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

- Heat and Humidity Builds this Week through the Weekend. Heat Advisory For Parts of the Area Today. Heat Advisories Possible Each Afternoon and Evening from Wednesday through Sunday

- Widely Scattered Afternoon & Evening TStorms Today- Thursday. A Few Strong Storms Are Possible Across Portions of Southeast GA this afternoon

- Scattered Afternoon & Evening TStorms Friday - Sunday

NEAR TERM /TODAY THROUGH TONIGHT/

Main Highlights:

- Heat Advisory in effect from Noon to 7PM

- Scattered Thunderstorms This Afternoon and Early Evening, more numerous along the Southeast Georgia coast

- Brief Strong Storms Possible, Wind Gusts up to 40-50 mph, frequent lightning, and locally heavy downpours

- Moderate Risk of Rip Currents at Northeast Florida Beaches

Light southerly winds along the coast less than 10 mph are trending calm inland under some remaining high level clouds. The clouds will thin out over the next few hours with mostly clear skies into sunrise as winds turn southwesterly along the coast. Temperatures in the mid 70s inland and upper 70s to low 80s along the coast will only cool another couple of degrees until dawn. Only very localized shallow ground fog expected the rest of the early morning.

Today, 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 for much of inland areas along with PWATs under 2.0 inches, while northern and coastal portions of SE GA, thanks to PWATS elevating to 2.0 to 2.25 inches, will see scattered T'storms become numerous along the immediate coast as some shortwave energy aloft passes east southeast from central GA into SC and helps increase lift and instability there as the Atlantic seabreeze hovers along the coastline through the afternoon. Less coverage expected along the NE FL coast especially from Jacksonville southward due to suppression effects from the ridge and less shortwave energy influence aloft. A strong thunderstorm may produce briefly gusty winds 40-50 mph, with locally heavy downpours and frequent lightning.

The predominant west to west southwest flow around the surface ridge south of the area and a trough to the northwest will lead to hot temperatures in the mid to upper 90s inland today with mid 90s at the coast as well as the Atlantic seabreeze not likely moving onshore beyond the beachfront communities this afternoon. The hot temperatures and moist, muggy dewpoints in the mid to upper 70s will create heat indices well over 100 peaking 108-110 today. Therefore, a heat advisory is in effect from Noon to 7PM today before temperatures and heat indices fall near sunset.

Tonight, a few thunderstorms may linger near the coast, before shifting and weakening as they move eastward due to more west to northwest upper level flow. After lingering mid to high level storm clouds disperse by midnight, skies will become mostly clear. Lows will be above normal in the mid 70s inland and the upper 70s along the coast.

SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/

Main Highlights This Period:

- Daily Isolated to Scattered Afternoon Thunderstorms, some of which could be strong

- Heat Index Values near Heat Advisory levels each day with near record high temperatures Wednesday, the area will continue to be influenced by a deep layer high pressure ridge in the Gulf and low pressure troughing along the coast. This will result in prevailing west to northwest flow through the mid levels. Suppressive affects from the ridge aloft and the low amounts of moisture in the lower levels continue to suggest near or below average rain chances, generally in the 20-40 percent range. Main areas of higher POPs will be along the east coast and around the I-10 corridor. Slight rain chances expected in the evening hours, and some lingering weak convection remains possible after midnight but confidence is low. The main concern will be the heat with heat index values near heat advisory with fairly high likelihood of an advisory. Highs in the mid to upper 90s are anticipated.

For Thursday, subtle changes occur as the mid level ridge over the Gulf retrogrades toward the north central Gulf, while east coast troughing dips further south, and gradually into our northern zones by late Thursday. Models suggest still a decent chance of showers and storms, about 30-40 percent from I-10 southward, and about 20- 30 percent toward inland southeast GA. Isolated storms expected in the evening as well, and there is some potential for overnight activity given the disturbances aloft in the northwesterly flow but for now given low confidence/coverage will advertise 10 percent chance. Of course, little relief from the heat with highs in the mid to upper 90s. Heat indices are likely to reach heat advisory criteria so have medium to high confidence we'll need an advisory.

Each day, a few storms may be strong given steep low level lapse and the fairly high PWAT air. Noted downdraft CAPE of about 700-900 J/kg are seen in NAM BUFR soundings.

LONG TERM /FRIDAY THROUGH MONDAY/

Main Highlights This Period:

- Scattered Afternoon/Evening Thunderstorms Each Day

- Heat Advisory Potential Each Day. Near record high temperatures

- Higher chances for thunderstorms on Friday

Surface high pressure ridge continues to push south of the area Friday into the weekend, as prefrontal troughing and a weak front move south along the east coast. Low level troughing is noted in guidance over our north parts of the forecast area Saturday into Sunday. It looks like some enhanced chance of showers and storms each day, probably near or above average. There may be some tapering off of chances on Monday but confidence at the day 7 day frame is low. Above average temperatures will continue into the weekend with daily max temps rising into the mid to upper 90s and heat index values reaching 105 to 110 and likely reaching heat advisory levels during periods of peak heating. The only thing that could hamper reaching heat advisory is if cloudiness develops quickly and convection begins by early afternoon hours and limits our heat indices.

AVIATION /06Z TUESDAY THROUGH 06Z WEDNESDAY/

VFR conditions observed at this hour will trend to MVFR at VQQ with restrictions for LIFR visibility/ceilings in the pre dawn morning hours 07-11Z, otherwise VFR at all other sites through sunrise.

Surface high will be centered over the northeast Gulf waters into central FL today with westerly to west southwesterly winds 5-8 knots after 14Z with low level cumulus 1.5 kft rising to 3.0-4.0 kft this afternoon. The westerly flow and Gulf seabreeze will develop T'storms along the pinned Atlantic seabreeze that will slowly shift onshore past SGJ and remains near SSI and likely not move through CRG. Have VCTS coverage of T'storms over the coastal and Duval TAF sites after 19Z with PROB30 group at SSI where higher moisture and instability will focus better T'storm coverage which could bring restrictions for MVFR ceilings/IFR visibility from heavy downpours.

Convection will end after 00Z but VCSH may continue a bit at SSI until 02Z. Light south to southwest winds and decreasing mid and high clouds are expected to end the TAF period.

MARINE

Today, Atlantic high pressure will shift south and westward as a trough forms over the southeastern states, with winds prevailing west-southwesterly this morning and more westerly the rest of the week. Each afternoon, the sea breeze will shift winds southeasterly over the near shore waters through the upcoming weekend, followed by southerly evening wind surges which may briefly increase to near caution levels. Scattered thunderstorms may push east from the coast into the coastal waters this evening. Scattered mainly afternoon and evening thunderstorms will remain possible each day through the upcoming weekend.

Rip Currents: A lower end moderate risk may continue at the northeast FL beaches this afternoon as breezy onshore winds develop following the passage of the sea breeze. Low surf heights will likely yield a low risk at the southeast GA beaches. A low risk is then expected from Wednesday through at least Saturday at area beaches as offshore winds and low surf heights prevail.

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 today through Wednesday and forecast to be around 20-40%. A few strong thunderstorms may produce gusty outflows with locally erratic winds.

Temperatures will rise into the mid 90s inland and lower to mid 90s at the coast today and Wednesday with peak heat index values rising to heat advisory levels to about 106-110 into midweek. A heat advisory is in effect for parts of the area today, and may be needed again on Wednesday. Patchy high daytime dispersions expected today into Wednesday as mixing heights increase 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.

CLIMATE

Daily record high temperatures are possible by Thu-Fri:

Thursday, August 13th: KJAX: 99/2023 KAMG: 100/9999 KCRG: 96/2023

Friday, August 14th: KJAX: 99/2023 KGNV: 97/2023 KAMG: 101/2023 KCRG: 98/2023

PRELIMINARY POINT TEMPS/POPS

AMG 95 76 95 76 / 40 20 20 10 SSI 93 79 95 79 / 60 30 30 10 JAX 96 75 94 75 / 60 40 50 10 SGJ 93 76 94 76 / 30 20 40 20 GNV 95 74 93 75 / 30 0 20 10 OCF 95 74 94 75 / 20 0 10 10

JAX WATCHES/WARNINGS/ADVISORIES

FL...Heat Advisory from noon today to 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 from noon today to 7 PM EDT this evening for GAZ153-154-165-166. MARINE...None.