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

- Moderate Rip Current Risk all Local Beaches Today and Friday. Likely High Risk Returning by Tuesday Next Week

- Daily Heat Index up to 107 through Sunday

- Daily Afternoon & Evening Thunderstorms. Main Hazards: Locally Heavy Rain, Lightning & Gusty Winds Up to 40-50 mph

- Gusty coastal conditions and small craft advisory conditions developing Tuesday through Thursday next week

NEAR TERM /THROUGH TONIGHT/

Main Highlights:

- Potential for isolated strong thunderstorms and localized flooding

- Summertime heat continues with heat index peaking in low 100s

Persistent and deep southwesterly flow prevails this afternoon and overnight between a dominant ridge and in incoming shortwave. The incoming disturbance will graze the region through tonight into Sunday morning as it deflects eastward off the stubborn ridge. A Gulf moisture tap, continues to stream a "premium grade" of deep moisture-laiden air across the area this afternoon. The same southwesterly flow delivering the moisture has already promoted early afternoon convection across the Suwannee Valley, which will continue to move east-northeastward around 15 mph while scattered showers will develop as diurnal instability increases through the mid to late afternoon. Convective trends through the rest of the afternoon will follow closely to what played out yesterday with stronger convection developing along the collision of mixed bag of boundary collisions consisting of the pinned Atlantic sea breeze, Gulf Breeze, St Johns River breeze, and amalgamating outflows.

Highest concern with activity today will be the potential for concentrated flooding, mainly due to heavy rainfall rates that could push 4-5" per hour. Flood vulnerable areas will be those that are in poor drainage (urban) areas, low-lying, and at sites that received heavy rainfall within the last 24 hours. The I-95 corridor will be the main focus for the heavy rain/flood threat this afternoon where a 3-hr rainfall total greater than 1" is 70% and 3"+ at 30% for the NE FL portion of I-95. Despite the decent storm motion, the possibility of backbuilding will be possible along strong easterly outflows which may amplify flooding concerns. Additionally, enhance convergence along mesoscale boundary collisions may intensify updrafts producing strong thunderstorms capable of excessive lightning and strong outflow up to 50 mph due to water-loaded downdrafts.

Most of the convective allowing solutions depict weakening convection toward sunset this evening with potential for re-invigoration along leftover outflow as the aforementioned shortwave edges closer this evening. Divergence associated with this feature will be more likely to support evening convection through around midnight for portions of SE GA, mainly north of Waycross but cannot rule out a few attempts of as far south as I-10. After midnight activity will wind down and begin a recharge for another bout of convection Sunday.

Summertime heat continues under the influence of the upper ridge and will push readings into the low 90s through the rest of the afternoon and heat index into the low 100s. Under partly cloudy skies tonight temperatures will gradually cool to the low to mid 70s.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/

Main Highlights This Period: (Sunday through Monday night)

- Daily Thunderstorm Potential Sunday and Monday, with a few strong storms possible, with gusty winds and heavy rainfall

A trough of low pressure will extend south across the southeastern US Sunday, with a high pressure ridge centered to the southeast extending across south FL. Between these features, the low level flow will from the southwest. The flow will be light enough for the east coast sea breeze to move inland to around I95. Convection will start inland Sunday late morning to early afternoon, then work east through the afternoon. The greatest chance for storms will be along the I95 corridor due to sea breeze interactions.

The trough will dissipate Monday, as high pressure builds to the north northeast. The flow will remain light Monday, but will come more from the northeast to east. This will allow the east coast sea breeze to push well inland, so the convective max in the afternoon will be more toward the central part of the forecast area. Some drier will filter south into SE GA Monday, so higher convective chances expected for NE FL, than SE GA.

Temperatures this period will remain above seasonal averages.

LONG TERM /TUESDAY THROUGH FRIDAY/

Main Highlights This Period Tuesday through Saturday:

- Daily Thunderstorms Potential

- Elevated Rip Current Risk

Strong high pressure will build to the north northeast Tuesday through Wednesday night, an inverted trough develops just east of the region. The gradient between these two features will be pinched, leading to an elevated northeast flow. Tuesday and Wednesday will be gusty days along the coast, and across NE FL. Convection potential these two days will be greatest near the coastal trough, due to subsidence from the high.

Inverted troughing will settle overhead Thursday through Saturday. Daily thunderstorm potential will continue due to diurnal heating and convergence associated with this trough.

Near seasonal temperatures are forecast for this period.

AVIATION /18Z SATURDAY THROUGH 18Z SUNDAY/

Confidence in TSRA impacts remains high with TEMPO for all terminals between 18z-24z. Non-thunderstorm winds will be light southwest to west, with east coast sea breeze developing at SGJ and SSI now, 18z. Thunderstorm wind gusts up to 35 knots cannot be ruled out but hail is unlikely to develop with any strong thunderstorms that develop. Temporary visibility restrictions to IFR and possibly lower are expected due to torrential rainfall. Activity will diminish but lingering showers may continue through 00z before completely dissipating by 02-03z. There's a low chance that additional showers develop at SSI late this evening.

Low stratus development and patchy fog may occur, especially inland during the predawn hours Sunday, mainly for VQQ and GNV; IFR stratus is possible. Winds will shift west-northwesterly on Sunday with most of the thunderstorm activity focusing across NE FL during the mid afternoon.

MARINE

Weakening high pressure south of the area will maintain south to southwest winds and afternoon sea breezes through the rest of the weekend. Daily mid to late afternoon thunderstorms will move offshore, bringing locally strong wind gusts and frequent lightning at times. On Tuesday, a cold front will push south, sending a strong northeasterly wind surge through the local waters and elevating seas. Small craft advisory conditions are probable for the coastal waters starting Tuesday and may continue into Wednesday and possibly Thursday.

Rip Currents: Prevailing offshore winds (except for an afternoon sea breeze) and weak easterly swells will keep a low-end moderate risk of rip currents in effect the next couple of days. Strengthening northeast winds late Monday night into Tuesday will likely result in a high risk at all area beaches through at least Thursday as breakers build.

FIRE WEATHER

A trough of low pressure will stretch across the southeastern US this weekend. High pressure will build to the northeast early next week, and strengthen through mid week. As this high builds, an inverted trough will develop east of the area. The gradient between these two features will result in elevated winds Tuesday through Thursday, especially at the coast. An inverted trough will settle overhead late in the week into the weekend. Daily thunderstorm chances are forecast, mainly in the afternoon and evening hours.

HYDROLOGY

As far as rainfall today into tonight, areal amounts of around 0.2 to 0.5 inches are forecast. Many areas may see less than that. However, model guidance shows some amounts of about 3 inches are possible in a few pockets mainly over the eastern zones, but also shown to be possible toward Alachua and Marion counties. As such, where these heavy rains occur today, temporary flooding is possible, especially in any poor drainage or urbanized areas.

PRELIMINARY POINT TEMPS/POPS

AMG 91 73 92 73 / 60 40 10 10 SSI 89 77 91 77 / 70 30 20 10 JAX 91 74 92 75 / 80 40 40 10 SGJ 90 75 91 76 / 60 30 40 20 GNV 91 73 92 74 / 60 20 30 20 OCF 92 74 92 75 / 60 20 50 10

JAX WATCHES/WARNINGS/ADVISORIES

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