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

- Scattered to Numerous Thunderstorms through this Evening. Isolated Strong Storms with Wind Gusts of 40-50 mph, Frequent Lightning, and Torrential Downpours are Possible.

- Slow Moving Downpours will Increase the Threat For Localized Flooding, Especially at Urban and Normally Flood Prone Locations.

- High Risk of Rip Currents at Northeast FL Beaches this Afternoon. Moderate Risk at the Southeast GA Beaches.

- Isolated to Scattered Afternoon and Evening Thunderstorms from Monday through Saturday.

- Heat and Humidity Builds this Week. Heat Advisories Possible Each Day from Tuesday through Friday.

NEAR TERM /THROUGH TONIGHT/

Main Highlights:

- Scattered to Numerous Showers and Thunderstorms through this Evening.

- Isolated Strong Storms are Possible, with Wind Gusts of 40-50 mph, Frequent Lightning Strikes, and Heavy Downpours.

- Slow Moving Downpours will Increase the Threat For Localized Flooding, Especially at Urban and Normally Flood Prone Locations.

- Moderate to High Risk of Rip Currents at Area Beaches.

Afternoon surface analysis depicts a surface trough positioned along the Carolina coast that extends southwestward across southeast GA, while Atlantic high pressure (1023 millibars) was building westward across north central FL. Aloft...deep-layered Atlantic ridging was extending its axis westward across the FL peninsula and into the eastern Gulf. Latest GOES-East derived Total Precipitable Water imagery indicates that deep tropical moisture remains in place across all of southeast GA and northeast FL, where PWATs of 2.1 - 2.3 inches prevail. A slightly drier air mass associated with the Atlantic ridge axis has advected northward into north central FL, where PWATs ranged from 1.8 - 2 inches. Slow moving convection continues to expand and backbuild along the trough axis from the along the I-95 and U.S.-301 corridors in southeast GA, with isolated convection developing along the I-95 and I-10 corridors in northeast FL and the Suwannee Valley. A healthy cumulus field was otherwise building across our area, with temperatures at 18Z ranging from the lower 90s inland to the upper 80s at coastal locations, with dewpoints generally in the 70s inland and around 80 at coastal locations, creating heat index values mostly in the 100-105 degree range.

Given plenty of tropical moisture in place, we expect convection to gradually expand in coverage and intensity along the I-95 and U.S.- 301 corridors through mid-afternoon, with activity tending to backbuild along the lingering trough axis that extends into the Okefenokee Swamp in southeast GA. Convective outflows will push southward and should then collide with other mesoscale boundaries to develop scattered to numerous showers and thunderstorms into the early evening hours across the rest of northeast and north central FL. Colliding mesoscale boundaries should allow for at least a few storms to pulse and become strong, with wet microburst potential that could produce 40-50 mph winds, along with frequent lightning strikes and torrential downpours. Locations along the I-10 and U.S.- 301 corridors in northeast FL may have a slightly higher potential for stronger storms later this afternoon as mesoscale boundaries converge over these areas. Inland highs should reach the low and mid 90s at most locations, with heat index values peaking in the 103-107 degree range, or just below local Heat Advisory criteria. Coastal highs will reach the upper 80s to around 90 before the sea breeze pushes further inland.

Convective outflows may push convection towards the I-75 corridor in the Suwannee Valley and interior portions of north central FL early this evening, with activity then expected to dissipate before midnight. Debris cloudiness will thin out during the overnight and predawn hours, with the Atlantic ridge axis remaining in place across north central FL. This will create low level west- southwesterly flow that could advect low stratus cloud cover and fog northeastward from Apalachee Bay into the Suwannee Valley towards sunrise. Lows will fall to the mid 70s inland and the upper 70s to around 80 at coastal locations.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/

Main Highlights This Period:

- Daily Scattered Afternoon Thunderstorms.

- Increasing Heat Index Values near Heat Advisory levels each day. Lower precipitation chances will be present to start off the work week as mid-level ridging suppresses convection. Monday, rain/storm chances will be at about 20-40% for northeast Florida and the Georgia coast. Isolated to scattered afternoon and evening storms are forecast Tuesday across most of southeast Georgia, and closer to the northeast Florida coast. With less cloud cover and storm coverage, highs will be above normal, climbing into the lower to upper 90s. Max afternoon apparent temperatures will range from 100- 108 degrees, a Heat Advisory may be needed for some locations either or both days. Can't rule out some early morning patchy fog, especially over areas that receive a lot of rainfall.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

Main Highlights This Period:

- Isolated to Scattered Afternoon Thunderstorm Coverage.

- Heat Advisory Potential Each Day.

Storm chances remain lower than normal through the end of the week with precipitation chances generally maxing out around 40% each afternoon. Wednesday, convection will be limited to along and north of I-10 as well as down the northeast Florida coast. Isolated showers and storms expected inland Thursday, with slightly higher chances closer to the east coast. Precip chances increase Friday and Saturday area-wide but still peak in the 40-50% range.

Westerly surface winds will allow for hot temperatures each day, even at the immediate east coast beaches as the Atlantic sea breeze will be pinned from pushing inland. Max afternoon heat index values will approach Heat Advisory criteria near the coast and for some inland locations.

AVIATION /18Z SUNDAY THROUGH 18Z MONDAY/

Thunderstorms will gradually move away from the SSI terminal, with activity expected to move west of the terminal by 20Z. Convection will gradually develop near the Duval County terminals and SGJ through the mid-afternoon hours, with TEMPO groups for brief surface wind gusts up to 25 knots and IFR conditions placed in the TAFs through around 20Z at JAX and CRG, while activity may linger through around 00Z at VQQ. Thunderstorms will likely develop near the SGJ terminal towards 19Z, and a TEMPO group for brief surface wind gusts around 25 knots and MVFR conditions placed in the TAF through around 21Z. Activity should progress southward later this afternoon and evening, with potential impacts at GNV after 21Z. Confidence remains too low for a TEMPO group, but a PROB30 group for brief surface wind gusts up to 25 knots and MVFR conditions during heavier downpours was extended through around 01Z. Convection over northeast and north central FL should dissipate by 03Z, with VFR conditions then prevailing at all but the VQQ terminal overnight, where periods of MVFR to IFR conditions are expected after 06Z. VFR conditions should then prevail by 12Z.

MARINE

Weak troughing situated off the southeastern seaboard will continue to progress northeastward this afternoon, with Atlantic high pressure slowly building westward across our local waters tonight and Monday. Scattered thunderstorms will develop close to the near shore waters this afternoon hours. A few stronger storms will be possible, with briefly gusty winds, frequent lightning strikes, and torrential downpours through early this evening. Southwesterly flow will then prevail beginning on Monday, with an afternoon sea breeze developing over the near shore waters each afternoon, followed by a southerly evening wind surge. Winds and seas are forecast to remain below Caution levels this week. Only isolated afternoon and evening thunderstorms are forecast from Monday through Friday, mainly impacting the near shore waters.

Rip Currents: Breakers of 2-3 feet will combine with an easterly ocean swell and the outgoing tide to keep a high risk in place this afternoon at the northeast FL beaches. Lower surf heights at the southeast GA beaches will yield a moderate risk. Breakers will subside on Monday as prevailing winds become southwesterly, but the afternoon sea breeze will combine with a lingering ocean swell to produce a lower end moderate risk at area beaches during the afternoon hours. Persistent offshore winds will likely lower this risk by midweek.

FIRE WEATHER

- Patchy high afternoon dispersions beginning Tuesday.

Light west to southwest winds will keep the Atlantic seabreeze near the coast each day, with lower thunderstorm coverage expected Monday onward, precipitation chances will be around 20-40%. Temperatures will rise into the mid to upper 90s inland and low to mid 90s at the coast by Tuesday with peak heat index values rising to heat advisory levels 106-110 into midweek. Dispersions improve to the good range on Monday. Patchy high inland dispersions expected Tuesday into the end of next week as mixing heights increase under the ridge along with increasing westerly transport winds. Fog Potential: Significant fog development is not expected, with shallow, patchy fog late overnight limited to areas that receive locally heavy rainfall. A few strong thunderstorms may produce gusty outflows with locally erratic winds.

PRELIMINARY POINT TEMPS/POPS

AMG 75 95 75 95 / 40 20 10 20 SSI 78 92 79 95 / 20 20 0 20 JAX 75 94 75 95 / 30 30 0 20 SGJ 77 91 76 94 / 20 20 0 10 GNV 75 94 74 94 / 30 30 0 10 OCF 75 94 75 94 / 20 10 0 10

JAX WATCHES/WARNINGS/ADVISORIES

FL...High Risk for Rip Currents until 10 PM EDT this evening for FLZ124- 125-138-233-333. GA...None. MARINE...None.