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

- Dangerously Hot Conditions Continue During the Next Week. Extreme Heat Warnings for Brantley, Glynn and Camden Counties in Southeast GA Today. Heat Advisories Elsewhere. Daily Heat Advisories and Extreme Heat Warnings Likely through Next Week

- Strong to Isolated Severe Thunderstorms Possible Across Inland Southeast GA this Afternoon and Evening. Widely Scattered Afternoon and Evening Thunderstorms are Possible Elsewhere.

- Strong to Severe Storm Hazards: Damaging Wind Gusts of 40-60 mph, Frequent Lightning Strikes, Heavy Downpours.

- Slow Storm Motion Later Today May Result in Localized Flooding, Especially at Urban and Normally Flood Prone Locations Across Interior Southeast GA.

- Daily Isolated to Scattered Afternoon and Evening Thunderstorms Next Week.

NEAR TERM /THROUGH TODAY/

Main Highlights:

- Extreme Heat Warning for Brantley, Glynn and Camden Counties in Southeast GA from 11 AM - 8 PM Today.

- Heat Advisory Conditions Elsewhere Today. - Scattered Thunderstorms this Afternoon and Evening, with Strong to Isolated Severe Storms Possible trough this Evening Across Southeast GA.

- Strong to Severe Storm Hazards: Wind Gusts of 40-60 mph, Frequent Lightning Strikes, and Heavy Downpours.

Overnight surface analysis depicts Atlantic high pressure (1025 millibars) centered to the east of the Bahamas and extending its axis westward across the FL peninsula and across the northern and central Gulf. Aloft..."Heat Wave" ridging was positioned over the lower Mississippi Valley, with this feature extending its axis eastward across the Deep South. Latest GOES-East derived Total Precipitable Water imagery indicates that deep tropical moisture remains in place across most of our area, with PWATS across northeast and north central FL generally in the 2 - 2.3 inch range. PWATs are a little closer to mid-August climatology across north central FL, where values were generally in the 1.8 - 2 inch range. High altitude debris clouds leftover from Friday evening convection were gradually thinning over the Suwannee Valley and southeast GA, while fair skies prevailed across the rest of northeast and north central FL. Temperatures and dewpoints were in the 70s area-wide as of 08Z.

"Heat Wave" ridging centered over the lower Mississippi Valley will continue to extend its axis eastward across the Deep South today, allowing highs to soar to the mid and upper 90s at most locations. Dewpoints remaining in the mid 70s inland and the upper 70s at coastal locations this afternoon will allow heat indices to rise to the 108-112 degree range at most locations, while values at or above 113 degrees are forecast across most of Brantley, Glynn, and Camden Counties in southeast GA, where an Extreme Heat Warning has been posted, beginning at 11 AM. Heat Advisories have been posted for the rest of our our area from 11 AM - 8 PM this evening.

Stronger subsidence associated with the deep-layered ridge center will remain west of our area, but low and mid level Atlantic ridging extending across central FL could keep PWATs slightly lower, but still close to climatology, across north central and coastal northeast FL today. Deep tropical moisture in place elsewhere should allow for scattered convection to develop along inland moving sea, lake, and river breezes during the mid to late afternoon hours. Otherwise, a subtle low and mid level trough positioned between the deep layered ridge over the lower Mississippi Valley and the Atlantic ridge axis may trigger strong to isolated severe thunderstorms convection across portions of inland southeast GA late this afternoon that may linger through around midnight tonight before dissipating. Colliding convective outflows across southeast GA should allow for storms to pulse, with downburst winds of 40-60 mph, frequent lightning strikes, and torrential downpours possible. Ridging aloft over our region will likely yield slow and erratic storm motion, with localized flooding possible where storms develop, especially at urban and normally flood prone locations.

Convection will dissipate early this evening across northeast and north central FL and towards midnight across southeast GA. Thinning debris clouds and diminishing winds during the predawn and early morning hours on Sunday resulting in lows falling to the mid 70s inland and the upper 70s to around 80 at coastal locations.

SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/

Main Highlights This Period:

- Isolated Strong to Severe Storms Sunday and Monday Afternoon/Evening.

- Heat Index Values Near or Above Heat Advisory Each Day.

Nearly stacked high pressure will be the main and dominant feature for the area on Sunday, as a southwesterly flow and some subsidence helps to boost high temps into the mid to possible upper 90s on Sunday. The subsidence will help to suppress diurnal convection slightly, with only isolated to widely scattered activity expected Sunday with PoPs generally in the 30-40% range across the region. The best chances for convection and especially stronger convection looks to be generally along the coast/I-95 corridor in closer proximity to the Atlantic sea breeze that will be nearly pinned at the coast. The lower coverage of convection will also help many locations get above normal daytime heating, further supporting high temps above normal as well as likely Heat Advisory/possible Extreme Heat type of conditions.

Surface high pressure drops slightly southward on Monday thanks to a cool front that approaches and stalls over southeast GA by Monday Morning. There looks to be enough of a surge of drier air aloft, combined with the subsidence still in place, to keep chances for showers and storms generally isolated to widely scattered once again, with parts of inland southeast GA expected to see little to no afternoon showers and storms. Similar to Sunday, lower convective coverage will lead to high temps in the mid to upper 90s on Monday, with some locations reaching 100 certainly not out of the question, especially over inland GA with more time baking in the sun. Heat headlines appear likely once again Monday. .

LONG TERM /MONDAY THROUGH FRIDAY/

Main Highlights This Period:

- Hazardous Heat Continues into Next Week, with Daily Heat Headlines Possible.

- Isolated to scattered thunderstorms each afternoon and evening, some which could become strong.

A frontal boundary will remain nearly stationary across southern Georgia for the long term period, persisting generally southwest flow and hot conditions for mid to late next week. The focus for convection will be across northeast Florida Tuesday before spreading across the entirety of the region as "waves" of moisture move along the boundary. Lingering subsidence will keep PoPs from reaching higher than around 50-60%, however. Prolonged, hazardous heat is expected to continue for most of the long term, but especially for Tuesday/Wednesday with high temperatures generally in the mid to upper 90s and afternoon heat index values reaching 106-113 degrees each day.

AVIATION /06Z SATURDAY THROUGH 06Z SUNDAY/

VFR conditions will prevail at the regional terminals through at least 18Z Saturday. Widely scattered showers and thunderstorms will begin developing near the terminals towards 19Z, initially near GNV and VQQ, with activity then potentially shifting towards JAX and CRG after 20, with convection then potentially impacting SSI after 22Z. Confidence was high enough at these terminals to include PROB30 groups for brief surface wind gusts around 25 knots and MVFR visibilities during heavier downpours. Showers and thunderstorms will likely diminish in coverage before 03Z. Confidence was only high enough for vicinity thunderstorm coverage after 20Z at SGJ. Lingering showers should then dissipate overnight, and VFR conditions should then prevail by 04Z Sunday at the regional terminals. Light southwest or westerly surface winds will remain sustained around 5 knots or less at the SSI and SGJ through around 13Z, followed by westerly surface winds increasing to 5-10 knots by 15Z. Westerly surface winds will become sustained around 5 knots at the inland terminals by 14Z, followed by winds shifting to southwesterly at 5-10 knots at GNV and VQQ by 18Z. The Atlantic sea breeze boundary will develop at coastal locations after 16Z, shifting surface winds at SGJ to easterly around 10 knots before 18Z, while winds shift to southerly around 10 knots at SSI towards 18Z. Winds will then shift to southwesterly or westerly around 5 knots after 00Z Sunday.

MARINE

Atlantic high pressure will build westward across the Florida peninsula today, with light southwest to westerly winds this morning shifting to southeasterly and becoming breezy this afternoon as the Atlantic sea breeze pushes inland. Surface winds will then shift to southerly this evening and back to southwesterly after midnight as speeds diminish. Only isolated to widely scattered thunderstorms are expected to develop this afternoon and evening, mainly for the waters north of St. Augustine. The axis of Atlantic high pressure will then shift southward on Sunday and Monday as a frontal boundary pushes into the southeastern states, with this feature stalling just north of the Georgia waters by midweek. Southwest to westerly winds will prevail from Sunday through midweek, with evening wind surges likely increasing speeds to Caution levels. Only isolated to widely scattered afternoon and evening thunderstorms are expected on Sunday and Monday, with coverage potentially increasing towards midweek as the frontal boundary approaches from the north.

Rip Currents: Breezy onshore winds developing this afternoon will combine with a long period easterly ocean swell and the outgoing tide to create a low end moderate risk at area beaches today. Prevailing offshore winds on Sunday and Monday will likely lower the risk at the southeast GA beaches, where surf heights will fall below 2 feet. Onshore winds developing on Sunday afternoon may keep a lower end moderate risk in place at the northeast FL beaches, where surf heights will generally remain around 2 feet this weekend. Prevailing offshore winds during the early and middle portions of next week will likely yield a low risk at all area beaches.

FIRE WEATHER

- Heat Headlines In Effect Today.

- Areas Of High Dispersions Inland Southeast GA on Monday.

Hot conditions are expected to persist through the rest of the weekend and into at least the start of next week, with heat headlines likely to continue each day for most or all of the region. This will come with a flow direction generally out of the southwest to west through the next several days, as well as slightly lower chances for afternoon/evening showers and thunderstorms, especially over interior GA. Good mixing, especially outside of any showers or storms, will result in mostly good dispersions, which could be high over portions of inland GA late weekend.

Fog Potential: Significant fog development is not expected. Any late-night or early-morning fog should be shallow and patchy, mainly in areas that receive locally heavy rainfall. Gusty and erratic winds are often possible within and nearby any stronger showers or storms.

CLIMATE

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

Saturday August 15th: KJAX: 99/1956 KGNV: 100/1918 KAMG: 99/1995 KCRG: 97/2011

Sunday, August 16th: KJAX: 97/1957 KGNV: 97/1918 KAMG: 100/1995 KCRG: 95/2022

Monday, August 17th: KJAX: 99/1954 KGNV: 97/1954 KAMG: 104/1995 KCRG: 97/2005

Tuesday, August 18th: KJAX: 98/1954 KGNV: 98/1954 KAMG: 105/1995 KCRG: 96/2023

PRELIMINARY POINT TEMPS/POPS

AMG 97 75 96 77 / 40 40 20 10 SSI 96 78 97 80 / 30 30 20 20 JAX 96 75 96 76 / 40 40 30 20 SGJ 95 77 96 78 / 30 20 30 10 GNV 96 74 95 76 / 40 20 30 10 OCF 96 74 96 76 / 30 10 10 10

JAX WATCHES/WARNINGS/ADVISORIES

FL...Heat Advisory from 11 AM this morning to 8 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 11 AM this morning to 8 PM EDT this evening for GAZ132>136-149-151-162-163-250-264-350-364. Extreme Heat Warning from 11 AM this morning to 8 PM EDT this evening for GAZ152>154-165-166. MARINE...None.