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

- Numerous Showers with a Few Embedded Thunderstorms Possible through this Evening, Mainly for Locations South of Interstate 10.

- Fog Formation Possible at Inland Locations During the Predawn and Early Morning Hours on Thursday, with Locally Dense Fog Possible for Interior Southeast GA.

- Daily Afternoon & Evening Thunderstorms from Thursday through Tuesday. Heavy Rainfall Potential Thursday and Friday for Northeast and North Central FL.

- High Risk for Rip Currents at the Northeast FL Beaches through Thursday. Moderate Risk of Rip Currents at the Southeast GA Beaches.

NEAR TERM /THROUGH TONIGHT/

Highlights through Tonight:

- Numerous Showers with a Few Embedded Thunderstorms Possible through this Evening, Mainly for Locations South of Interstate 10.

- Fog Formation Possible at Inland Locations During the Predawn and Early Morning Hours on Thursday, with Locally Dense Fog Possible for Interior Southeast GA.

Afternoon surface analysis depicts an inverted trough extending from the near shore Atlantic waters adjacent to east central FL northeastward to the offshore waters adjacent to northeast FL. This feature was moving slowly northwestward. Meanwhile, high pressure (1021 millibars) extends from the western Atlantic waters near the Outer Banks westward across the southern Appalachians and through the Tennessee Valley and the Ozarks. Otherwise, Tropical Depression Edouard (1004 millibars) was drifting north-northwestward across far eastern Texas. Aloft..."Heat Wave" ridging blankets the southeastern states, with a Tropical Upper Tropospheric Trough (TUTT) feature spinning west-northwestward beneath this ridge along the FL Panhandle coast. Latest GOES-East derived Total Precipitable Water imagery indicates that deep tropical moisture resides for locations south and east of Waycross, GA, where above 2 inches, with locations along and south of the Interstate 10 corridor experiencing values between 2.25 and 2.5 inches. A slightly drier air mass prevails from Waycross and points north and westward, where values were generally around 1.75 inches.

Bands of showers and a few embedded thunderstorms located on the northwestern edge of the approaching inverted trough were spiraling west and southwestward for locations within the deeper tropical air mass, where increasing cloud cover and breezy northeasterly winds were generally keeping temperatures in 85-90 degree range outside of rain cooled locations as of 18Z, with dewpoints in the mid to upper 70s. A paltry cumulus field was in place elsewhere across inland southeast GA within the drier air mass, where temperatures have mostly climbed into the lower 90s, with dewpoints in the low to mid 70s creating heat index values of 100-105 degrees as of 18Z.

Inverted surface troughing will slowly move northwestward towards the northeast FL coast tonight. Bands of showers and possibly a few embedded thunderstorms will continue to move onshore, especially for locations south of Interstate 10, with activity generally moving briskly west or southwestward for locations south of Waycross through the early evening hours tonight. Locally heavy downpours will be possible across coastal northeast FL as well as southern portions of the St. Johns River basin and across north central FL through around sunset, but the quick motion of these rain bands should limit amounts to negate localized flooding. There should be a lull in these coastal bands of showers this evening before another uptick in activity takes place during the predawn and early morning hours on Thursday, with potential impacts to locations along and east of I-95. Otherwise, decoupling winds should allow for low stratus ceilings and fog to develop, especially over the more subsident air mass that currently resides across interior southeast GA and western portions of the Suwannee Valley. Lows tonight will only fall to the mid 70s inland, with a light northeasterly breeze keeping coastal lows in the upper 70s to around 80.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/

Main Highlights This Period:

- Daily shower and thunderstorm potential, with strong storms possible over inland locations.

Continuing onshore flow will bring early morning showers onshore both Thursday and Friday, with rain coverage pushing inland through the morning to early afternoon. By mid afternoon through sunset, expect an increase in storm coverage, primarily for inland northeast Florida where the Atlantic sea breeze meets the slower moving Gulf sea breeze. Several days of heavy rainfall potential will hold the 'Marginal' risk of excessive rainfall for northeast Florida on Thursday, posing a risk to localized flooding. In addition to the flooding threat, gusty winds would be possible with any strong storm development, the highest risk for strong storms would be inland locations.

The onshore winds and heavier cloud cover will keep coastal high temperatures in the mid to upper 80s, whereas inland areas will see highs in the low 90s both days.

LONG TERM /SATURDAY THROUGH WEDNESDAY/

Main Highlights This Period:

- Daily Thunderstorms, Isolated Strong Storms Possible Inland.

A pattern shift is expected on Saturday, steering flow will shift to southwesterly ahead of an incoming cold front from the north, expected to reach the area later this weekend. The southwesterly winds will allow numerous showers and storms to develop Saturday afternoon across all of northeast Florida, including the coast, while southeast Georgia sees more scattered convection. Sunday, storm coverage increases areawide as we see an increase in moisture ahead of the cold front sinking southward. High precipitation chances continue Monday as the front pushes through the area, leaving lower chances on Tuesday as the easterly flow returns. Overall, high temperatures will be in the upper 80s to low 90s.

AVIATION /18Z WEDNESDAY THROUGH 18Z THURSDAY/

Confidence in thunderstorm development this afternoon has decreased, and we have decided to remove vicinity thunderstorm mentions at the regional TAFs at this time. Bands of moderate to heavy showers will continue to shift west and southwestward across the northeast FL terminals, with SGJ most likely to be impacted through around 22Z, where a TEMPO group for IFR conditions during heavier downpours remains in place this afternoon. A TEMPO group also remains in place for GNV through around 22Z, where MVFR conditions are possible during heavier downpours. Thunderstorm probabilities are slightly higher at GNV after 19Z, so please check for amendments through the late afternoon. PROB30 groups for MVFR conditions during heavier downpours were otherwise maintained at the Duval County terminals through around 00Z, with enough confidence to remove the PROB30 group at SSI, where vicinity showers should prevail until around 00Z.

VFR conditions should then prevail this evening and tonight through around 06Z, with vicinity shower possibilities continuing at the northeast FL terminals. Another round of low stratus ceilings is expected to develop at the regional terminals after 06Z, which will provide for IFR to MVFR conditions during the predawn and early morning hours on Thursday. Northeasterly surface winds sustained at 10-15 knots through around 23Z, with speeds then gradually diminishing after sunset this evening, with speeds remaining sustained around 5 knots after 06Z Thursday at the SSI and SGJ coastal terminals and less than 5 knots elsewhere. Easterly surface winds will then increase to 5-10 knots after 14Z at the regional terminals.

MARINE

A trough will progress westward across our local waters this afternoon and evening, providing breezy northeasterly wind and numerous showers and embedded thunderstorms through this evening. Winds will shift to easterly with gradually decreasing speeds later tonight as the trough shifts onshore, with breezy southeasterly winds forecast on Thursday, along with scattered to numerous showers and a few embedded thunderstorms. Weak Atlantic high pressure will then build westward towards the southeastern seaboard on Friday, maintaining a light southeast wind flow that will again produce scattered to numerous showers and a few embedded thunderstorms. Prevailing westerly winds are then expected from Saturday through at least Monday morning as a frontal boundary sinks southward towards our region, with this feature maintaining a stormy weather pattern, especially during the afternoon and evening as activity pushes eastward from coastal locations. Stronger high pressure will build down the southeastern seaboard early next week in the wake of this boundary, likely pushing the front over the northeast Florida waters. Breezy onshore winds will gradually overspread our local waters by Monday afternoon and night.

Rip Currents: A long period east-southeasterly ocean swell will combine with breezy northeasterly winds to create breakers of 3-4 feet at the northeast FL beaches and 2-3 feet at the southeast GA beaches through Thursday. These conditions will yield a high risk of deadly rip currents at the northeast FL beaches and a higher end moderate risk for the southeast GA beaches. The long period swell will gradually fade on Thursday and should not linger into Friday, with the afternoon sea breeze creating enough of an onshore breeze to yield a lower end moderate risk on Friday at area beaches. Prevailing offshore winds this weekend should result in a low risk, while developing onshore winds on Labor Day likely resulting in at least a moderate risk.

FIRE WEATHER

- Patchy Low Dispersions Over North Central Florida Friday.

- LOW DISPERSIONS ALONG THE COAST FRIDAY AND THIS WEEKEND.

Onshore flow continues through midweek bringing early morning showers across coastal locations, and then towards inland locations as the Atlantic sea breeze moves inland. By the afternoon hours, amplified showers and thunderstorms will be possible with diurnal heating. With weaker winds aloft, dispersions will continue to generally be in the poor to fair range much of the week, particularly over north central FL, and coastal locations by this weekend. Moisture advecting in from the Atlantic will help maintain good min RH values across the area.

Fog Potential: Gusty and erratic winds can be expected in and near thunderstorms with briefly localized flooding rainfall. Late night and early morning patchy fog and low stratus will be possible, especially in areas that received more rainfall.

PRELIMINARY POINT TEMPS/POPS

AMG 73 90 73 91 / 10 70 0 60 SSI 78 88 78 88 / 20 60 10 40 JAX 75 89 75 90 / 30 60 10 70 SGJ 76 87 76 89 / 40 50 10 60 GNV 74 90 73 91 / 40 70 30 80 OCF 73 91 74 91 / 40 80 30 80

JAX WATCHES/WARNINGS/ADVISORIES

FL...High Risk for Rip Currents through Thursday evening for FLZ124-125- 138-233-333. GA...None. MARINE...None.