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 redevelop Tonight and continue through Saturday Night. High Rip Current Risk, Rough Surf, Elevated Tides and Beach Erosion. Minor to locally Moderate Tidal Flooding Continues for the St Johns River through

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

UPDATE

Only slight changes to the forecast today and tonight were to increase the rain chances based on radar and latest high resolution guidance. May need to also trim back the t-storm chances since the rest of today will largely be isentropic lift processes with weak instability given MLCAPE of less than 800-1000 J/kg. No changes to the temps with slight amendments to the winds and sky conditions.

NEAR TERM /THROUGH TONIGHT/

Main Highlights Today and Tonight:

- Coastal and Marine Impacts Continue, Including Coastal Flood Warning for Upstream St. Johns River

- Numerous showers across North Central FL decreasing in coverage northward Nearly stationary boundary remains draped just south of our region, and has been generally nudging further southward throughout the day today as high pressure ridging is trying to make more of a push from our north. Main impact today will be more of a presence of drier air across southeast GA and to a small extent over northeast FL, which can already be seen on satellite imagery with breaks in the persistent low clouds. With onshore flow continuing just north of the front, showers with occasional heavy rainfall and perhaps a few rumbles of thunder will continue across a large portion of the area today similar to yesterday. The main difference being the highest PoPs and potential for heavy rainfall/flooding will shift slightly southward with the front, with generally from Saint Augustine to Gainesville and areas south being the primary impact zone. Showers will be more isolated near the I-10 corridor today, which is good news for Duval County where some areas have received 4-8+ inches of rain over the past 24 hours.

Aside from rainfall and breezy onshore winds, the other primary impact continues to be coastal/marine/St. Johns River flooding, with Coastal Flood Advisories continuing for the entire coast and St. Johns River east of Downtown JAX to Mayport, where about 1-1.5 feet of water above normally dry ground is expected at times of high tide. South of the JAX area, opted to upgrade to a Coastal Flood Warning based on trends and other ground truth, as water levels near or just above 2 feet above normally dry ground is forecast, and has already occurred in a few areas. This threat is expected to continue through at least Thursday Morning's high tide. Rip current risk also continues to be high at all area beaches.

Drier air will only make it to about the FL/GA border tonight before a shift in the pattern is expected Thursday onward (more on that below), which will also suppress coastal showers just a bit overnight. Chances will mainly be confined to similar areas as during the day today, but overall around 10-20% less.

With breaks in the sun today, especially across southeast GA, these areas will see temps a few degrees higher than average. Generally looking at low 80s over inland GA and the upper Suwannee Valley area, and mid 70s to around 80 elsewhere.

SHORT TERM /FRIDAY THROUGH SUNDAY 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 /MONDAY THROUGH WEDNESDAY/

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 /12Z THURSDAY THROUGH 12Z FRIDAY/

Some areas of low cigs down to IFR inland at GNV and VQQ will be possible, but at this time looks pretty intermittent through about 15z. Otherwise, a risk of MVFR cigs for all the TAFs through 16z- 17z. and then mostly VFR cigs prevail. While there may be prevailing VFR cigs later today, there is a good chance of rain and light showers but vis generally expected to be either MVFR or VFR. Will probably have PROB30 or TEMPO groups in for northeast FL TAFs for this possibility. Later tonight, probably looking at increasing chances of low cigs again with highest chance of MVFR especially GNV, SGJ, VQQ, and CRG, and can't rule out IFR after 05z/06z. Areas of rain and scattered showers will also be increasing gradually overnight. For Sfc winds, mainly northeast increasing up to 10-15 kt today and gradually turning more east after 00z while decreasing to 5-10 kt.

MARINE

East northeast winds and seas with small craft caution conditions for the most of most of the waters by later today and this evening. 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 Friday through Saturday.

The National Hurricane Center is monitoring Hurricane Isaias in the southwestern 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 northeasterly wind surge persisting along the Georgia and northeast FL coast through today will result in strong rip currents and rough surf. High Risk for Rip Currents will likely continue through this weekend with continued breezy onshore flow.

FIRE WEATHER

- Low Dispersions Across North Central Fl Today

A brief break in the rain today for most areas, followed by a return to soggy conditions Friday and increasing thunderstorm chances over the weekend as a warm front lifts across the region. Direct local impacts from Hurricane Isaias are not expected but fringe outer rain bands may reach portions of the Suwannee Valley Friday night into Saturday. Conditions will dry out and warm up next week as drier air pushes in behind the remnants of Hurricane Isaias. No immediate fire weather concerns or weather watch outs over the weekend.

FOG POTENTIAL AND OTHER WEATHER REMARKS: Dense fog formation is not expected over the next few days. Heavy rainfall may lead to another potential period of flash flooding Friday and Saturday. Isolated severe thunderstorms will be possible Friday night through Saturday with risk of isolated tornadoes.

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 this morning but will lower as winds continue to decrease this afternoon. 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 morning high tide, up to 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. Will reassess the need to extend the Coastal Flood Warning later this morning after high tide. 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 82 68 77 69 / 0 10 50 80 SSI 83 73 82 74 / 30 30 60 90 JAX 82 71 81 72 / 40 40 70 90 SGJ 81 73 82 74 / 70 60 90 90 GNV 80 69 81 71 / 80 60 90 60 OCF 79 70 83 73 / 80 70 80 40

JAX WATCHES/WARNINGS/ADVISORIES

FL...Coastal Flood Advisory until 5 PM EDT this afternoon for FLZ124-138-233-333. High Risk for Rip Currents through late Saturday night for FLZ124- 125-138-233-333. Coastal Flood Advisory until 2 PM EDT Saturday for FLZ125-225. Coastal Flood Warning until 5 PM EDT this afternoon for FLZ132- 137-325-633. Coastal Flood Advisory from 5 PM this afternoon to 2 PM EDT Saturday for FLZ132-137-325-633. GA...Coastal Flood Advisory until 5 PM EDT this afternoon for GAZ154-166. High Risk for Rip Currents through late Saturday night for GAZ154- 166. MARINE...Small Craft Advisory from 8 AM Friday to 2 AM EDT Sunday for AMZ450-470. Small Craft Advisory from midnight tonight to 2 AM EDT Sunday for AMZ452-454-472-474.