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 Thunderstorms this Afternoon through Early this Evening. Isolated Strong Storms are Possible, with Wind Gusts of 40-50 mph and Frequent Lightning Strikes. Heavy Downpours May Cause Localized Flooding.

- High Risk of Rip Currents at northeast FL Beaches Today, Moderate Risk at the Southeast GA Beaches.

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

- Only Isolated to Widely Scattered Afternoon and Evening Thunderstorms are Forecast from Monday through Saturday.

NEAR TERM /THROUGH TONIGHT/

Main Highlights:

- Isolated Strong Storms and Localized Flooding are Possible this Afternoon and Evening.

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

For today, the pattern will feature a weak trough of low pressure north of the area while mid level ridging from the Atlantic builds in across central FL and nudges into our area this afternoon. Mean layer flow is south-southwest about 5 to 10 kt and PWAT imagery and guidance show values of about 1.9 to 2.3 inches today. Overall, the moisture levels are decreased compared to yesterday. Plentiful low level moisture is available and we have noted low level mean mixing ratios are very high at about 18 g/kg on forecast model soundings. Expect the Atlantic and Gulf sea breezes to penetrate inland and eventually merge between Interstates 75 and 95. The combination of high moisture, strong diurnal heating, and sea breeze/outflow interactions will support scattered thunderstorms, and may become numerous over a couple of inland counties, during the afternoon and early evening. POPs are generally shown at 30-55 percent today. A few storms could become strong, producing around 50 mph wet downburst winds, frequent lightning, and locally heavy rainfall. Localized heavy rainfall of about 3+ inches is possible. The WPC shows a marginal excessive rainfall risk for the inland areas later today which looks reasonable but the risk does not look as high was it was on Saturday based on guidance. Convective activity will diminish after sunset. Highs will range from the lower to mid 90s inland to near 90 degrees along the coast, with peak afternoon heat indices of 103-107 degrees. Overnight lows will be in the mid to upper 70s.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/

Main Highlights This Period:

- Only Isolated to Widely Scattered Afternoon and Evening Thunderstorms.

- Increasing Heat Index Values Each Afternoon, with Values Near Heat Advisory Levels on Tuesday. Monday, the mean 500 mb ridge over the western Atlantic will move to the southwest, near the east central FL coastal waters. Weak low level southwesterly flow around the surface ridge axis extending from the Atlantic into north central FL will limit the progress of the Atlantic seabreeze much past I-95. Slightly drier air will drift over the area under the high and with near seasonal PWATs of 1.7-1.9 inches. The drier air and lack of shortwave energy aloft will limit coverage of T'storms as strong diurnal heating and surface lift and convergence along the Gulf seabreeze surface with isolated T'storms as the Gulf seabreeze moves east across NE FL before more widely scattered T'storms developing near I-95 as it merges with the Atlantic seabreeze. A few storms could be briefly strong with wind gusts to around 40 mph.

Highs will rise Monday with low to mid 90s along and west of I-95 and around 90 at the immediate coast. Peak heat index values will be around 104-108 for most locations with isolated values of 106 to 110.

Monday night, convection will end after sunset with mostly clear skies by midnight under thin high level cirrus clouds. Light southerly winds will turn calm inland and 5-10 mph along the coast. Lows will be slightly above average in the low/mid 70s inland and along the upper 70s.

Tuesday, mid level ridging aloft will be centered near the NE Gulf waters and stretch across the central FL peninsula. Subsidence underneath the ridge will suppress afternoon convection with only isolated T'storms near the I-95 and US-17 corridors of NE FL and along and east of highway 301 in SE GA. The WSW winds 5-10 mph will prevail with the beaches turning southeasterly 8-12 mph behind the Atlantic seabreeze as it moves onshore and helps to kick of the limited afternoon convection.

Highs on Tuesday will rise to the mid/upper 90s away from the coast with low 90s along the beaches. The hotter coastal highs will raise peak heat index values into heat advisory levels 106-110 as dewpoints remain muggy in the mid 70s inland and the upper 70s at the coast.

LONG TERM /WEDNESDAY THROUGH SATURDAY/

Main Highlights This Period:

- Limited Afternoon Thunderstorm Coverage.

- Heat Advisory Potential Each Day.

The 500mb ridge will remain near the area positioned from the FL panhandle coast into central FL. A couple of fast moving mid level shortwaves will cross the deep south into the coastal SE Wednesday through Friday with more uncertainty into next weekend on whether the ridge will shift away to the NW as a stronger shortwave trough moves from the Mid Atlantic to the Carolina coast. The surface high pressure ridge axis will shift into south FL Wednesday into Thursday with a slight increase in the westerly flow over the area. The Atlantic seabreeze will remain offshore through the week and this will allow the coast will heat up to the low to mid 90s with mid 90s along I-95 and mid to upper 90s inland. Lows will be in the low/mid 70s inland and the mid/upper 70s along the coast in the light offshore flow.

Widely isolated thunderstorms expected across SE GA while staying dry over NE FL Wednesday and Thursday. Coverage will increase slightly over SE GA Friday into Saturday with widely scattered thunderstorms and isolated thunderstorms over NE FL.

Daily peak index values of around 110 are expected.

AVIATION /12Z SUNDAY THROUGH 12Z MONDAY/

IFR conditions will prevail at VQQ and GNV through around 13Z, with visibilities likely improving to MVFR by 14Z. VFR conditions are otherwise expected through around 15Z. Low MVFR ceilings of 1,000 - 2,000 feet are then forecast to overspread the regional terminals after 15Z, with prevailing MVFR ceilings expected through around 18Z. Showers and thunderstorms will then develop along inland moving sea, river, and lake breezes this afternoon, with confidence high enough to include TEMPO groups for briefly gusty surface winds and MVFR to IFR conditions during heavier downpours at SSI, the Duval County terminals, and SGJ, mainly after 18Z. Confidence remains a little too low for TEMPO groups at GNV, where a PROB30 group for briefly gusty surface winds and MVFR conditions during heavier downpours was maintained. Convection is expected to push south and east of the regional terminals towards 00Z. IFR conditions will likely develop at VQQ after 04Z Monday. Southerly surface winds will increase to 5-10 knots at the regional terminals by 15Z, followed by the Atlantic sea breeze boundary pushing inland after 17Z, resulting in surface winds shifting to southeasterly around 10 knots at SGJ and SSI before 18Z. Southeast to southerly surface winds of 5-10 knots will resume once convection moves away from the terminals towards 00Z, with diminishing speeds expected overnight at the inland terminals.

MARINE

Atlantic high pressure will slowly build westward across the area waters today through Monday, then push south into central Florida by Tuesday and Wednesday as troughing develops over the southeast states. Coverage of showers and thunderstorms will gradually decrease across our local waters through Monday, with unseasonably dry conditions then forecast for Tuesday and Wednesday as west to southwest winds prevail.

Rip Currents: Latest buoys show about 3 ft seas and dominate wave period of 8/9 seconds from the east. While ordinarily not huge concern, we had rips yesterday, more rough surf, and likely development of rip channels so opted to raise another high risk for today for the northeast FL beaches and will have moderate risk for southeast GA beaches. In addition, low tide is about 11AM to noon which heightens the risk. Supporting guidance from the NWPS model show probabilities of 70-90 percent today.

Breakers will continue to subside early next week as prevailing winds become southwesterly, with a lower risk forecast.

FIRE WEATHER

- Patchy high afternoon dispersions beginning Tuesday.

Today, a trough will lift away to the northeast with light south winds and scattered thunderstorms as Atlantic seabreeze moves to US- 17 and merges with the Gulf seabreeze near highway 301 with light southeast winds 5-10 mph behind the Atlantic seabreeze passage with gusts 15-20 mph at the coast turning light southwesterly 5-10 mph behind the Gulf seabreeze. High pressure ridging will be over the FL peninsula next week as a trough extends over the southeast states northwest of the area with decreasing thunderstorm coverage in the afternoon and light west to southwest winds keeping the Atlantic seabreeze near the coast each day. 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.

Daytime dispersions will be in the fair range inland today, but poor along the immediate coast where mixing heights will be lower. 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 93 74 95 75 / 40 30 20 10 SSI 90 78 92 79 / 30 10 20 0 JAX 92 75 94 75 / 50 20 30 0 SGJ 90 75 91 76 / 30 10 20 0 GNV 93 74 94 74 / 40 20 30 0 OCF 93 75 94 75 / 30 20 10 0

JAX WATCHES/WARNINGS/ADVISORIES

FL...High Risk for Rip Currents through this evening for FLZ124-125-138- 233-333. GA...None. MARINE...None.