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

- Isolated Strong storms with Gusts 40-50 mph Possible & Frequent lightning. Heavy Downpours May Cause Localized Flooding. Decreasing storm coverage Monday into next week

- Moderate to High Risk of Rip Currents at Area Beaches Today, and Moderate risk Monday through Tuesday

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

NEAR TERM /TODAY THROUGH TONIGHT/

Main Highlights:

- Isolated Strong Storms and Localized Flooding Possible

- Moderate to High Risk of Rip Currents at Area Beaches

Multilayered clouds are over the area at 2 AM, with light winds and some patchy fog and low stratus clouds. A few showers are noted over the coastal waters, pushing northward in the mean steering flow from the south at about 10 kt. An isolated shower remains possible from near Mayport northward to St Simons Island the next few hours.

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 mainly 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:

- Daily Afternoon Thunderstorms

- Increasing Heat Index Values near Heat Advisory levels each day 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 Returns 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 /06Z SUNDAY THROUGH 06Z MONDAY/

Areas of MVFR to IFR cigs expected over the next few hours at the Duval county TAF sites, and possibly for GNV, before scattering out and lifting by about 12z. VQQ site is showing LIFR conditions, which may last for a few hours.

There is plenty of moisture, especially in the lower levels, for a scattered to broken cumulus field that may produce periods of MVFR cigs from 13z to 17z. May see a couple of showers form from 16z to 18z, with additional scattered to possibly numerous showers and storms after 18z. Won't be as much coverage as Saturday, but chance enough to have PROB30 TSRA groups. May need to have TEMPO groups for JAX and VQQ if confidence increases.

Light southerly winds expected after 12z, and will turn southeast behind the Atlantic seabreeze 8-10 knots in the afternoon along the coast and 5-8 knots at VQQ with light southerly winds at GNV around 5-8 knots.

MARINE

Atlantic high pressure will slowly build westward across the area waters today through Monday, then pushing 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 / 30 30 20 10 SSI 90 78 92 79 / 30 10 20 0 JAX 92 75 94 75 / 40 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.