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

- Continued Hot Heat Index 105-108 deg Today

- Stormy Today & Saturday. Isolated Strong to Severe Storms Afternoon & into Evening. Hazards: Gusty Winds (40-60 mph), localized flooding, & frequent lightning. Daily isolated to scattered afternoon & evening storms Sunday - Thursday

- Moderate Afternoon Rip Current Risk Today

NEAR TERM /THROUGH TONIGHT/

Highlights through Tonight:

- Heat advisories in effect for portions of the area this afternoon

- Potential for strong to severe thunderstorms this afternoon and evening

Mid level shortwave aloft across inland SE GA just north of the FL/GA border has triggered scattered showers and storms this morning across Clinch/Echols/Hamilton counties. This feature will slowly drift off to the E-NE this afternoon/evening and interact with sea breeze and outflow boundaries to produce scattered to numerous showers and storms, mainly from the I-10 corridor of NE FL northward across all of SE GA. Cooler than normal temps aloft from -7C to -8C at 500 mb will help to increase mid level lapse rates and expect scattered strong to isolated severe storms with gusty winds to 40-60 mph along with heavy downpours and localized flood threat due to the slow storm motion towards the E-NE around 10 mph or less. This activity will then interact with southward moving frontal boundary convection near the Altamaha River Basin and expect numerous to widespread showers and storms later this evening into the early overnight hours of inland SE GA near the Altamaha Basin that will continue the heavy rainfall threat, although much of this local area has been rain-free for several days, so mainly urban areas will have the higher flood threat tonight.

As far as temps go this afternoon/evening, the mid level shortwave and abundant clouds have lessened the coverage of heat advisory conditions, but just enough pockets of Max Temps into the lower to middle 90s will produce some heat indices of 105-109F, so will keep current heat advisory in place for now. Low temps tonight should drop into the lower/middle 70s inland, mostly due to rain cooled temps for most locations, with upper 70s along the Atlantic Coastal areas.

SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/

Main Highlights This Period (Saturday and Sunday):

- Strong to isolated severe thunderstorms Saturday

- Localized Flooding Rain Risk Saturday

- Drier Sunday for Southeast GA

Unsettled weather continues Saturday with likely ongoing areas of morning showers and isolated storms moving inland from the Gulf coast region with the approach of the surface front under the meandering mid level trough across the area aloft. Convection will spread eastward across the area from the southwest through the day along the surface front across southeast GA and along the sea breezes across northeast Florida into the afternoon, with convection ongoing into the evening along the surface front as it settles southward toward northeast Florida. By Sunday, the surface front is expected to be near the Fl-Ga state-line, trailed by a drier and more stable northwest flow across southeast GA with less than 10% chance of rain Sunday while enough moisture lingers south of the front across northeast FL to continue isolated to scattered shower and thunderstorm chances into the afternoon along a dominant west coast sea breeze. Isolated strong to briefly severe storms will be possible both Saturday and Sunday with cooler temperatures aloft and some lift under weak PVA.

Heat indices will trend lower this weekend compared to earlier in the week thanks to more clouds cover and storminess on Saturday and then drier air filtering in across southeast GA Sunday. Saturday highs will top out in the low to mid 90s and then Sunday highs warm back into the upper 90s for southeast GA north of the front. Heat index values will hover around 105 for most locations each day, but there will be periods of 105-109 deg in cloud breaks especially toward the coast. Confidence not high enough for prolonged enough duration of heat advisory for Saturday at this time.

LONG TERM /MONDAY THROUGH THURSDAY/

Main Highlights This Period (Monday through Thursday):

- Hot and Drier Monday

- Storminess Returns Tuesday

The broader pattern will keep an initially drier northwesterly flow across the region Monday limiting rain chances Monday to mainly northeast Florida. Deeper moisture returns by Tuesday with increasing rain chances as another mid level trough axis begins to deepen down across the southeast region with a return of more scattered afternoon and evening storms under a prevailing west coast sea breeze regime as surface fronts nose southward across GA toward the end of the week.

The hottest day will be Monday as a dry airmass heats up in to the mid/upper 90s. Above normal temperatures are expected to continue through the week with highs generally in the low 90s Tuesday onward with heat index values generally below local heat advisory criteria at this time.

AVIATION /18Z FRIDAY THROUGH 18Z SATURDAY/

Scattered to numerous showers and storms are expected this afternoon and evening in the 18Z-00Z time frame and will need to time out PROB30 and TEMPO groups for gusty TSRA activity and MVFR CIGS and potential IFR VSBYS. Timing will be earliest from 18-00Z for the NE FL TAF sites and 20-02Z for SSI at this time. Convection should start to fade after sunset (00Z) but may linger at SSI until the 04- 06Z time frame, then return to VFR conds at all TAF sites with low chances of fog for Saturday morning/sunrise and will leave out for now. Timing for showers/storms on Saturday should occur after the current 18Z end time.

MARINE

A frontal zone will extend across the Carolinas and into Georgia this period, with a high pressure ridge to the southeast. Rounds of mainly afternoon and evening showers and thunderstorms can be expected each day. Brief southerly wind surges are expected during the late afternoon and evening hours, but are expected to remain below Small Craft Exercise Caution levels through the period.

Rip Currents: Offshore winds will prevail throughout the morning hours, along with low surf heights, during the next several days. With the outgoing tide occurring later in the afternoon, the overall risk will be low today and low to low end moderate this weekend as an afternoon seabreeze brings light south to southeast winds to the beaches. Surf/breakers will remain 1-2 feet or less.

FIRE WEATHER

Unsettled weather will continue through Saturday with waves of showers and storms across the area with a front approaching today and lingering across the area tomorrow. Isolated strong to severe storms are possible, mainly during the afternoon and evenings capable of strong wind gusts, locally heavy rainfall and frequent lightning. Prevailing southwest winds today and Saturday become more northwest across southeast Georgia on Sunday as the front stalls across northeast Florida. The drier northwest flow will bring lower humidity and mostly dry weather to southeast Georgia Sunday with minimum humidity between 35-40% while scattered to isolated afternoon showers and storms impact northeast Florida where higher moisture will continue. Hotter temperatures on Sunday will bring higher dispersion to areas near the Altamaha River basin while dispersion in the Good range prevails for most other locations.

CLIMATE

Near record high temperatures are possible at some of our designated climate sites during the next few days:

Friday, August 21: KJAX: 101/1900 KGNV: 99/1983 KAMG: 100/1980 KCRG: 99/2016

PRELIMINARY POINT TEMPS/POPS

AMG 96 72 93 72 / 60 70 70 10 SSI 91 76 90 76 / 40 40 70 20 JAX 94 74 93 74 / 50 30 60 20 SGJ 93 75 93 74 / 30 20 40 10 GNV 93 73 91 73 / 30 10 60 20 OCF 93 73 91 73 / 20 10 40 20

JAX WATCHES/WARNINGS/ADVISORIES

FL...Heat Advisory until 7 PM EDT this evening for FLZ021-023-024- 030-031-035-038-120-124-125-132-136>138-220-225-232-233- 236-237-322-325-333-422-425-433-522-533-633. GA...Heat Advisory until 7 PM EDT this evening for GAZ136-152>154- 162-163-165-166-264-350-364. MARINE...None.