances for storms occurring ahead of the boundary over northeast Florida. Prevailing flow will shift to become more out of the west and northwest with moist air maintaining over northeast Florida south of the frontal boundary and north of high pressure ridging crossing over the southern Florida peninsula, with PWAT values measuring upwards of over 2.5 inches.
High temperatures for the beginning of next week will rise into the upper 90s and potentially reaching upwards to 100 over portions of southeast Georgia. Overnight low temperatures will drop down into the mid to upper 70s over inland areas and in the upper 70s and lower 80s for coastal areas and along the St Johns River. Heat index values during this period will reach upwards of 106 up to over 113, resulting in heat advisory and possible extreme heat conditions through Tuesday.

LONG TERM /WEDNESDAY THROUGH SUNDAY/
Main Highlights This Period:

- Hazardous Heat Continues Next Week

- Isolated to scattered thunderstorms each afternoon and evening, some which could become strong

Prevailing flow will shift to become more out of the northwest by the end of the week as the stalled frontal boundary over southeast Georgia, which had been acting to inhibit convection for portions of the northern forecast area through much of the week, begins to disperses and move off to the northeast and results in a more uniform pattern of diurnal convection going into the weekend. High temperatures will continue to be in the upper 90s through next week with heat index values likely to reach heat advisory levels through the end of the week.

AVIATION /18Z SUNDAY THROUGH 18Z MONDAY/
More significant Cu development this afternoon and slight increase in Hi-Res guidance rainfall chances suggests the need to include PROB30 groups in the 19-23Z time frame for potential MVFR conds in TSRA activity along with potential for gusty winds as the East Coast sea breeze pushes inland past SSI/CRG/SGJ and helps to trigger widely scattered storms near local terminals. This activity should fade after 00Z, with lingering VFR mid/high level clouds into the overnight hours. Not much chance at any fog around sunrise Monday morning so will continue to leave out of the forecast for now.
Overall rainfall chances for Monday will be after the current end time of 18Z TAF period, so will leave out for now as well.

MARINE

Atlantic high pressure will continue to extend its axis westward across the Florida peninsula, creating a prevailing westerly wind pattern across our local waters. A frontal boundary will then push into the southeastern states by Monday afternoon, with this feature stalling just north of the Georgia waters by midweek. Chances for mainly afternoon and evening thunderstorms will increase across our local waters during the work week. Southwest to westerly winds will continue to prevail, with brief evening surges of wind speeds to Caution levels through the work week.

Rip Currents: A lower end moderate risk this afternoon at area beaches as the sea breeze creates an onshore flow that will combine with the outgoing tide and a persistent long period southeasterly ocean swell. Prevailing offshore winds will strengthen on Monday and Tuesday, creating a low risk that will likely continue through the end of the work week at all area beaches.

FIRE WEATHER
- Heat Advisory In Effect Today - Patchy High Dispersions Inland Southeast Ga Monday And Tuesday

Hot conditions are expected to persist through the rest of the weekend and into at least the start of next week, with Heat Advisories likely and possibly even Extreme Heat Warnings possible each day for most or all of the region. This will come with a flow direction generally out of the southwest to west through the next several days except for a wind shift with the sea breeze generally east of the I-95 corridor. A frontal boundary dropping southward tonight and Monday will return more "usual" chances for showers and storms for all today, then mainly over northeast Florida for early to mid week as some drier air moves into southeast GA behind the front. Better mixing and transport winds will result in good to patchy high dispersions over inland GA, with fair to good dispersions elsewhere. The front will linger just north of the region by late week, with shower and storm chances generally increasing as well.

Fog Potential: Significant fog developments are not expected, however late-night or early-morning fog developments are expected to be shallow and patchy, mainly occurring over areas that have received locally heavy rainfall. Gusty and erratic winds are often possible within and nearby any stronger showers or storms.

CLIMATE
Near record high temperatures are possible at some of our designated climate sites during the next several days:

Sunday, August 16: KJAX: 97/1957 KGNV: 97/1918 KAMG: 100/1995 KCRG: 95/2022

Monday, August 17: KJAX: 99/1954 KGNV: 97/1954 KAMG: 104/1995 KCRG: 97/2005

Tuesday, August 18: KJAX: 98/1954 KGNV: 98/1954 KAMG: 105/1995 KCRG: 96/2023

PRELIMINARY POINT TEMPS/POPS
AMG 76 97 78 98 / 20 10 0 10 SSI 79 97 80 98 / 30 20 10 20 JAX 77 95 77 96 / 30 40 20 30 SGJ 77 95 78 96 / 30 50 20 40 GNV 76 94 77 95 / 20 50 20 60 OCF 75 95 77 96 / 10 50 10 70

JAX WATCHES/WARNINGS/ADVISORIES
FL...Heat Advisory until 8 PM EDT this evening for FLZ021-023-024- 030-031-035-038-120-124-125-132-136>138-140-220-225-232- 233-236-237-240-322-325-333-340-422-425-433-522-533-633.
Heat Advisory from 11 AM to 8 PM EDT Monday for FLZ021-023-024- 030-031-035-038-120-124-125-132-136>138-140-220-225-232- 233-236-237-240-322-325-333-340-422-425-433-522-533-633.
GA...Heat Advisory until 8 PM EDT this evening for GAZ132>136-149- 151>154-162-163-165-166-250-264-350-364.
Heat Advisory from 11 AM to 8 PM EDT Monday for GAZ132>136-149- 151-152-162-163-250-264-350-364.
Extreme Heat Warning from 11 AM to 8 PM EDT Monday for GAZ153- 154-165-166.
MARINE...None.