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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 and Marginally Severe Thunderstorms This Afternoon and again Late Tonight. Main hazards will be strong wind gusts today with an isolated tornado possible with overnight Thunderstorms

- Building Seasonably Hot Conditions Through the Weekend. Peak Heat Index between 100-107 degrees this afternoon.

- Daily thunderstorm chances continue Friday and through the weekend, with strong to severe storms possible Friday

- Valdosta Radar is Out of Service. Please utilize other area radars for active weather this afternoon and tonight.

NEAR TERM /THROUGH TONIGHT/

Main Highlights Today and Tonight:

- Strong Afternoon Storms Possible along the Atlantic Coast

- Late Night Marginal Severe Thunderstorm Threat, Mainly Inland SE GA and Suwannee Valley

- Seasonably Hot Afternoon: Heat Index 100-107 degrees.

Another day with a southwesterly conduit Gulf moisture pushing into the area. This will set up another early start to shower activity this morning, mainly across the Suwannee Valley before thunderstorm potential increases this afternoon along the pinned Atlantic sea breeze. Heat will build more today which will leverage a stronger Atlantic sea breeze that should move a few miles inland early this afternoon, the southwesterly flow and ample instability will be sufficient for scattered thunderstorms to develop along the coast and then proceed into the coastal waters during the afternoon hours. A few of the storms along the coast may pulse to strong to marginally severe levels, especially as boundaries begin to collide. Additional afternoon convection is likely across the Suwannee Valley and inland SE GA as a "masked" Gulf breeze pushes inland.

As mentioned the heat will build today but decent mixing should mix near-surface moisture enough to keep peak heat index just a bit below Heat Advisory levels this afternoon. But it will still be seasonably hot with heat index in the 102-107 degree range with the high end of that range favored along the coast. Low level temperatures will be above the climo 90th percentile, so actual highs temperatures in the mid/upper 90s are very likely to materialize across much of NE FL this afternoon where cloud cover should be less.

Tonight, attention turns toward the upper shortwave trough associated with the post-tropical remnants of Arthur. That shortwave will graze our inland areas late tonight as it ejects northeastward. High resolution has been consistently bringing a decaying convective complex of thunderstorms into inland SE GA zones around midnight and then fade in intensity as it moves east-southeastward toward the Atlantic coast through the early morning hours Friday. Given the low level jet at 850mb, around 40-50 kts, the main concern will be strong outflow winds, possibly at severe levels for in "bowing" segments embedded within the cluster. Though probs are low, can't rule out the possibility of an isolated quick-spin up tornado, especially across inland SE GA. There's still considerable uncertainty in how long convection will be sustained given the degraded surface instability but it could maintain and extend a severe thunderstorm threat into daybreak Friday, mainly from I-10 northward.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/

- Isolated Strong to Severe T'storms Friday - Numerous to Widespread Showers and T'storms Saturday - Hot and Humid Conditions Friday into Saturday

Friday, a cold front will sink SE towards the area, trailing the remnants of Tropical Storm Arthur, bringing high moisture values into the area with Precipitable Water levels (PWATs) in excess of 2 inches (above the 90th percentile compared to climatology). The abundance of moisture will create mostly cloudy skies, but lift from the incoming front at the surface and instability aloft from shortwave energy over area will create numerous to widespread showers and T'storms over SE GA. More breaks in the clouds further south and WSW low level flow will allow the Gulf seabreeze a head start towards the NE FL coast, spurring afternoon/early evening scattered to numerous T'storms. Despite a lack of strong shear, water loading from a near saturated atmospheric column and strong low level instability will allow for isolated strong to severe T'storms developing along seabreeze interactions and outflow/storm mergers capable of wet downburst wind gusts up to 50-60 mph. Other T'storm hazards of locally heavy downpours and frequent lightning also expected.

Highs on Friday will be near normal over NE FL into the upper 80s and low 90s while staying below normal over SE GA due to the clouds and showers and T'storms with highs only in the mid 80s. Max heat index values will be 100-104 for portions of NE FL south of I-10.

Friday night, convection will dissipate but scattered showers will remain drifting eastward across the area as the frontal boundary sinks to the FL/GA border through the pre-dawn morning hours. Lows will be muggy in the mid to upper 70s.

Saturday, the frontal boundary will sink into NE FL as weak high pressure moves north of the region into the upper OH/TN valleys. This will promote the highest chances for showers and T'storms more over NE FL as lift from the front, shortwave energy aloft, and high moisture content combine to create widespread showers and T'storms from mid to late morning persisting through the early evening hours with diminished coverage behind the front across SE GA. Winds will shift from westerly to WNW with skies staying mostly cloudy. Clouds will limit the degree of low level instability compared to Friday, but gusty winds to 40 mph, frequent lightning, and locally heavy downpours will be the main hazards. Some ponding of water and minor flooding potential expected for NE FL Saturday with slower storm motions pushing activity ESE. Highs on Saturday will be in the low 90s over NE FL and around 90 over SE GA.

Saturday night, skies will become partially clear with T'storms ending by 10PM and any lingering scattered showers ending a little after midnight, lows will fall to the lower 70s over SE GA and the mid 70s over NE FL. Light westerly winds will become calm inland.

LONG TERM /SUNDAY THROUGH WEDNESDAY/

Main Highlights This Period:

- Heat index values increasing to near Heat Advisory levels next week - Decreasing chances for showers Afternoon and Evening T'storms Sunday through next week

Sunday, slightly drier air aloft will arrive across SE GA and into portions of NE FL as the front stalls near north central FL. Light westerly winds will push the Gulf seabreeze eastward towards the SE GA and NE FL coast, kicking off widely scattered T'storms in the strong diurnal heating. But, the westerly flow will limit the advancement of the Atlantic seabreeze to east of I-95.

Monday, drier air will lower PWATs to 1.50 to 1.75 inches and along with low to mid level subsidence due to ridging building over the Gulf and FL peninsula will widely isolated T'storm activity to near the Altamaha river as a fast moving trough moves north of the region. Mostly sunny skies will allow for hot conditions with highs into the mid to upper 90s, likely pushing heat index values to 104-108 very close to heat advisory levels.

Tuesday, a front will approach from the north with WSW flow and an uptick in moisture allowing for widely scattered T'storms. But, the very hot conditions will continue with potential heat advisory conditions as values climb to 106-110 as dewpoints remain in the mid to upper 70s ahead of the front.

Wednesday, the front will sink into the area with more clouds and WNW flow, but also highs decreasing back to the low 90s which may curve heat advisory conditions. Uncertainty remains on exactly where the front stalls, so keeping scattered chances for T'storms at this time.

Near normal temperatures Sunday will rise to above normal next week.

AVIATION /06Z THURSDAY THROUGH 06Z FRIDAY/

Light southwesterly winds will become breezy around 15z with gusts 15-20 kts and VFR cloud cover at local TAF sites. A developing area of MVFR low stratus inland this morning across inland southeast GA airfields. The southwesterly flow will trigger early showers again today with increasing TSRA chances at all coastal airfields. Inherited PROB30 groups for convection were largely maintained, however, increased confidence at KSGJ to 50-60% chance with a TEMPO for TSRA and IFR impacts and gusty erratic winds. Convection will push into the Atlantic during the late afternoon and otherwise fade through the evening. Though outside of the current forecast window, there is potential for TSRA early Friday morning.

MARINE

Persistent offshore flow continues across the waters into the weekend. Offshore winds will become quite breezy this afternoon, possibly near 20 knots in the outer coastal waters. A weak front trailing a weak low pressure to the north will stall across the Georgia's coastal waters Friday night. Numerous showers and afternoon thunderstorms are expected to develop along front as it dissipates over the weekend. Weaker offshore flow is likely through the first half of next week as another front approaches and likely stalls just north of the waters.

Rip Currents:

A general low risk of rip currents continues today and likely through the end of the week as surf remains only in the 1-2 ft range in offshore flow.

FIRE WEATHER

Moist and unstable airmass will continue afternoon/early evening scattered to numerous T'storms today as west to southwest winds allow the Gulf seabreeze to move quickly eastward to the Atlantic coast before interacting with the pinned Atlantic seabreeze near the Atlantic coast. T'storms will include heavy downpours and locally heavy rainfall, frequent lightning, and gusty winds with isolated strong to severe T'storms this afternoon. A front will sink towards the area Friday and move through Northeast Florida Saturday with widespread showers and T'storms. The front will stall near north central or central Florida Sunday with less coverage of T'storms.

Favorable transport winds and mixing heights will lead to areas of high afternoon dispersion values today along and west of I-95. Good level dispersions expected during each afternoon Friday into the weekend as more clouds limit mixing heights while transport winds decrease slightly as the front settles south of the area by Sunday.

Temperatures will be hot today and along with elevated humidity will create heat index values up to 102-106 near the coast and across Northeast FL. Highs will decrease to the low 90s Friday into the weekend, but high humidity levels will continue.

FOG POTENTIAL AND OTHER REMARKS: Areas that receive heavier rainfall may also experience patchy late-night and early-morning fog.

EQUIPMENT

The WSR-88D Radar located near the Moody AFB near Valdosta is offline due technical problems. Technicians are awaiting critical parts to restore functionality. During the outage please utilize other area radars...KJAX, KTLH, or KJGX.

PRELIMINARY POINT TEMPS/POPS

AMG 90 75 85 73 / 70 60 90 40 SSI 93 80 91 77 / 70 30 70 40 JAX 96 79 92 76 / 50 20 60 40 SGJ 96 78 93 77 / 60 20 50 20 GNV 95 79 92 75 / 20 10 50 30 OCF 94 79 91 77 / 20 10 30 20

JAX WATCHES/WARNINGS/ADVISORIES

FL...None. GA...None. MARINE...None.