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

- Peak Heat Index Today 105-110 this Afternoon & Evening. Heat Advisory Northeast Florida & Portions of Southeast Georgia

- Scattered Thunderstorms Originating along the Coastal Sea breeze will shift Inland into Evening. Strong storms capable of locally gusty winds.

- Moderate Rip Current Risk Northeast FL Beaches Today. Increasing Risk Tuesday and Wednesday.

- Minor River Flooding for Satilla River

NEAR TERM /THROUGH TONIGHT/

Main Highlights Today and Tonight:

- Heat Advisory for NE FL and eastern areas of SE GA through 7 PM

- Isolated strong storm potential north-central FL this evening

Weak prefrontal troughing that slid through the region overnight has since stalled across central FL this afternoon. Northwesterly flow behind that trough has slowed the Atlantic sea breeze development so far this afternoon but with additional heating a late afternoon push is expected.

The strong heating beneath robust upper ridge centered to the northwest has bolstered temperatures into the low and mid 90s early this afternoon with highs forecast to reach the mid and upper 90s in a few hours. Heat index values have already risen into the 100s and is expected to peak around 3-5 PM in the 104-110 range for most areas, especially near the coast. A Heat Advisory remains in effect through 7 PM this evening.

With regards to convection, the tug of war between the "ridge rider" enhancement and the large upper ridge suppression - the ridge appears to be winning. Upper air observations this morning indicated fairly warm mid levels and several pockets of dry air above 850 mb, which will act to mitigate t'storm coverage this afternoon. HiRes convective models have caught up some and have indicated more isolated to widely scattered convection through the afternoon with the latest runs. If a strong enough updraft, the aforementioned dry pockets aloft will support the potential for isolated strong to marginally severe wet microbursts capable of gusts up to 60 mph. North-central FL areas will have the highest threat for deeper, stronger convection later this afternoon as the Gulf sea breeze begins to interact with outflow.

For this evening there could be lingering convection across inland NE FL as outflows interact through around 10 PM. The "backdoor" cool front pushes in from the NE this evening. Some of the showers and isolated storms could hang on along the front as it pushes into SE GA late this evening. Some mid cloud cover will push southwestward but overall skies will begin to clear and allow inland temperatures to cool to the mid 70s while onshore flow will keep conditions warmer in the upper 80s to around 80.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/

Tuesday & Wednesday...

Main Highlights This Period:

- Breezy East Winds & Elevated Rip Current Risk - Inland Strong Afternoon & Evening Storms

A transition to a stronger east coast sea breeze regime and drier conditions across southeast GA with the position of the 1000-500 mb ridge centered across TN/KY. This pattern will bring a chance of a a few spotty morning showers and early afternoon thunderstorms along the dominant east coast sea breeze as it shifts inland, with convection blossoming into the afternoon and evening across inland areas. Sea breeze and outflow boundary mergers will focus toward the I-75 corridor and westward each afternoon and into the evening.

The highest rain chances focus across inland NE FL each day where deeper moisture lingers. Tuesday, a frontal zone combined with sea breeze forcing across inland northeast FL favors higher than climo rain chances, especially for locations west of Highway 301 toward the Interstate 75 corridor during the afternoon and evening. Below average precipitable water and mid/upper level subsidence across southeast GA invades Tuesday afternoon into Tuesday evening brining below average rain chances. Wednesday, the drier airmass continues to linger across locations generally near and north of the Interstate 10 corridor with a continuation of mostly dry weather across southeast GA with the higher daily shower and thunderstorm rain chances southward across inland north-central FL in the afternoon and evening. For all locales, Wednesday is trending drier than Tuesday with more abundant mid and upper level dry air in place.

With the pattern shift of onshore, easterly winds, high temperatures will top out near 90 at the beaches and rise into the mid to upper 90s inland. With the drier air, dew pts mixing down into the low 70s to evening mid/upper 60s across parts of southeast GA will bring lower peak heat index values compared to recent days, generally in the 100-105 degF range, below local Heat Advisory criteria.

LONG TERM /THURSDAY THROUGH SUNDAY/

Thursday through Sunday...

Main Highlights This Period:

- Higher Rain Chances Return for Northeast FL - Building Heat for Southeast GA

Thu & Fri...The mean layer 1000-500 mb ridge dominates north to northeast of the region as a broad upper level low/trough approaches Florida from the east. This pattern will bring a continued easterly steering flow and a more dominant Atlantic/east coast sea breeze regime. Moisture and thus rain chances will be higher across northeast FL with the approaching upper level feature, and rainfall may not follow a typical sea breeze regime given upper level forcing and more abundant cloud cover with the passing upper level trough. Warmer temperatures and drier weather continues across southeast GA closer to the influence of the upper level ridge. Heat index values Friday near local Heat Advisory criteria (108-112 degF) across parts of NE FL.

Sat & Sun...The upper level trough feature drifts farther westward while the upper ridge rebuilds and strengthens east to southeast of the southeast coast. This will transition prevailing winds from SSE to SSW into early next week, with deeper moisture expanding back northward across southeast GA. Local rain chances increase across all areas this weekend with active sea breezes brining afternoon and evening storms. For Independence Day, at this time, looks like the higher chances of thunderstorms will focus across northeast Florida during the afternoon, and then interior northeast FL during the evening with very weak storm motion...meaning that the rain and lightning threat could linger for a longer period of time where evening storms do form. A warming trend ensues into the weekend as well with highs pushing back into the mid to upper 90s with daily heat index values 105 deg, near but just shy of local heat advisory criteria.

Tropical Outlook: There is a very low 10% chance of a low gaining tropical characteristics along a front offshore of the southeast Atlantic coast through mid-week. Later in the week, conditions become more unfavorable for development. There are no significant local impacts associated with this feature.

AVIATION /18Z MONDAY THROUGH 18Z TUESDAY/

The Atlantic sea breeze is pushing inland into the coast but will slow to move inland against the northwesterly winds. Widely scattered showers and thunderstorms are expected to initiate along the sea breeze and gradually shift inland from I-95 toward inland terminals during the late afternoon and early evening. The best chances for TSRA continues to be KGNV around 22z-02z but a shrinking chance still exists at airfields along the I-95 corridor through the afternoon hours. Main concern will be strong, gusty outflow up to 35 knots with passing and VCTS. Activity may linger at KSSI through 04z as a backdoor front pushes into the airfield, shifting winds northeasterly as it does so. Otherwise, VFR conditions are likely elsewhere through the overnight hours. Northeasterly winds prevail Tuesday with chances for PM convection focused along and west of I- 75.

MARINE

While the sea breeze remains over the water, a few showers or an isolated storm is possible a few miles from the shoreline. A backdoor front will push into the waters this evening, shifting prevailing wind to northeasterly Tuesday and Wednesday. The onshore flow will keep thunderstorm activity well inland through the middle of the week. The front will settle south of the waters through Saturday before it lifts back northward into the area as remnant inverted trough Thursday resulting in an increase in rain and storm chances. As surface high pressure builds to the south, a weak southwesterly flow will develop into the Independence Day holiday weekend and increase chances for thunderstorms.

Rip Currents:

Low-end Moderate Risk this afternoon with the development and inland push of the sea breeze. Persistent and breezy northeasterly winds on Tuesday should yield a solid moderate risk at all area beaches, with a potential high risk on Wednesday as surf builds to 3 to 5 feet.

FIRE WEATHER

- Daily Localized High Dispersion North Of Interstate 10

Easterly winds prevail Tuesday and Wednesday, with increasing speeds into the afternoon at the coast inland toward the St. Johns River basin trailing the east coast sea breeze passage. Gusts near 25 mph possible. Morning showers and isolated early afternoon coastal storms Tuesday will shift inland toward the Highway 301 and Interstate 75 corridor into the afternoon where isolated stronger storms are possible through the early evening. Drier conditions will prevail across southeast GA. Wednesday, mostly dry weather prevails north of Interstate 10 including across the Okefenokee NWR and Osceola NF. The higher thunderstorm chances will be across north- central FL Wednesday afternoon and evening, including near the Ocala NF. Minimum humidity will remain above critical values. FOG POTENTIAL AND OTHER REMARKS: Significant fog is not expected during the next several days. Stronger storms will be capable of producing strong and erratic wind gusts, along with frequent lightning strikes and heavy downpours, especially on Tuesday afternoon and evening across inland northeast Florida.

HYDROLOGY

Minor flooding continues along lower portions of the Satilla River Basin, as water levels have crested in minor flood stage at the gauge near Atkinson. Minor flooding will continue during the next several days.

PRELIMINARY POINT TEMPS/POPS

AMG 96 76 94 73 / 20 30 30 10 SSI 93 80 89 80 / 40 30 10 10 JAX 97 78 93 76 / 40 40 20 20 SGJ 95 77 91 78 / 30 30 20 20 GNV 97 76 94 74 / 30 40 70 10 OCF 96 77 93 75 / 40 30 90 20

JAX WATCHES/WARNINGS/ADVISORIES

FL...Heat Advisory until 7 PM EDT this evening for FLZ021-023-024- 030-031-035-038-120-124-125-132-136>138-140-220-225-232- 233-236-237-240-322-325-333-340-422-425-433-522-533-633. GA...Heat Advisory until 7 PM EDT this evening for GAZ136-152>154- 162-163-165-166-264-350-364. MARINE...None.