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 Weather Continues this Week. Extreme Heat Warning and Heat Advisories Today from 11 AM 8 PM. Heat Advisory for most of the area Wednesday. Heat Advisories possible again Thursday through Friday

- Scattered to Numerous TStorms Each Afternoon & Evening through. Main Impact Areas through Thursday: Northeast and North Central FL. Strong Storms are Possible Each Day, Mainly Along the I-95 Corridor. Primary Hazards: Wind Gusts of 40-55 mph, Frequent Lightning Strikes, and locally heavy rain.

NEAR TERM /THROUGH TONIGHT/

Main Highlights through Tonight:

- Dangerous Heat Index & Near Record High Temperatures - Extreme Heat Warnings and Heat Advisories through 8 pm today. - Strong Thunderstorms Late Afternoon and Evening Northeast FL

Latest early afternoon heat index values were approaching 108-110 inland to 110-115 deg at the coast. Extreme Heat Warning continues for all of northeast FL, Echols county and coastal southeast GA through 8 pm with a Heat Advisory for the remainder of inland southeast GA.

Dominant surface trough continues draped across north GA with mean layer high pressure extending from across the central Gulf of America to across the across the Bahamas. A few low level surface troughs extended south of the parent trough, one sliding south of Marion county with convection into north central FL. Convection is still expected to resurrect later this afternoon and into the early evening with the main focus area across northeast Florida where deeper moisture (PWATs > 2 inches) combine with mesoscale boundaries including the sea breezes and weak troughs. Drier air mixing down across southeast GA generally north of Waycross to Jesup will limit convective coverage into the evening with rain chances < 20% while the higher rain chances of near 60% were advertised between I-95 and the Highway 301 corridor of northeast Fl between 5 pm and 8 pm this evening. The main hazards in resultant storms will be localized heavy rainfall and wet downbursts in storm mergers.

Convection will tapper off inland into the evening with lingering stratiform through about midnight across the Suwannee River Valley. Muggy overnight conditions continue with lows in the mid to upper 70s.

SHORT TERM /WEDNESDAY THROUGH FRIDAY NIGHT/

Main Highlights This Period (Wednesday and Thursday):

- Greatest chance for thunderstorms this period over NE FL during the afternoon and evening hours, with a few strong storms possible

- Heat Advisories in effect for Wednesday, another likely needed on Thursday

Predominately northwest/west steering flow Wednesday will bring in drier air across southeast Georgia, and allow the Gulf sea breeze to push far inland and meet the Atlantic sea breeze closer to the east coast. Overall, precipitation chances will be <30% across southeast Georgia, and highest storm chances will be east of Gainesville towards the northeast Florida beaches. Hazardous heat continues on Wednesday, with high temperatures in the mid to upper 90s, potentially near 100 for some inland southeast Georgia locations. Maximum afternoon heat index values will be around 106-113 degrees for northeast Florida and the Georgia coast, drier air over inland southeast Georgia will keep afternoon heat indices near 100-103 despite highs in the upper 90s. Best chances for reaching 100 degrees will be along the Altamaha River Basin.

Thursday, steering flow shifts more southerly/southwesterly, allowing the Atlantic and Gulf sea breezes to meet in a more central location, increasing storm chances between I-75 and I-95. Some moisture will recover over inland southeast Georgia, bringing scattered rain and storm chances. Once again, high temperatures will be in the mid to upper 90s and near 100 across inland southeast Georgia. Another Heat Advisory will likely be needed for at least the southeast Georgia coast and portions of northeast Florida.

LONG TERM /SATURDAY THROUGH TUESDAY/

Main Highlights This Period (Friday through Monday):

- Near Record Heat and Dangerously High Heat Indices Continue on Friday

- Scattered to Numerous Afternoon and Evening Thunderstorms Each Day from Friday through the Upcoming Weekend

A front will be lingering across Georgia through this period, enhancing moisture across the area Friday and Saturday as southwesterly flow continues. Scattered to numerous showers and storms are expected Friday and Saturday, with the southwest winds promoting strong storm potential closer to the east coast where the two sea breezes will interact. By Sunday, drier air moves in again over southeast Georgia, lowering precipitation chances Sunday onward. Highs in the mid to upper 90s continue Friday, 'cooling' slightly this weekend into the lower to upper 90s. Most of the area will again approach Heat Advisory criteria on Friday with max afternoon heat index values possibly finally remaining below Advisory criteria this weekend.

AVIATION /18Z TUESDAY THROUGH 18Z WEDNESDAY/

Cumulus clouds were slow to develop with shower and thunderstorm onset delayed until late afternoon and into the early evening. Adjusted TAFs for latest timing and only continued with TEMPO group for TS for VQQ where > 60% chance of rain was advertised. Prevailing WNW to WSW winds 8-12 kts with gusts 15-20 kts will keep the east coast sea breeze pinned offshore with slight backing of winds at SSI, CRG and SGJ to the SSW possible through 00z. Best thunderstorm chances focus inland into the evening so included only VCTS in JAX, CRG, SGJ and GNV through 01z with SSI rain free. Strong storms are possible this evening with the main hazard gusty outflow winds. TEMPO groups for convection will be added/amended as radar trends become resolved. Convection fades inland by 04z with lingering debris clouds gradually fading through the night as WNW winds remain elevated around 5 kts.

MARINE

A surface front will continue to linger across the southeast region with Atlantic coast high pressure extending across the Bahamas. This pattern will continue a prevailing southwest to south wind pattern across the local waters with brief surges near Small Craft Exercise Caution wind criteria in the afternoons and evenings. A daily east coast sea breeze will bring winds south to southeast along the immediate coast. Daily showers and isolated storms will impact mainly the coastal waters east of Florida.

Rip Currents: Prevailing offshore winds and low surf heights will keep a low risk in place through at least midweek at area beaches. Offshore winds will decrease slightly by Thursday and Friday, allowing the afternoon sea breeze to create breezy onshore winds that may result in a lower end moderate risk at the northeast FL beaches on Thursday and Friday.

FIRE WEATHER

- Heat Advisory conditions again Wednesday

- Patchy High Daytime Dispersions Southeast Georgia Wednesday

The region will be between high pressure to the south, and a frontal zone to the north this period. Thunderstorms will be in the forecast each afternoon and evening this period. Overall, drier air will be in place over inland southeast Georgia, but above critical minimum relative humidity values. Patchy high dispersion is forecast for Wednesday afternoon across southeast Georgia, and will be fair to good for the rest of the week. It will be an abnormally hot week, with readings returning to more seasonal levels over the weekend.

Fog Potential: Significant fog formation is not expected. Gusty and erratic winds are possible within stronger thunderstorms.

CLIMATE

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

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

Wednesday, August 19th: KJAX: 99/1900 KGNV: 100/1954 KAMG: 103/1995 KCRG: 97/2010

Thursday, August 20th: KJAX: 101/1900 KGNV: 99/1900 KAMG: 104/1995 KCRG: 98/2016

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

PRELIMINARY POINT TEMPS/POPS

AMG 77 98 74 98 / 10 20 10 30 SSI 79 97 79 95 / 20 10 30 20 JAX 76 97 75 95 / 30 40 30 50 HEAT ADVISORIES AND EXTREME HEAT WARNINGS IN EFFECT TODAY AND WednesdaySGJ 78 95 77 93 / 30 30 20 50 GNV 76 94 75 94 / 50 60 30 70 OCF 77 94 76 94 / 30 60 20 80

JAX WATCHES/WARNINGS/ADVISORIES

FL...Extreme Heat Warning until 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. Heat Advisory from 11 AM to 8 PM EDT Wednesday 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...Extreme Heat Warning until 8 PM EDT this evening for GAZ153- 154-162-165-166. Heat Advisory from 11 AM to 8 PM EDT Wednesday for GAZ153-154- 162-163-165-166-264-350-364. Heat Advisory until 8 PM EDT this evening for GAZ132>136-149- 151-152-163-250-264-350-364. MARINE...None.