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

- Locally Heavy Rain Today. Flooding Rainfall Risk Continues. Storm Coverage Increases this Afternoon & Evening

- Moderate Rip Current Risk Today & Tuesday

- Daily Afternoon & Evening Thunderstorms

UPDATE

Today's main concern will be the potential for flooding rainfall, particularly in NE FL.

A slowing frontal boundary appears to be just pushing into FL at this time while the parent upper shortwave trough gradually moves southeastward. The frontal feature is likely to stall out near I-10, perhaps south today but will broaden into a wider frontal zone through the afternoon. A focus for convection will develop along the shallow frontal convergence and along the an early, quick-moving Atlantic sea breeze. The primary change during this update to the forecast was a decrease in shower/t'storm potential across portions of SE GA especially NW of Waycross where drying NNW flow prevails. Meanwhile, likely chances 50-70% are still expected for most of NE FL today with exceptionally high precipitable water, measured at 2.47" this morning. Given the moisture in the column, lapse rates are relatively weak and should mitigate the potential of very strong or severe t'storms this afternoon. Generally expect activity to develop along the stalled front and sea breeze and move south- southwesterly through the early afternoon.

NEAR TERM /THROUGH TONIGHT/

Highlights Through Tonight:

- Unsettled Weather & Cooler Today

- Localized Flood Risk Continues

Cloudy and cooler today with waves of showers and storms as a surface front across the Carolinas early this morning settles farther south and extends across north FL or very near the GA-FL state line by this afternoon. The mid-level trough across the region will edge slightly farther south today with the axis across north Florida. This will bring slightly drier air (PWATs falling below 2 inches under northerly flow) across southeast GA into the afternoon while keeping richer moisture and stronger lift across northeast FL, near and south of the surface front. Higher rain chances this morning will focus across northeast FL and along the Atlantic coast where onshore, breezy northeast winds develop on the northern side of the surface front. Into the afternoon, rain chances expand east to west as diurnal instability increases and another vorticity max within the mid level trough pivots southward across north-central FL. Breezy northeast winds develop north of the front along the southeast GA coast this morning, then east-northeast winds expand southward through the afternoon as the surface front settles farther south of north Florida as high pressure strengthens northeast of the region. An inverted coastal trough begins to form tonight over the adjacent coastal waters, with elevated northeast winds along the coast tonight and a chance of coastal showers and isolated storms.

The main short-term weather hazard will continue to be localized flooding rainfall, especially along the coast and inland across northeast Florida near and south of the surface front this afternoon and into the evening. Rich, deep layer moisture with PWAT near the daily max today of 2.3 inches at JAX combined with weak steering flow near 5 kts will create slow moving showers and storms, that could train near the front and inland from the coast as onshore flow develops.

Leaned on the cooler side of temperatures today given lingering clouds and waves of rainfall with highs in the low/mid 80s for locations near and east of Interstate 95 and the St. Johns River basin to the mid/upper 80s farther inland. Some of the hourly guidance is trending about 3-5 deg cooler for many locations today, so adjustments may be needed depending on if cloud breaks occur later today. Tonight, lows will range in the 70s under elevated NE winds along the coast.

AVIATION /12Z MONDAY THROUGH 12Z TUESDAY/

Unsettled weather prevails through the period due to a passing disturbance and associated front. Morning flight restrictions due to scattered areas of low stratus will lift to MVFR then VFR through 14z as showers increase in coverage for coastal terminals. Northeasterly flow will shift surface winds to NNE to NE this morning as isolated TSRA begins to develop at the coast and then shift southwestward through the afternoon. SHRA potential will continue through the day but the primary period of TSRA will be 15z- 19z for the coastal terminals and 17z-20z at KGNV. Northeasterly flow may lead to periods of showers through the overnight hours along the I-95 corridor and coast, leading to periodic visibility reductions.

MARINE

A front stalls across north Florida today then shifts south of the waters tonight into Tuesday as high pressure strengthens to the northeast. A brief period of Small Craft Exercise Caution conditions is possible mainly over the Georgia waters Tuesday as a coastal trough develops offshore, then elevated combined seas may bring Small Craft Exercise Caution conditions to the outer waters on Wednesday as the coastal trough begins weaken. High pressure builds east of the local waters Thursday then extends across the Florida peninsula Friday into the weekend with a return of westerly winds and the afternoon east coast sea breeze.

Rip current risk increases from north to south today as onshore flow develops with moderate risk for all local beaches. By Tuesday, solid moderate to possibly high rip current due to stronger and more persistent ENE onshore winds. High risk likely for all local beaches by Wednesday with persistent onshore flow and elevated surf with breakers 3-5 ft.

FIRE WEATHER

- Low Dispersions Over Northeast Florida On Monday

A cold front is expected to shift southward across southeast Georgia Today. Low daytime dispersion expected this afternoon across north central FL, possibly Tuesday due to more cloudiness and elevated rain chances. Surface winds and transport winds will begin to transition to northeast to east behind the front Today. Elevated rain chances are expected again on Tuesday and Wednesday.

Fog Potential: Gusty and erratic winds will occur with thunderstorm activity. Patchy inland morning fog possible each day.

HYDROLOGY

Coastal water levels begin to increase next week with the approach of the New Moon on Sept 11th and breezy onshore easterly winds late Tonight through Wednesday, with the peak winds across the local waters and coast Tuesday. At this time, extended probabilistic guidance keeps water levels below action stage late Tuesday through Wednesday both along the local Atlantic coast and within the St. Johns River basin.

PRELIMINARY POINT TEMPS/POPS

AMG 88 72 87 72 / 40 20 60 20 SSI 86 76 86 77 / 50 60 70 60 JAX 87 74 87 74 / 60 40 60 20 SGJ 85 75 85 76 / 50 30 60 20 GNV 87 72 88 73 / 60 20 70 10 OCF 88 73 88 73 / 60 30 70 20

JAX WATCHES/WARNINGS/ADVISORIES

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