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

- Coastal & Marine Hazards Continue through the Weekend. Small Craft Advisory through Saturday Night. High Risk for Rip Currents, Rough Surf, Elevated Tides and Beach Erosion. Minor Tidal Flooding Continues for the St Johns River

- Hurricane Isaias tracking northward toward northern Gulf coast. Reinvigorated onshore Winds and Additional Periods of Heavy Rain Friday and Saturday. Isolated Severe Thunderstorms/Tornadoes Possible Friday night through

NEAR TERM /UNTIL 7 AM FRIDAY MORNING/

Main Highlights Today and Tonight:

- Coastal and Marine Impacts Continue, Including Coastal Flood Warning for Upstream St. Johns River. High Risk of rip currents and increasing easterly winds for area coastal waters tonight.

- Numerous showers and isolated embedded thunderstorms across northeast and north central FL through tonight. Isolated flash flooding possible for north central FL into late evening.

Latest mesoanalysis shows northeasterly flow over the region with a frontal boundary nearly stationary over central FL area. This front will start to work back northward late tonight. Not much instability is noted at 1 PM with 400-800 ML CAPE across northeast FL. Areas to widespread showers will continue to develop over northeast FL through tonight due to isentropic processes, with a few embedded thunderstorms possible. Some localized heavy rainfall, and localized flooding is possible for northeast FL where rainfall amounts may reach upwards of 1-3 inches in some spots. Given the look of the radar imagery and the guidance, have opted to go with a flood watch for south portions of the forecast area through late tonight. Generally looks like moderate to sometimes heavy rainfall potential is best through the late evening and then begin to taper off to a light to an occasional moderate rain after midnight. Breezy northeast to east winds and elevated seas will continue to support the high rip current risk, elevated surf, and elevated water levels both at the coast and the along the St Johns River basin. Water levels upwards of 2 ft MHHW will be possible for the coastal areas, solidly in the minor flood category.

SHORT TERM /7 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/

Main Highlights This Period: Friday through Saturday night

- Potential for strong to severe storms increasing through Saturday, along with flooding chances

- Strong onshore winds renew the surf zone risk and continue tidal flooding within the St Johns River and along the Atlantic coast.

As hurricane named Isaias will move north across the Gulf Friday. As it moves north, it will push the warm front north into north central FL as a warm front. The combination of lift along and north of the warm front, combined with outer bands will provide for a stormy day, especially for NE FL. While the greatest chance for severe weather will be to the west of the area, closer to the track of the Hurricane, it can not be ruled out locally due to the warm front. Due to the cloud and precipitation coverage, temperatures will be a little below average Friday.

The warm front will lift across, then to the north of the area Friday night, as the Hurricane moves inland. Above average precipitation chances will continue as the front lifts through. Can not rule out a stronger storm due to the warm front.

On Saturday, with the warm front to the north, warm and more moist air will advect north into region. This will bring above average temperatures and continued high chances for precipitation. The chance for strong to severe storms will increase during the day Saturday.

Precipitation chances will be lower Saturday night, but potential will still exist especially across SE GA.

LONG TERM /SUNDAY THROUGH THURSDAY/

Main Highlights This Period: Sunday through Thursday

- Potential for strong to severe thunderstorms Sunday

The cold front trailing from remains of Tropical system will move east southeast across area Sunday through Sunday night. An unseasonably warm airmass will be in place ahead of the passage, along with ample moisture. The combination of these factors will lead to above average convective potential Sunday, with potential for strong to severe storms.

A drier airmass will settle south across the area next week as high pressure builds. Temperatures will remain above average through the week.

AVIATION /00Z FRIDAY THROUGH 00Z SATURDAY/

MVFR or near MVFR conditions are expected to continue across the area through tonight as the onshore flow regime persists and mainly light to moderate rainfall also will remain ongoing. Some TEMPO groups may be needed overnight for heavier rainfall in any localized convergence bands, though confidence in coverage is too low to include any at this time. Winds pick up during the day Friday as the gradient between onshore flow and Hurricane Isaias over the Gulf strengthens. This will also rotate more bands of showers and embedded thunderstorms as well, with confidence high enough to include PROB30 groups at all terminals. These will be refined as we get closer, and likely include potential for gusty winds in stronger showers and thunderstorms thanks to the tropical influence. These factors, along with reduced vsbys and lower ceilings, will be the main impacts from the Hurricane as it passes well to the west of the region.

MARINE

East northeast winds and seas support small craft caution conditions for most of the area waters today. A front will lift northward through the waters starting tonight with another high pressure center building in north of the region Friday and to the north northeast on Saturday. Small Craft Advisory conditions will return due to elevated easterly winds and seas beginning tonight and Friday and continue through Saturday night.

The National Hurricane Center is monitoring Hurricane Isaias in the central Gulf. This system is expected to move northward towards the central Gulf coast region Friday into Saturday. Showers and thunderstorms will increase in coverage throughout our local waters during the weekend as tropical moisture surges northward on the eastern periphery of this tropical system.

Rip Currents: A moderate northeast wind and lingering wind-sea state today will support dangerous rip currents and rough surf. High Rip Current Risk will likely continue through this weekend with continued breezy/windy onshore flow.

FIRE WEATHER

- Patchy High Dispersions Monday

A warm front will stretch east across central FL through Friday. This front will lift north of the area Friday night, as Hurricane Isaias makes landfall over the northern Gulf coast. A cold front will move southeast across the area Sunday into Sunday night. Above average precipitation chances through Sunday, with potential for strong to severe thunderstorms. The greatest chance for severe storms will be on Saturday. In addition, flooding potential will continue through Sunday.

High pressure will provide mainly dry weather for next week.

HYDROLOGY

Portions of the St Marys, Satilla, and tributaries to the St Johns River have risen into minor or moderate flood stage in response to widespread 4 to 8 inch rainfall over the portions of those basins over the last several days. Additional rainfall through the weekend may prolong or lead to other local river rises. Rain-free conditions next week will allow river levels to lower.

TIDES/COASTAL FLOODING

Coastal flooding will persist through the weekend within the St Johns River. Tides will be elevated along the Atlantic coast. Winds will strengthen through Friday and combine with the astronomical peak tides with the New Moon, yielding Minor to low-end Moderate flooding along at the beaches through at least Saturday night's high tide.

Due to widespread 4 to 8 inches of rainfall across the lower basin of the St Johns river, tidal levels will likely reach moderate levels again with the high tide, up to near 2.25 feet above normally dry ground. A Coastal Flood Warning remains in effect due to the combination of the freshwater runoff and ongoing 'reverse flow' with the middle and upper portions of the St Johns River. May be able to let the coastal flood warning expire at 5 PM this afternoon. Anticipate water levels at high tide to be at least at Minor Flood level through the weekend within the St Johns.

PRELIMINARY POINT TEMPS/POPS

AMG 68 75 69 80 / 10 60 90 100 SSI 74 82 74 83 / 40 80 100 90 JAX 71 82 72 86 / 60 90 90 90 SGJ 72 83 75 87 / 80 90 80 90 GNV 69 83 72 87 / 80 80 70 80 OCF 70 86 74 88 / 80 70 40 80

JAX WATCHES/WARNINGS/ADVISORIES

FL...Flood Watch until 3 AM EDT Friday for FLZ038-137-138-140-233- 237-240-333-340-433-533-633. High Risk for Rip Currents through late Saturday night for FLZ124- 125-138-233-333. Coastal Flood Advisory until 2 PM EDT Saturday for FLZ125-132- 137-225-325-633. GA...High Risk for Rip Currents through late Saturday night for GAZ154- 166. MARINE...Small Craft Advisory from 6 AM Friday to 2 AM EDT Sunday for AMZ450-470. Small Craft Advisory until 2 AM EDT Sunday for AMZ452-454-472- 474.