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

- Areas of Locally Dense Fog Possible Early this Morning Across Inland Portions of Southeast GA, Possibly Extending into the Suwannee Valley.

- Isolated to Widely Scattered Thunderstorms this Afternoon and Evening. Localized Flood Potential at Inland Locations Due to Slow Storm Motion.

- Scattered to Numerous Showers and Thunderstorms Area-Wide on Wednesday.

- Strengthening North-Northeasterly Winds at Coastal Locations on Wednesday Night and Thursday, with Locally Heavy Downpours Possible Along the Northeast FL Coast.

- Increasing Marine and Coastal Impacts Expected on Thursday and Thursday Night and Friday. - Minor Coastal Flooding Likely Around Times of High Tide Along the Atlantic Coast from Thursday Evening through the Weekend. Tidal Flooding Possible within the St. Johns River Basin from Friday through the Weekend.

- Onshore Winds Gradually Diminish on Saturday Night and Sunday, with an Unseasonably Dry Air Mass Overspreading Our Area this Weekend and Early Next Week.

NEAR TERM /THROUGH TONIGHT/

Main Highlights:

- Isolated to Widely Scattered Thunderstorms expected this Afternoon and Evening.

- Localized Flood Potential Due to Slow Storm Motion Inland.

- Locally Dense Fog This Morning and Late Tonight.

Overall a similar or slightly less active day is expected today as compared to Monday, as weak surface troughing and high pressure ridging remain across the region. Northeasterly winds will bring a few isolated showers onshore once again this morning, with coverage expanding inward through the day as daytime heating ramps up. Isolated to widely scattered storms will be possible primarily in the afternoon and evening hours, especially for central and western portions of the area as the sea breeze moves inland. Once again, not a significant strong storm threat like Monday, as the weak upper troughing moves out of the area and overall instability lessens to a certain extent. Very high PWATs will result in mainly heavy rain/minor flooding being the primary hazard potential in addition to some gusty downbursts. Above average temperatures in the low 90s inland will continue, with coastal highs in the mid to upper 80s.

Northeasterly winds start to gradually surge overnight tonight as a frontal boundary approaches from the west, and low pressure starts to develop south of Cape Hatteras along the boundary, tightening the pressure gradient a bit. More significant impacts do not arrive until later on Wednesday, though overnight coastal shower potential increases from the northeast accordingly, especially for coastal GA. Lows will be mild and muggy again before the arrival of the front, mainly in the low to mid 70s. Less confident overall in the fog potential Wednesday Morning given more of a transition period, though at least some patchy fog will be possible inland once again, especially over interior north/central FL.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/

Main Highlights This Period:

- Scattered to Numerous Showers and Thunderstorms Area-Wide on Wednesday.

- Strengthening North-Northeasterly Winds at Coastal Locations on Wednesday Night and Thursday, with Locally Heavy Downpours Possible Along the Northeast FL Coast.

- Increasing Marine and Coastal Impacts Expected on Thursday and Thursday Night.

Troughing aloft will dig and sharpen over the eastern third of the nation as ridging amplifies over Texas, the Southern Plains, and the lower Mississippi Valley. Meanwhile, strong high pressure building over southeastern Canada and New England will push a "backdoor" cold front down the southeastern seaboard on Tuesday night and Wednesday, with this front crossing southeast GA on Wednesday and then slowing its southward progress over northeast and then north central FL on Wednesday night and Thursday. Deep tropical moisture will pool ahead of this "backdoor" cold front along the I-95 corridor and north central FL on Wednesday, with a drier air mass slowly filtering into interior southeast GA and the Suwannee Valley during the late afternoon and evening hours. Our local pressure gradient will tighten as the day progresses from north to south as high pressure wedges down the southeastern seaboard in the wake of the frontal boundary, while low pressure begins to deepen off the Mid-Atlantic coast. Convergent northeasterly low level flow and plenty of available moisture should develop numerous showers and a few embedded thunderstorms by the late morning hours across coastal southeast GA, with activity then expanding southwestward across much of northeast and north central FL during the early to mid afternoon hours. Locally heavy downpours will be possible, especially along the I-95 corridor in northeast FL, and breezy conditions at coastal locations will keep highs generally in the mid 80s. Inland highs should still climb to the upper 80s to around 90 before showers and thunderstorms increase in coverage.

A drier air mass will advect into our region on Wednesday evening from north to south, with PWATs falling below 1.5 inches across southeast GA before sunrise on Thursday. Meanwhile, our local pressure gradient will continue to tighten, and breezy north- northeasterly winds will prevail for locations along and east of I- 95 throughout the night. Convergent low level flow will continue to develop showers and a few embedded thunderstorms over the Atlantic waters overnight that will occasionally move onshore and impact areas along and east of I-95, with the drier air mass then shifting activity to coastal northeast FL by Thursday morning. Cool air advection will be countered by low stratus cloud cover in the wake of the frontal boundary, with lows falling to the upper 60s for inland southeast GA, with lower 70s elsewhere inland and mid to upper 70s for coastal northeast FL.

North-northeasterly winds will peak on Thursday at coastal locations, where sustained speeds of 20-25 mph will frequently gust to 35-40 mph. A Wind Advisory may be required for coastal locations on Thursday and Thursday evening. Bands of showers and isolated embedded thunderstorms developing near and just behind the southward moving frontal boundary could bring waves of downpours to coastal northeast FL and possibly north central FL, especially during the morning hours before the drier air mass over southeast GA and the Suwannee Valley overspreads the rest of our area by late Thursday afternoon and evening. Otherwise, plenty of low and mid level cloud cover and strengthening cool air advection will keep highs in the low to mid 80s, with upper 80s possible across north central FL, where the frontal passage may not occur until the afternoon hours.

A cooler and drier air mass will continue to funnel into our area on Thursday night as low level flow backs to a more northerly direction. Breezy to windy conditions will continue along the I-95 corridor and points eastward overnight, and a few coastal showers will remain possible, mainly for locations from around St. Augustine southward. Clearing skies and a light northerly breeze will drop lows to the lower 60s for most of inland southeast GA, and coastal locations in southeast GA will likely fall to the mid and upper 60s despite breezy conditions prevailing. Lows will drop to the mid 60s for the Suwannee Valley and I-10 corridor, while breezy to windy conditions keep lows in the low to mid 70s along the northeast FL coast.

LONG TERM /FRIDAY THROUGH MONDAY/

Main Highlights This Period:

- Marine and Coastal Impacts Continue on Friday and Saturday as Gusty Northeasterly Winds Prevail at Coastal Locations.

- Minor Coastal Flooding Likely Around Times of High Tide Along the Atlantic Coast from Thursday Evening through the Weekend. Tidal Flooding Possible within the St. Johns River Basin from Friday through the Weekend.

- Onshore Winds Gradually Diminish on Saturday Night and Sunday, with an Unseasonably Dry Air Mass Overspreading Our Area this Weekend and Early Next Week.

Troughing will continue to deepen along the U.S. Eastern seaboard on Friday and Saturday, allowing for low pressure to rapidly deepen off the Mid-Atlantic and New England coasts. This feature will likely retrograde towards these coasts on Saturday night and Sunday, with a deep and dry north-northwesterly flow in the wake of this strong coastal storm funneling an unseasonably dry air mass into our area this weekend and early next week.

Our local pressure gradient will remain tight on Friday, with breezy to windy conditions expected at coastal locations, where isolated showers will be possible on Friday morning for locations south of St. Augustine. Marine stratocumulus and cool air advection should keep coastal highs in the upper 70s to around 80. Breezy north- northeasterly winds will otherwise advect an unseasonably dry air mass into our area, allowing skies to clear from northwest to southeast and dewpoints to fall into the 50s across inland southeast GA by Friday afternoon, with values slowly falling through the 60s elsewhere. Highs at inland locations will generally reach the low to mid 80s, except upper 80s for locations south of Gainesville. Winds will then decouple on Friday evening at inland locations, allowing for radiational cooling overnight, possibly dropping lows to the mid to upper 50s for inland southeast GA, with low and mid 60s elsewhere inland and upper 60s to lower 70s at coastal locations, where breezy northerly winds will continue overnight.

Northeasterly winds will remain breezy on Saturday for locations along and east of I-95, but our local pressure gradient will loosen by Saturday night and Sunday, with additional nights of radiational cooling expected at inland locations. A rather pleasant early Autumn weekend is expected area-wide, with dry weather and only gradually warming temperatures expected early next week as broad troughing and a dry northwesterly flow aloft prevail across the southeastern states. Highs will generally climb to the low and mid 80s this weekend for most locations as mostly clear skies and an unseasonably dry air mass continues, with inland lows likely falling into the 50s, with upper 60s forecast at coastal locations. Temperatures may climb slightly on Monday, but dewpoints will remain in the 50s for inland southeast GA and the 60s elsewhere, keeping overall pleasant conditions in place, especially overnight.

AVIATION /06Z TUESDAY THROUGH 06Z WEDNESDAY/

Impacts through this morning will continue to be with respect to FG and low stratus potential, with all terminals expected to have at least some impacts. Continue to expected inland northeast FL airfields (VQQ and GNV) to have the highest impacts where IFR conditions are forecast. Uncertainty is overall more elevated closer to the coast. Coastal shower potential persists throughout this morning as well, though not forecasting any operational restrictions at this time. Thunderstorm potential is overall low today, and therefore have not included any mention at this time with most guidance suggesting probabilities of 10 percent or less. Trends will be monitored for future updates accordingly. Otherwise, no other significant impacts this afternoon through tonight before a frontal boundary approaches after the forecast period.

MARINE

A surface trough and an upper level disturbance will lift northeastward today, with lingering scattered showers and thunderstorms continuing over local waters. Wednesday into Wednesday night, strong high pressure well to the north will help push a backdoor cold front south through the area, allowing for another round of showers and thunderstorms, and a surge of northeast winds and building seas. Small Craft Advisory will be expected as a result from Wednesday night through Friday, with potential for Gale Force Wind Gusts from Thursday to early Friday morning. Breezy winds and elevated seas will slowly subside this weekend.

Rip Currents: Weaker onshore flow will result in a lower-end moderate risk today at all area beaches. Northeasterly winds will gradually strengthen on Wednesday afternoon, creating a higher end moderate risk at area beaches. This risk will likely become high from south to north Wednesday evening through late week as a stronger northerly wind surge arrives.

FIRE WEATHER

- ELEVATED NIGHTTIME DISPERSION VALUES WILL BE POSSIBLE AT COASTAL LOCATIONS ON WEDNESDAY NIGHT AND WILL BE LIKELY ON THURSDAY NIGHT.

Scattered showers and isolated thunderstorms are expected to develop this morning at coastal locations, with activity moving slowly inland during the afternoon hours. Scattered to numerous showers and thunderstorms are expected area-wide on Wednesday, with shower activity then shifting to coastal locations on Wednesday night and Thursday. East-northeasterly surface and transport winds will prevail today, with poor to fair daytime dispersion values forecast. Northeasterly transport winds will gradually strengthen on Wednesday, with breezy surface winds developing along the I-95 corridor during the mid to late morning hours. Increasing cloud cover and rain chances will keep dispersion values in the poor to fair range. North- northeasterly surface and transport winds will remain breezy at coastal locations on Wednesday night, possibly creating elevated nighttime dispersion values. North-northeasterly surface and transport winds will continue to strengthen on Thursday and Thursday night at coastal locations, with breezy conditions developing at inland locations on Thursday morning, creating good daytime dispersion values area-wide. Elevated nighttime dispersion values will then be likely at coastal locations on Thursday night, as breezy surface speeds continue.

Fog Potential...Areas of locally dense fog are expected during the early morning hours on Tuesday across inland portions of southeast Georgia, with patchy fog possible early this morning across the Suwannee Valley and inland portions of north central Florida.

TIDES/COASTAL FLOODING

Astronomical tides will be on the rise later this week due to the upcoming Full "Harvest" Moon that occurs on Saturday. A northeast wind surge will overspread coastal locations on Wednesday and especially late Wednesday night that will combine with these increasing astronomical tides to create minor coastal flooding along the Atlantic coast and eventually into the St. Johns River from Thursday evening through at least the upcoming weekend. Minor coastal flooding will be possible along the Atlantic coast beginning with the evening high tide on Thursday, where water levels of 1.5 - 2 feet above Mean Higher High Water (MHHW) are preliminarily forecast. Minor flooding will then likely expand to the St. Johns River basin by Friday and will then be possible around times of high tide through the weekend and possibly into next week , as rising astronomical tides beyond the date of the Full Moon result in a "trapped tide" situation.

PRELIMINARY POINT TEMPS/POPS

AMG 90 70 90 69 / 30 10 40 10 SSI 86 74 86 72 / 30 20 60 40 JAX 88 72 88 72 / 30 10 60 20 SGJ 87 75 86 75 / 30 20 50 40 GNV 90 71 90 71 / 30 10 60 0 OCF 91 73 91 73 / 30 10 60 10

JAX WATCHES/WARNINGS/ADVISORIES

FL...None. GA...None. MARINE...None.