textproduct: Jacksonville

KEY MESSAGES

For the latest NE FL and SE GA Daily Key Messages please visit: https:/www.weather.gov/media/jax/briefings/nws-jax-briefing.pdf

- High Rip Current Risk Today all Local Beaches

- Daily Afternoon & Evening Thunderstorms Through. Main Hazards: Locally Heavy Rain, Lightning & Gusty Winds

NEAR TERM /THROUGH TONIGHT/

Main Highlights through Tonight:

- Passing gusty showers & inland mainly afternoon storms

Scattered showers will push onshore through the rest of the early morning hours with the continuing onshore flow. Throughout the day, the lingering frontal boundary over central FL will try to lift a bit north as a warm front, but likely will remain just over north central FL as high pressure begins to extend across the southeastern US. With the onshore flow persisting for another day, similar pattern of showers and storms will push from east to west reaching the far interior locations by the afternoon hours. While not as elevated as yesterday, could still see some gusts reaching into the 20 mph range outside of any showers or storms that develop during the afternoon hours, with the strongest closer to the coast. By the overnight hours, winds will steadily begin to veer and become southerly then southwesterly by Thursday with high pressure shifting towards the Atlantic.

Daytime highs will mainly sit in the upper 80s to lower 90s with the cooler temperatures along the coast thanks to the onshore flow. By the overnight hours, temperatures will sit in the 70s with warmer temperatures along the coast in the upper 70s.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/

Main Highlights This Period Thursday through Friday Night:

- Summer-like Pattern Returns

- Daily Isolated Strong Afternoon & Evening Storms

- Localized, Briefly Flooding Rain Risk Inland Areas

Surface high pressure builds offshore of the Carolinas Thursday while a strong 500 mb ridge positions across GA and N FL early, then shifts farther offshore of the Florida coast into the afternoon. This regime will bring SSE steering flow and less morning coastal showers compared to recent days as low level convergence weakens. Elevated moisture with precipitable water 2-2.4 inches across the area combined with weak steering flow < 10 kts will enable both Gulf and Atlantic coast sea breezes to develop, with showers and thunderstorm activity increasing in coverage across the area into the afternoon as the sea breezes move inland. Boundary mergers will focus across inland areas between I-75 and Highway 301 into the early evening, where the higher rain chances of 60-80% were advertised. Inland early evening convection may begin to drift back toward the Atlantic coast as SW steering flow develops as the mid level ridge positions east of Florida. Given high moisture, the main hazard will be locally heavy rainfall but also isolated strong to pulse severe storms with gusty wet downbursts will be possible in boundary mergers during the mid afternoon into the early evening, especially across inland areas.

Friday, the surface ridge axis extends across south FL with the upper level ridge farther to the east. This pattern will transition steering flow to the SSW and bring a dominant west coast sea breeze convective regime. Midday showers and isolated storms will begin to form along both the Atlantic & Gulf Coast sea breezes, with a merger shifted slightly more toward the east compared to Thursday in the afternoon roughly near Highway 301 and the St. Johns River basin. Resultant storms will tend to track back toward the Atlantic coast into the evening under the westerly steering flow. High moisture continues across the area Friday with PWAT 2.3-2.5 inches across much of FL and coastal SE GA with slightly lower PWAT across inland SE GA near 2 inches. This high moisture combined with weak flow will continue a localized flooding rainfall risk given weak storm motion and also the risk of wet downbursts especially near storm and boundary mergers in the mid to late afternoon across inland areas.

Temperatures will trend above average with highs in the lower 90s for most inland locations to upper 80s to near 90 at the coast. Daily peak heat index values will range from the upper 90s up to 105 deg for inland locations. Muggy overnight lows will range in the low/mid 90s.

LONG TERM /SATURDAY THROUGH TUESDAY/

Main Highlights This Period Saturday through Wednesday:

- Above Average Temperatures & Daily Thunderstorms this Weekend

- Elevated Rip Current Risk Tuesday & Wednesday

The 1000-500 mb mean layer ridge axis pivots northward from south Florida this weekend and extends across the local area by Sunday with higher PWAT of 2+ inches overspreading the area from the south once again. With the weak flow, daily Gulf and Atlantic coast seas breezes will develop by midday and trigger showers and storms with a merger across inland areas late afternoon and into the evening.

Monday, the ridge axis lifts farther north and strengthens through Wednesday, which will bring a return of easterly flow across the local area. The surface ridge axis positions across the local area as well at least Monday & Tuesday, with coastal troughs south of the local waters. By Wednesday, the surface ridge weakens and shifts more to the northeast, allowing coastal troughs to begin to develop over the adjacent coastal waters mid to late week, with an increase in breezy onshore/east winds and coastal shower activity. A more dominant east coast sea breeze pattern will develop with the better chances of afternoon storms focused across inland zones into the late afternoon.

Temperatures will moderate back more toward average highs for this time of year in the mid to upper 80s with the return of easterly flow with lows still ranging in the 70s.

With the return of easterly winds next week, local rip current risk will also become elevated once again.

AVIATION /06Z WEDNESDAY THROUGH 06Z THURSDAY/

Lower stratus is filtering across the area, as MVFR CIGS will be possible for CRG/JAX while LIFR CIGS at VQQ/GNV from 08-12Z. With onshore flow persisting, showers are expected to push across TAF sites around the 13-15Z time frame with mostly MVFR CIGS that will become VFR by the 16-18Z time frame. Left mention of isolated TSRA VCTS) at all terminals between 16-22Z with PROB30 groups with MVFR CIGS/VSBYS and gusty winds to 25-30 knots with mostly SHRA activity.

MARINE

A coastal trough sits over the local waters Today as of gusty showers and isolated thunderstorms push towards coastal locations. Easterly winds Today will gradually lessen as the trough begins to weaken by late Tonight with high pressure building northeast of the region. The high will then extend across the Florida peninsula Thursday with southerly winds and a return of southwest winds Friday into the weekend with the afternoon east coast sea breeze.

Onshore easterly winds continue as surf heights near 3-4 ft Today. A High rip current risk for all local beaches is in place through Today. Veering winds with lower surf heights will bring reduced chances of rip currents on Thursday.

FIRE WEATHER

Breezy east winds continue today with waves of morning coastal showers and isolated thunderstorms. Rain chances shift farther inland into the afternoon with the higher chances of afternoon and early evening thunderstorms west of Highway 301 and toward Interstate 75. Winds become southeast tonight with less coastal shower activity Thursday morning. Both Gulf Coast and Atlantic Coast sea breezes develop Thursday afternoon, with showers and storms developing along and between these inland progressing boundaries. The sea breeze merger is expected Thursday afternoon across inland areas. Humidity will remain above critical values and daytime dispersion will be generally good today and then fair to generally good on Thursday due to weaker transport winds.

Fog Potential: Gusty and erratic wind shifts will occur from thunderstorm activity. Patchy fog is expected across inland southeast GA and portions of inland northeast Florida Thursday morning. Widespread dense fog is not expected at this time.

HYDROLOGY

Coastal water levels peaked yesterday evening along the Atlantic coast and near the mouth of the St. Johns River into the high end Action Stage to Minor flood for coastal southeast GA where the onshore flow was strongest. Water levels will remain elevated over the coming days with the approach of the New Moon on Sept 11th and range primarily in the Action stage for both coastal and St. Johns River locations with minimal impacts.

PRELIMINARY POINT TEMPS/POPS

AMG 89 73 91 73 / 50 10 50 20 SSI 88 78 89 77 / 60 10 20 30 JAX 89 75 91 74 / 40 10 50 20 SGJ 87 76 89 75 / 30 10 40 20 GNV 90 73 91 73 / 60 10 60 20 OCF 91 74 92 74 / 60 30 60 20

JAX WATCHES/WARNINGS/ADVISORIES

FL...High Risk for Rip Currents through this evening for FLZ124-125-138- 233-333. GA...High Risk for Rip Currents through this evening for GAZ154-166. MARINE...None.